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早产儿, 免费咨询

早产
其他名称 早产, 早产儿, 早产儿
使用呼吸机的早产儿.jpg
保温箱中插管的早产儿
专业新生儿科, 儿科, 产科
症状 婴儿出生年龄小于 37 周’ 胎龄[1]
脑瘫并发症, 发展迟缓, 听力问题, 视力问题[1]
原因通常未知[2]
危险因素 糖尿病, 高血压, 多胎妊娠, 肥胖或体重不足, 一些阴道感染, 乳糜泻, 吸烟, 心理压力[2][3][4]
预防黄体酮[5]
治疗皮质类固醇, 通过肌肤接触让宝宝保持温暖, 支持母乳喂养, 治疗感染, 支持呼吸[2][6]
频率约每年 1500 万次 (12% 交货数量)[2]
死亡人数 805,800[7]
早产, 也称为早产, 婴儿出生时间少于 37 孕周, 与足月分娩相反 40 几周。[1] 极早早产是在之前 32 周, 早期早产发生在 32-36 周之间, 晚期早产发生在 34-36 周之间’ 妊娠。[8] 这些婴儿也被称为早产儿或俗称早产儿 (美式英语)[9] 或早产儿 (澳大利亚英语).[10] 早产的症状包括子宫收缩频率超过每十分钟一次和/或在分娩前从阴道漏出液体 37 几周。[11] 早产儿患脑瘫的风险更大, 发展迟缓, 听力问题和视力问题。[1] 宝宝出生得越早, 这些风险就越大。[1]

自发性早产的原因通常是未知的。[2] 危险因素包括糖尿病, 高血压, 多胎妊娠 (怀上多个婴儿), 肥胖或体重不足, 阴道感染, 空气污染暴露, 吸烟, 和心理压力。[2][3][12] 为了健康怀孕, 之前不建议进行药物引产或剖宫产 39 除非出于其他医疗原因需要，否则需要几周。[2] 提前分娩可能有某些医学原因，例如先兆子痫。[13]

如果在怀孕期间服用黄体酮激素，则可以预防有早产风险的人。[5] 证据不支持卧床休息的有用性。[5][14] 估计至少 75% 的早产儿通过适当的治疗将存活, 最晚出生的婴儿存活率最高。[2] 对于可能在以下时间段分娩的女性 24 和 37 周, 皮质类固醇治疗可能会改善结果。[6][15] 多种药物, 包括硝苯地平, 可能会延迟分娩，以便母亲可以转移到有更多医疗护理且皮质类固醇更有机会发挥作用的地方。[16] 一旦宝宝出生, 护理包括通过皮肤接触或孵化使婴儿保持温暖, 支持母乳喂养和/或配方奶喂养, 治疗感染, 和支持呼吸。[2] 早产儿有时需要插管。[2]

早产是全世界婴儿死亡的最常见原因。[1] 关于 15 每年有数百万婴儿早产 (5% 到 18% 所有交付的).[2] 晚期早产占 75% 所有早产。[17] 这个比率在不同国家并不一致. 在英国 7.9% 在美国 的婴儿早产 12.3% 的所有出生都发生在之前 37 怀孕周数。[18][19] 大约 0.5% 的出生是极早的围产儿 (20-25 怀孕周数), 这些造成了大部分死亡。[20] 在许多国家, 20 世纪 90 年代至 2010 年代，早产率有所上升。[2] 早产并发症导致 0.81 百万人死亡 2015, 从 1.57 百万 1990.[7][21] 生存机会在 22 几周左右 6%, 当在 23 几周了 26%, 24 周 55% 和 25 几周左右 72%.[22] 没有任何长期困难的生存机会较低。[23

体征和症状

檀香山卡皮欧拉尼医疗中心新生儿重症监护室中，一位新妈妈抱着她的早产儿, 夏威夷
早产的体征和症状包括一小时内出现四次或以上子宫收缩. 与假分娩相反, 真正的临产伴随着宫颈扩张和消失. 还, 妊娠晚期阴道流血, 骨盆压力很大, 或者腹部或背部疼痛可能是早产即将发生的征兆. 阴道排出水样分泌物可能表明婴儿周围的胎膜过早破裂. 虽然胎膜破裂后可能不会进行分娩, 通常分娩表明感染 (绒毛膜羊膜炎) 对胎儿和母亲都构成严重威胁. 在某些情况下, 子宫颈过早扩张，没有疼痛或感觉到收缩, 这样母亲直到分娩过程的最后阶段都不会出现警告信号.

原因
早产的原因主要分为早产引产和自发性早产。.

危险因素
自发性早产的确切原因很难确定，可能是由多种不同因素同时引起的，因为分娩是一个复杂的过程。[24][25] 已确定四种不同的途径可导致早产，并有大量证据: 胎儿性早熟内分泌激活, 子宫过度扩张 (胎盘早剥), 蜕膜出血, 以及宫内炎症或感染。[26]

识别早产高风险的妇女将使卫生服务机构能够为这些妇女及其婴儿提供专门护理, 例如，设有特殊护理婴儿病房（例如新生儿重症监护病房）的医院 (新生儿重症监护室). 在某些情况下, 可能会推迟出生. 风险评分系统被建议作为识别高风险人群的一种方法, 然而, 该领域还没有强有力的研究，因此尚不清楚使用风险评分系统来识别母亲是否会延长妊娠并减少早产数量。[27]

母体因素
风险因素 相对风险[28] 95% 信心
间隔[28]
胎儿纤连蛋白 4.0 2.9–5.5
宫颈长度短 2.9 2.1–3.9
衣原体 2.2 1.0–4.8
社会经济地位低 1.9 1.7–2.2
怀孕期间体重增加或大或小 1.8 1.5–2.3
产妇身高矮 1.8 1.3–2.5
牙周炎 1.6 1.1–2.3
乳糜泻 1.4[29] 1.2–1.6[29]
无症状菌尿 1.1 0.8–1.5
BMI 高或低 0.96 0.66–1.4
优势比
自发性早产史 3.6 3.2–4.0
细菌性阴道病 2.2 1.5–3.1
黑人种族/种族 2.0 1.8–2.2
菲律宾血统[30] 1.7 1.5–2.1
意外怀孕[31]:1 1.5 1.41-1.61
意外怀孕[31]:1 1.31 1.09-1.58
单身/未婚[32] 1.2 1.03–1.28

英格兰和威尔士的早产百分比 2011, 按母亲的年龄以及是否是单胎或多胎.
已确定母亲的危险因素与较高的早产风险有关. 这些包括年龄,[33] 体重指数高或低 (体重指数),[34][35] 两次怀孕之间的时间长度,[36] 先前自发的 (IE。, 流产) 或手术流产,[37][38] 意外怀孕,[31] 未经治疗或未诊断的乳糜泻,[29][4] 生育困难, 热暴露,[39] 和遗传变量。[40]

关于工作类型和体力活动的研究给出了相互矛盾的结果, 但人们认为，压力条件, 苦役, 长时间工作可能与早产有关。[33] 肥胖并不直接导致早产;[41] 然而, 它与糖尿病和高血压有关，而糖尿病和高血压本身就是危险因素。[33] 在某种程度上，这些人可能有潜在的疾病 (IE。, 子宫畸形, 高血压, 糖尿病) 坚持下去. 尝试过以上的情侣 1 年与那些尝试过少于一年的人相比 1 在实现自然受孕前一年，调整后的优势比为 1.35 (95% 置信区间 1.22-1.50) 早产。[42] IVF 后怀孕比超过 10 个月后自然受孕的早产风险更大 1 尝试的一年, 调整后的优势比为 1.55 (95% CI 1.30-1.85).[42]

某些种族也可能有更高的风险. 例如, 在美国. 和英国, 黑人女性的早产率为 15-18%, 是白人人口的两倍多. 由于多种因素，许多黑人女性的早产率较高，但最常见的是大量的慢性压力, 这最终可能导致早产。[43] 成人慢性病并不总是导致黑人女性早产, 这使得早产的主要因素难以确定。[43] 菲律宾人早产的风险也很高, 据信近 11-15% 的菲律宾人出生在美国. (与其他亚洲人相比 7.6% 和白人 7.8%) 还为时过早。[44] 菲律宾人的早产率在世界上排名第八，这证明了菲律宾人是一个很大的风险因素, 唯一名列前茅的非非洲国家 10.[45] 与其他亚洲群体或西班牙裔移民相比，这种差异并未出现，并且仍然无法解释。[33] 基因组成是早产的一个因素. 遗传学是菲律宾人早产风险高的一个重要因素，因为菲律宾人普遍存在导致早产的突变。[44] 内部- 早产风险的跨代增加已被证明。[40] 尚未发现任何单一基因.

婚姻状况与早产风险相关. 一项研究 25,373 芬兰的怀孕情况显示，未婚母亲比已婚母亲早产率更高 (P=0.001).[32] 婚外怀孕总体上与 20% 不良后果总数增加, 即使在芬兰提供免费产妇护理的时候. 魁北克省的一项研究 720,586 出生于 1990 到 1997 研究表明，与普通法婚姻或未婚父母相比，合法结婚母亲的婴儿早产的风险较低。[46][需要更新]

怀孕期间的因素
怀孕期间的药物, 生活条件, 空气污染, 吸烟, 非法药物或酒精, 感染, 或身体创伤也可能导致早产.

空气污染: 居住在空气污染严重的地区是早产的主要危险因素, 包括居住在主要道路或高速公路附近，这些道路或高速公路因交通拥堵而导致车辆排放量较高，或者是排放更多污染物的柴油卡车的路线。[47][48][12] 与早产相关的空气污染最严重的国家位于南亚和东亚, 中东, 北非, 和西撒哈拉以南非洲。[需要引用]

使用刺激卵巢释放多个卵子的生育药物以及通过多个胚胎进行胚胎移植的体外受精已被认为是早产的危险因素. 通常出于医疗原因必须引产; 这些情况包括高血压,[49] 先兆子痫,[50] 母亲糖尿病,[51] 哮喘, 甲状腺疾病, 和心脏病.

怀孕母亲的某些健康状况也可能增加早产的风险. 有些女性存在解剖学问题，导致婴儿无法足月出生. 这些包括子宫颈薄弱或短 (早产的最强预测因素).[52][53][54][49] 怀孕期间阴道出血的女性早产的风险较高. 虽然妊娠晚期出血可能是前置胎盘或胎盘早剥（常见于早产的情况）的征兆，但即使不是由这些情况引起的早期出血也与较高的早产率有关。[55] 羊水量异常的女性, 是否过多 (羊水过多) 或太少 (羊水过少), 也面临着风险。[33] 焦虑和抑郁已被视为早产的危险因素。[33][56]

烟草的使用, 可卡因, 怀孕期间过量饮酒会增加早产的机会. 烟草是怀孕期间最常用的药物，对低出生体重分娩有重大影响。[57] 有先天缺陷的婴儿早产的风险较高。[58]

Passive smoking and/or smoking before the pregnancy influences the probability of a preterm birth. The World Health Organization published an international study in March 2014.[59]

Presence of anti-thyroid antibodies is associated with an increased risk preterm birth with an odds ratio of 1.9 和 95% confidence interval of 1.1–3.5.[60]

Intimate violence against the mother is another risk factor for preterm birth.[61]

Physical trauma may case a preterm birth. The Nigerian cultural method of abdominal massage has been shown to result in 19% preterm birth among women in Nigeria, plus many other adverse outcomes for the mother and baby.[62] 由经过认证/许可或训练有素的按摩治疗师进行的按摩治疗不应与经过充分培训和许可的按摩治疗师或受过培训以在怀孕期间提供按摩的其他重要人员进行的按摩相混淆, 已被证明在怀孕期间有许多积极的结果, 包括减少早产, 减少抑郁, 降低皮质醇, 并减少焦虑。[63]

感染
早产感染的频率与胎龄成反比. 生殖器支原体感染与早产风险增加相关, 和自然流产。[64]

传染性微生物可呈上升趋势, 血源性的, 医源性手术, 或通过输卵管逆行. 从蜕膜开始，它们可能到达羊膜和绒毛膜之间的空间, the amniotic fluid, and the fetus. A chorioamnionitis also may lead to sepsis of the mother. Fetal infection is linked to preterm birth and to significant long-term handicap including cerebral palsy.[65]

It has been reported that asymptomatic colonization of the decidua occurs in up to 70% of women at term using a DNA probe suggesting that the presence of micro-organism alone may be insufficient to initiate the infectious response.

As the condition is more prevalent in black women in the U.S. 和英国, it has been suggested to be an explanation for the higher rate of preterm birth in these populations. It is opined that bacterial vaginosis before or during pregnancy may affect the decidual inflammatory response that leads to preterm birth. The condition known as aerobic vaginitis can be a serious risk factor for preterm labor; several previous studies failed to acknowledge the difference between aerobic vaginitis and bacterial vaginosis, which may explain some of the contradiction in the results.[66]

Untreated yeast infections are associated with preterm birth.[67]

A review into prophylactic antibiotics (given to prevent infection) in the second and third trimester of pregnancy (13–42 weeks of pregnancy) found a reduction in the number of preterm births in women with bacterial vaginosis. These antibiotics also reduced the number of waters breaking before labor in full-term pregnancies, reduced the risk of infection of the lining of the womb after delivery (endometritis), and rates of gonococcal infection. 然而, the women without bacterial vaginosis did not have any reduction in preterm births or pre-labor preterm waters breaking. Much of the research included in this review lost participants during follow-up so did not report the long-term effects of the antibiotics on mothers or babies. More research in this area is needed to find the full effects of giving antibiotics throughout the second and third trimesters of pregnancy.[68]

A number of maternal bacterial infections are associated with preterm birth including pyelonephritis, asymptomatic bacteriuria, 肺炎, and appendicitis. A review into giving antibiotics in pregnancy for asymptomatic bacteriuria (urine infection with no symptoms) 发现这项研究的质量非常低，但它确实表明服用抗生素可以减少早产和低出生体重婴儿的数量。[69] 另一项审查发现，一剂抗生素似乎不如一疗程抗生素有效，但报告一剂抗生素副作用的女性较少。[70] 该综述建议需要更多的研究来发现治疗无症状菌尿的最佳方法。[69]

另一项审查发现，进行常规下生殖道感染检测的孕妇的早产发生率低于仅在出现下生殖道感染症状时进行检测的孕妇。[71] 接受常规检查的女性生下的低出生体重婴儿数量也较少. Even though these results look promising, the review was only based on one study so more research is needed into routine screening for low genital tract infections.[71]

Also periodontal disease has been shown repeatedly to be linked to preterm birth.[72][73] 相比之下, 病毒感染, unless accompanied by a significant febrile response, are considered not to be a major factor in relation to preterm birth.[33]

遗传学
There is believed to be a maternal genetic component in preterm birth.[74] Estimated heritability of timing-of-birth in women was 34%. 然而, the occurrence of preterm birth in families does not follow a clear inheritance pattern, thus supporting the idea that preterm birth is a non-Mendelian trait with a polygenic nature.[75]

诊断
Placental alpha microglobulin-1
Placental alpha microglobulin-1 (PAMG-1) 已成为多项研究的主题，评估其预测有迹象的妇女即将发生自发性早产的能力, 症状, 或暗示早产的主诉。[76][77][78][79][80][81] 在一项研究中，将该测试与胎儿纤连蛋白测试和经阴道超声测量宫颈长度进行了比较, PAMG-1 测试 (商业上称为 PartoSure 测试) 据报道，这是即将自然分娩的单一最佳预测因子 7 患者出现症状的天数, 症状, 或早产投诉. 具体来说, PPV, 或阳性预测值, 的测试是 76%, 29%, 和 30% 用于PAMG-1, fFN 和 CL, 分别 (磷 < 0.01).[82]

胎儿纤连蛋白
胎儿纤连蛋白 (扇子) 已成为一种重要的生物标志物——宫颈或阴道分泌物中存在这种糖蛋白表明绒毛膜和蜕膜之间的边界已被破坏. A positive test indicates an increased risk of preterm birth, and a negative test has a high predictive value.[33] It has been shown that only 1% of women in questionable cases of preterm labor delivered within the next week when the test was negative.[83]

超声波
更多信息: Cervical incompetence
Obstetric ultrasound has become useful in the assessment of the cervix in women at risk for premature delivery. A short cervix preterm is undesirable: A cervical length of less than 25 mm at or before 24 weeks of gestational age is the most common definition of cervical incompetence.[84]

Classification

Stages in prenatal development, with weeks and months numbered from last menstruation
在人类中, the usual definition of preterm birth is birth before a gestational age of 37 complete weeks.[85] In the normal human fetus, several organ systems mature between 34 和 37 周, and the fetus reaches adequate maturity by the end of this period. One of the main organs greatly affected by premature birth is the lungs. The lungs are one of the last organs to mature in the womb; because of this, many premature babies spend the first days and weeks of their lives on ventilators. 所以, a significant overlap exists between preterm birth and prematurity. 一般来说, preterm babies are premature and term babies are mature. Preterm babies born near 37 weeks often have no problems relating to prematurity if their lungs have developed adequate surfactant, which allows the lungs to remain expanded between breaths. Sequelae of prematurity can be reduced to a small extent by using drugs to accelerate maturation of the fetus, and to a greater extent by preventing preterm birth.

预防
Historically efforts have been primarily aimed to improve survival and health of preterm infants (tertiary intervention). Such efforts, 然而, have not reduced the incidence of preterm birth. Increasingly primary interventions that are directed at all women, and secondary intervention that reduce existing risks are looked upon as measures that need to be developed and implemented to prevent the health problems of premature infants and children.[86] Smoking bans are effective in decreasing preterm births.[87]

Before pregnancy
Adoption of specific professional policies can immediately reduce risk of preterm birth as the experience in assisted reproduction has shown when the number of embryos during embryo transfer was limited.[86] Many countries have established specific programs to protect pregnant women from hazardous or night-shift work and to provide them with time for prenatal visits and paid pregnancy-leave. The EUROPOP study showed that preterm birth is not related to type of employment, but to prolonged work (超过 42 hours per week) or prolonged standing (超过 6 每天的小时数).[88] 还, night work has been linked to preterm birth.[89] Health policies that take these findings into account can be expected to reduce the rate of preterm birth.[86] Preconceptional intake of folic acid is recommended to reduce birth defects. There is significant evidence that long-term (> one year) use of folic acid supplement preconceptionally may reduce premature birth.[90][91][92] Reducing smoking is expected to benefit pregnant women and their offspring.[86]

During pregnancy
健康饮食可以在怀孕的任何阶段进行，包括营养调整, 使用维生素补充剂, 和戒烟。[86] 膳食钙含量低的女性补充钙可能会减少包括早产在内的不良后果的数量, 先兆子痫, 和产妇死亡。[93] 世界卫生组织 (WHO) 建议每天补充1.5-2克钙, 适用于饮食中钙含量低的孕妇。[94] 尚未发现补充维生素 C 和 E 可以降低早产率。[95] 产前护理管理中采用不同的策略, 未来的研究需要确定重点是否可以放在高危女性的筛查上, 或扩大对低风险女性的支持, 或者这些方法可以在多大程度上融合。[86] While periodontal infection has been linked with preterm birth, randomized trials have not shown that periodontal care during pregnancy reduces preterm birth rates.[86]

Additional support during pregnancy does not appear to prevent low birthweight or preterm birth.[96]

A review into using uterine monitoring at home to detect contractions and possible preterm births in women at higher risk of having a preterm baby found that it did not reduce the number of preterm births.[97] The research included in the review was poor quality but it showed that home monitoring may increase the number of unplanned antenatal visits and may reduce the number of babies admitted to special care when compared with women receiving normal antenatal care.[97]

Screening of low risk women
Screening for asymptomatic bacteriuria followed by appropriate treatment reduces pyelonephritis and reduces the risk of preterm birth.[98] Extensive studies have been carried out to determine if other forms of screening in low-risk women followed by appropriate intervention are beneficial, including screening for and treatment of Ureaplasma urealyticum, group B streptococcus, Trichomonas vaginalis, and bacterial vaginosis did not reduce the rate of preterm birth.[86] Routine ultrasound examination of the length of the cervix identifies patients at risk, but cerclage is not proven useful, and the application of a progestogen is under study.[86] Screening for the presence of fibronectin in vaginal secretions is not recommended at this time in women at low risk.

Self-care
降低早产风险的自我护理方法包括适当的营养, 避免压力, 寻求适当的医疗护理, 避免感染, 以及早产危险因素的控制 (例如. 长时间站立工作, 一氧化碳暴露, 家庭虐待, 和其他因素). 自我监测阴道 pH 值，如果 pH 值过高则进行酸奶治疗或克林霉素治疗，似乎都能有效降低早产风险。[99][100]

超声波宫颈评估
有初步证据表明，超声测量早产患者的子宫颈长度可以帮助调整管理并导致妊娠延长约 4 天。[101]

降低现有风险
Women are identified to be at increased risk for preterm birth on the basis of their past obstetrical history or the presence of known risk factors. Preconception intervention can be helpful in selected patients in a number of ways. Patients with certain uterine anomalies may have a surgical correction (IE. removal of a uterine septum), and those with certain medical problems can be helped by optimizing medical therapies prior to conception, be it for asthma, 糖尿病, 高血压, 和其他人.

Multiple pregnancies
In multiple pregnancies, which often result from use of assisted reproductive technology, there is a high risk of preterm birth. Selective reduction is used to reduce the number of fetuses to two or three.[102][103][104]

Reducing indicated preterm birth
A number of agents have been studied for the secondary prevention of indicated preterm birth. Trials using low-dose aspirin, 鱼油, 维生素C和E, and calcium to reduce preeclampsia demonstrated some reduction in preterm birth only when low-dose aspirin was used.[86] Even if agents such as calcium or antioxidants were able to reduce preeclampsia, a resulting decrease in preterm birth was not observed.[86]

Reducing spontaneous preterm birth
Reduction in activity by the mother—pelvic rest, limited work, bed rest—may be recommended although there is no evidence it is useful with some concerns it is harmful.[105] Increasing medical care by more frequent visits and more education has not been shown to reduce preterm birth rates.[96] Use of nutritional supplements such as omega-3 polyunsaturated fatty acids is based on the observation that populations who have a high intake of such agents are at low risk for preterm birth, presumably as these agents inhibit production of proinflammatory cytokines. A randomized trial showed a significant decline in preterm birth rates,[106] and further studies are in the making.

抗生素
While antibiotics can get rid of bacterial vaginosis in pregnancy, this does not appear to change the risk of preterm birth.[107] It has been suggested that chronic chorioamnionitis is not sufficiently treated by antibiotics alone (and therefore they cannot ameliorate the need for preterm delivery in this condition).[86]

孕激素
Progestogens—often given in the form of vaginal[108] progesterone or hydroxyprogesterone caproate—relax the uterine musculature, maintain cervical length, and possess anti-inflammatory properties; all of which invoke physiological and anatomical changes considered to be beneficial in reducing preterm birth. Two meta-analyses demonstrated a reduction in the risk of preterm birth in women with recurrent preterm birth by 40–55%.[109][110]

Progestogen supplementation also reduces the frequency of preterm birth in pregnancies where there is a short cervix.[111] A short cervix is one that is less than 25mm, as detected during a transvaginal cervical length assessment in the midtrimester.[112] 然而, progestogens are not effective in all populations, as a study involving twin gestations failed to see any benefit.[113] Despite extensive research related to progestogen effectiveness, 黄体酮类型和给药途径仍存在不确定性。[114]

宫颈环扎术
为分娩做准备, 女性的子宫颈缩短. 早产宫颈缩短与早产有关，可以通过超声检查来检测. 宫颈环扎术是一种外科手术，在宫颈周围缝合以防止其缩短和扩大. 已经进行了大量研究来评估宫颈环扎术的价值，该手术似乎主要对宫颈短和有早产史的女性有帮助。[111][115] 代替预防性环扎术, 怀孕期间可以通过超声检查监测处于危险中的妇女, 当观察到子宫颈缩短时, 可以进行环扎术。[86]

管理 (治疗)

早产于 32 几周和 4 体重为 2,000 g 附着在医疗设备上
Tertiary interventions are aimed at women who are about to go into preterm labor, or rupture the membranes or bleed preterm. The use of the fibronectin test and ultrasonography improves the diagnostic accuracy and reduces false-positive diagnosis. While treatments to arrest early labor where there is progressive cervical dilatation and effacement will not be effective to gain sufficient time to allow the fetus to grow and mature further, it may defer delivery sufficiently to allow the mother to be brought to a specialized center that is equipped and staffed to handle preterm deliveries.[116] In a hospital setting women are hydrated via intravenous infusion (as dehydration can lead to premature uterine contractions).[117]

If a baby has cardiac arrest at birth and is before 23 weeks or less than 400 g attempts at resuscitation are not indicated.[118]

Steroids
Severely premature infants may have underdeveloped lungs because they are not yet producing their own surfactant. This can lead directly to respiratory distress syndrome, also called hyaline membrane disease, in the neonate. To try to reduce the risk of this outcome, pregnant mothers with threatened premature delivery prior to 34 weeks are often administered at least one course of glucocorticoids, a steroid that crosses the placental barrier and stimulates the production of surfactant in the lungs of the baby.[15] Steroid use up to 37 weeks is also recommended by the American Congress of Obstetricians and Gynecologists.[15] Typical glucocorticoids that would be administered in this context are betamethasone or dexamethasone, often when the pregnancy has reached viability at 23 周.

In cases where premature birth is imminent, a second “rescue” course of steroids may be administered 12 到 24 hours before the anticipated birth. There are still some concerns about the efficacy and side effects of a second course of steroids, but the consequences of RDS are so severe that a second course is often viewed as worth the risk. 一个 2015 Cochrane review supports the use of repeat dose(s) of prenatal corticosteroids for women still at risk of preterm birth seven days or more after an initial course.[119]

A Cochrane review from 2020 recommends the use of a single course of antenatal corticosteroids to accelerate fetal lung maturation in women at risk of preterm birth. Treatment with antenatal corticosteroids reduces the risk of perinatal death, neonatal death and respiratory distress syndrome and probably reduces the risk of IVH.[120]

Concerns about adverse effects of prenatal corticosteroids include increased risk for maternal infection, difficulty with diabetic control, and possible long-term effects on neurodevelopmental outcomes for the infants. There is ongoing discussion about when steroids should be given (IE. only antenatally or postnatally too) 以及持续多久 (IE. single course or repeated administration). Despite these unknowns, there is a consensus that the benefits of a single course of prenatal glucocorticosteroids vastly outweigh the potential risks.[121][122][123]

抗生素
The routine administration of antibiotics to all women with threatened preterm labor reduces the risk of the baby to get infected with group B streptococcus and has been shown to reduce related mortality rates.[124]

When membranes rupture prematurely, obstetrical management looks for development of labor and signs of infection. Prophylactic antibiotic administration has been shown to prolong pregnancy and reduced neonatal morbidity with rupture of membranes at less than 34 几周。[125] Because of concern about necrotizing enterocolitis, amoxicillin or erythromycin has been recommended, but not amoxicillin + clavulanic acid (co-amoxiclav).[125]

Tocolysis
A number of medications may be useful to delay delivery including: 非甾体抗炎药, 钙通道阻滞剂, beta mimetics, and atosiban.[126] Tocolysis rarely delays delivery beyond 24–48 hours.[127] This delay, 然而, may be sufficient to allow the pregnant woman to be transferred to a center specialized for management of preterm deliveries and give administered corticosteroids to reduce neonatal organ immaturity. Meta-analyses indicate that calcium-channel blockers and an oxytocin antagonist can delay delivery by 2–7 days, and β2-agonist drugs delay by 48 hours but carry more side effects.[86][128] Magnesium sulfate does not appear to be useful to prevent preterm birth.[129] Its use before delivery, 然而, does appear to decrease the risk of cerebral palsy.[130]

Mode of delivery
The routine use of caesarean section for early delivery of infants expected to have very low birth weight is controversial,[131] and a decision concerning the route and time of delivery probably needs to be made on a case-by-case basis.

Neonatal care

Incubator for preterm baby
In developed countries premature infants are usually cared for in an NICU. The physicians who specialize in the care of very sick or premature babies are known as neonatologists. In the NICU, premature babies are kept under radiant warmers or in incubators (also called isolettes), which are bassinets enclosed in plastic with climate control equipment designed to keep them warm and limit their exposure to germs. Modern neonatal intensive care involves sophisticated measurement of temperature, respiration, 心脏功能, 氧合, and brain activity. 交货后, plastic wraps or warm mattresses are useful to keep the infant warm on their way to the neonatal intensive care unit (新生儿重症监护室).[132] Treatments may include fluids and nutrition through intravenous catheters, oxygen supplementation, mechanical ventilation support, and medications.[133] In developing countries where advanced equipment and even electricity may not be available or reliable, simple measures such as kangaroo care (skin to skin warming), encouraging breastfeeding, and basic infection control measures can significantly reduce preterm morbidity and mortality. Bili lights may also be used to treat newborn jaundice (hyperbilirubinemia).

Water can be carefully provided to prevent dehydration but no so much to increase risks of side effects.[134]

Breathing support
In terms of respiratory support, there may be little or no difference in the risk of death or chronic lung disease between high flow nasal cannulae (HFNC) and continuous positive airway pressure (CPAP) or nasal intermittent positive pressure ventilation (NPPV).[135] For extremely preterm babies (born before 28 周’ gestation), targeting a higher versus a lower oxygen saturation range makes little or no difference overall to the risk of death or major disability.[136] Babies born before 32 weeks probably have a lower risk of death from bronchopulmonary dysplasia if they have CPAP immediately after being born, compared to receiving either supportive care or assisted ventilation.[137]

There is insufficient evidence for or against placing preterm stable twins in the same cot or incubator (co-bedding).[138]

营养
Meeting the appropriate nutritional needs of preterm infants is important for long-term health. Optimal care may require a balance of meeting nutritional needs and preventing complications related to feeding. The ideal growth rate is not known, 然而, preterm infants usually require a higher energy intake compared to babies who are born at term.[139] The recommended amount of milk is often prescribed based on approximated nutritional requirements of a similar aged fetus who is not compromised.[140] An immature gastrointestinal tract (GI tract), 医疗状况 (or co-morbidities), risk of aspirating milk, and necrotizing enterocolitis may lead to difficulties in meeting this high nutritional demand and many preterm infants have nutritional deficits that may result in growth restrictions.[140] 此外, very small preterm infants cannot coordinate sucking, 吞咽, and breathing.[141] Tolerating a full enteral feeding (the prescribed volume of milk or formula) is a priority in neonatal care as this reduces the risks associated with venous catheters including infection, and may reduce the length of time the infant requires specialized care in the hospital.[140] Different strategies can be used to optimize feeding for preterm infants. The type of milk/formula and fortifiers, 给药途径 (by mouth, tube feeding, venous catheter), timing of feeding, quantity of milk, continuous or intermittent feeding, and managing gastric residuals are all considered by the neonatal care team when optimizing care. The evidence in the form of high quality randomized trials is generally fairly weak in this area, and for this reason different neonatal intensive care units may have different practices and this results in a fairly large variation in practice. The care of preterm infants also varies in different countries and depends on resources that are available.[140]

Human breast milk and formula
The American Academy of Pediatrics recommended feeding preterm infants human milk, finding “significant short- and long-term beneficial effects,” including lower rates of necrotizing enterocolitis (NEC).[142] In the absence of evidence from randomised controlled trials about the effects of feeding preterm infants with formula compared with mother’s own breast milk, data collected from other types of studies suggest that mother’s own breast milk is likely to have advantages over formula in terms of the baby’s growth and development.[143][139] When a mother’s breast milk is not available, formula is probably better than donor breast milk for preterm babies in terms of weight gain, linear growth and head growth but there may be little or no difference in terms of neuro-developmental disability, death or necrotising enterocolitis.[144]

Fortified human breast milk and preterm/term formula
Breast milk or formula alone may not be sufficient to meet the nutritional needs of some preterm infants. Fortification of breast milk or formula by adding extra nutrients is an approach often taken for feeding preterm infants, with the goal of meeting the high nutritional demand.[139] High quality randomized controlled trials are needed in this field to determine the effectiveness of fortification.[145] It is unclear if fortification of breast milk improves outcomes in preterm babies, though it may speed growth.[145] Supplementing human milk with extra protein may increase short-term growth but the longer-term effects on body composition, growth and brain development are uncertain.[146][147] Higher protein formula (之间 3 和 4 grams of protein per kilo of body weight) may be more effective than low protein formula (less than 3 grams per kilo per day) for weight gain in formula-fed low-birth-weight infants.[148] There is insufficient evidence about the effect on preterm babies’ growth of supplementing human milk with carbohydrate,[149] 胖的,[150][151] and branched-chain amino acids.[152] 反过来, there is some indication that preterm babies who cannot breastfeed may do better if they are fed only with diluted formula compared to full strength formula but the clinical trial evidence remains uncertain.[153]

Individualizing the nutrients and quantities used to fortify enteral milk feeds in infants born with very low birth weight may lead to better short-term weight gain and growth but the evidence is uncertain for longer term outcomes and for the risk of serious illness and death.[154] This includes targeted fortification (adjusting the level of nutrients in response to the results of a test on the breast milk) and adjustable fortification (adding nutrients based on testing the infant).[154]

Multi-nutrient fortifier used to fortify human milk and formula has traditionally been derived from bovine milk.[155] Fortifier derived from humans is available, 然而, the evidence from clinical trials is uncertain and it is not clear if there are any differences between human-derived fortifier and bovine-derived fortifier in terms of neonatal weight gain, feeding intolerance, 感染, or the risk of death.[155]

Timing of feeds
For very preterm infants, most neonatal care centres start milk feeds gradually, rather than starting with a full enteral feeding right away, 然而, is not clear if starting full enteral feeding early effects the risk of necrotising enterocolitis.[140] 在这些情况下, the preterm infant would be receiving the majority of their nutrition and fluids intravenously. The milk volume is usually gradually increased over the following weeks.[140] Research into the ideal timing of enteral feeding and whether delaying enteral feeding or gradually introducing enteral feeds is beneficial at improving growth for preterm infants or low birth weight infants is needed.[140] 此外, the ideal timing of enteral feeds to prevent side effects such as necrotising enterocolitis or mortality in preterm infants who require a packed red blood cell transfusion is not clear.[156] Potential disadvantages of a more gradual approach to feeding preterm infants associated with less milk in the gut and include slower GI tract secretion of hormones and gut motility and slower microbial colonization of the gut.[140]

Regarding the timing of starting fortified milk, preterm infants are often started on fortified milk/formula once they are fed 100 mL/kg of their body weight. Other some neonatal specialists feel that starting to feed a preterm infant fortified milk earlier is beneficial to improve intake of nutrients.[157] The risks of feeding intolerance and necrotising enterocolitis related to early versus later fortification of human milk are not clear.[157] Once the infant is able to go home from the hospital there is limited evidence to support prescribing a preterm (fortified) formula.[158]

Intermittent feeding versus continuous feeding
For infants who weigh less than 1500 克, tube feeding is usually necessary.[141] Most often, neonatal specialists feed preterm babies intermittently with a prescribed amount of milk over a short period of time. 例如, a feed could last 10-20 minutes and be given every 3 小时. This intermittent approach is meant to mimic conditions of normal bodily functions involved with feeding and allow for a cyclic pattern in the release of gastrointestinal tract hormones to promote development of the gastrointestinal system.[141] 在某些情况下, continuous nasogastric feeding is sometimes preferred. There is low to very low certainty evidence to suggest that low birth weight babies who receive continuous nasogastic feeding may reach the benchmark of tolerating full enteral feeding later than babies fed intermittently and it is not clear if continuous feeding has any effect on weight gain or the number of interruptions in feedings.[141] Continuous feeding may have little to no effect on length of body growth or head circumference and the effects of continuous feeding on the risk of developing necrotising enterocolitis is not clear.[141]

High volume feeds
High-volume (多于 180 mL per Kg per day) enteral feeds of fortified or non-fortified human breast milk or formula may improve weight gain while the pre-term infant is hospitalized, 然而, there is insufficient evidence to determine if this approach improves growth of the neonate and other clinical outcomes including length of hospital stay.[139] The risks or adverse effects associated with high-volume enteral feeding of preterm infants including aspiration pneumonia, reflux, apnoea, and sudden oxygen desaturation episodes have not been reported in the trials considered in a 2021 systematic review.[139]

Parenteral (intraveneous) 营养
For preterm infants who are born after 34 怀孕周数 (“late preterm infants”) who are critically ill and cannot tolerate milk, there is some weak evidence that the infant may benefit from including amino acids and fats in the intravenous nutrition at a later time point (72 hours or longer from hospital admission) versus early (less than 72 hours from admission to hospital), 然而，需要进一步的研究来了解开始静脉营养的理想时机。[159]

胃残留
对于新生儿重症监护中的早产儿，采用强饲法喂养, 监测胃残留物的体积和颜色, 经过一定时间后残留在胃中的乳汁和胃肠道分泌物, 是护理实践的通用标准。[160] 胃残留物常含有胃酸, 荷尔蒙, 酶, 和其他可能有助于改善胃肠道消化和活动的物质. 胃残留物分析可能有助于指导喂养时间。[160] 胃残留增加可能表明喂养不耐受，也可能是坏死性小肠结肠炎的早期征兆. Increased gastric residual may be caused by an underdeveloped gastrointestinal system that leads to slower gastric emptying or movement of the milk in the intestinal tract, reduced hormone or enzyme secretions from the gastrointestinal tract, duodenogastric reflux, formula, 药物, and/or illness.[160] The clinical decision to discard the gastric residuals (versus re-feeding) is often individualized based on the quantity and quality of the residual.[160] Some experts also suggest replacing the fresh milk or curded milk and bile-stained aspirates, but not replacing haemorrhagic residual.[160] Evidence to support or refute the practice of re-feeding preterm infants with gastric residuals is lacking.[160]

Hearing assessment
The Joint Committee on Infant Hearing (JCIH) state that for preterm infants who are in the neonatal intensive care unit (新生儿重症监护室) for a prolonged time should have a diagnostic audiologic evaluation before they are discharged from the hospital.[161] Well babies follow a 1-2-3-month benchmark timeline where they are screened, diagnosed, and receiving intervention for a hearing loss. 然而, very premature babies it might not be possible to complete a hearing screen at one month of age due to several factors. Once the baby is stable an audiologic evaluation should be performed. For premature babies in the NICU, auditory brainstem response (ABR) testing is recommended. If the infant doesn’t pass the screen, they should be referred for an audiologic evaluation by an audiologist.[161] If the infant is on aminoglycosides such as gentamicin for less than five days they should be monitored and have a follow up 6–7 months of being discharged from the hospital to ensure there is no late onset hearing loss due to the medication.[161]

Outcomes and prognosis

Preterm infants survival rates[162][163][164][165][166][167]
Preterm births can result in a range of problems including mortality and physical and mental delays.[168][169]

Mortality and morbidity
In the U.S. where many neonatal infections and other causes of neonatal death have been markedly reduced, prematurity is the leading cause of neonatal mortality at 25%.[170] Prematurely born infants are also at greater risk for having subsequent serious chronic health problems as discussed below.

The earliest gestational age at which the infant has at least a 50% chance of survival is referred to as the limit of viability. As NICU care has improved over the last 40 年, the limit of viability has reduced to approximately 24 几周。[171][172] Most newborns who die, 和 40% of older infants who die, were born between 20 和 25.9 周 (胎龄), during the second trimester.[20]

As risk of brain damage and developmental delay is significant at that threshold even if the infant survives, there are ethical controversies over the aggressiveness of the care rendered to such infants. The limit of viability has also become a factor in the abortion debate.[173]

Specific risks for the preterm neonate
Preterm infants usually show physical signs of prematurity in reverse proportion to the gestational age. 因此, they are at risk for numerous medical problems affecting different organ systems.

Neurological problems include apnea of prematurity, hypoxic-ischemic encephalopathy (HIE), retinopathy of prematurity (ROP),[174] developmental disability, transient hyperammonemia of the newborn, cerebral palsy and intraventricular hemorrhage, the latter affecting 25% of babies born preterm, usually before 32 weeks of pregnancy.[175] Mild brain bleeds usually leave no or few lasting complications, but severe bleeds often result in brain damage or even death.[175] Neurodevelopmental problems have been linked to lack of maternal thyroid hormones, at a time when their own thyroid is unable to meet postnatal needs.[176]
Cardiovascular complications may arise from the failure of the ductus arteriosus to close after birth: patent ductus arteriosus (掌上电脑).
Respiratory problems are common, specifically the respiratory distress syndrome (RDS or IRDS) (previously called hyaline membrane disease). Another problem can be chronic lung disease (previously called bronchopulmonary dysplasia or BPD).
Gastrointestinal and metabolic issues can arise from neonatal hypoglycemia, feeding difficulties, rickets of prematurity, 低钙血症, inguinal hernia, and necrotizing enterocolitis (NEC).
Hematologic complications include anemia of prematurity, 血小板减少症, 和高胆红素血症 (黄疸) that can lead to kernicterus.
感染, including sepsis, 肺炎, and urinary tract infection [1]
一项研究 241 children born between 22 和 25 weeks who were currently of school age found that 46 percent had severe or moderate disabilities such as cerebral palsy, vision or hearing loss and learning problems. Thirty-four percent were mildly disabled and 20 percent had no disabilities, 尽管 12 percent had disabling cerebral palsy.[177][178] 最多 15 出于 100 premature infants have significant hearing loss.[179]

Survival
生存机会在 22 几周左右 6%, 当在 23 几周了 26%, 24 周 55% 和 25 几周左右 72% 截至 2016.[22] With extensive treatment up to 30% of those who survive birth at 22 weeks survive longer term as of 2019.[180] The chances of survival without long-term difficulties is less.[23] Of those who survive following birth at 22 周 33% have severe disabilities.[180] In the developed world overall survival is about 90% while in low-income countries survival rates are about 10%.[181]

Some children will adjust well during childhood and adolescence,[168] although disability is more likely nearer the limits of viability. A large study followed children born between 22 和 25 weeks until the age of 6 岁. Of these children, 46 percent had moderate to severe disabilities such as cerebral palsy, vision or hearing loss and learning disabilities, 34 percent had mild disabilities, 和 20 percent had no disabilities. Twelve percent had disabling cerebral palsy.[178]

As survival has improved, the focus of interventions directed at the newborn has shifted to reduce long-term disabilities, particularly those related to brain injury.[168] Some of the complications related to prematurity may not be apparent until years after the birth. A long-term study demonstrated that the risks of medical and social disabilities extend into adulthood and are higher with decreasing gestational age at birth and include cerebral palsy, intellectual disability, disorders of psychological development, 行为, and emotion, disabilities of vision and hearing, and epilepsy.[182] Standard intelligence tests showed that 41 percent of children born between 22 和 25 weeks had moderate or severe learning disabilities when compared to the test scores of a group of similar classmates who were born at full term.[178] It is also shown that higher levels of education were less likely to be obtained with decreasing gestational age at birth.[182] People born prematurely may be more susceptible to developing depression as teenagers.[183] Some of these problems can be described as being within the executive domain and have been speculated to arise due to decreased myelinization of the frontal lobes.[184] Studies of people born premature and investigated later with MRI brain imaging, demonstrate qualitative anomalies of brain structure and grey matter deficits within temporal lobe structures and the cerebellum that persist into adolescence.[185] Throughout life they are more likely to require services provided by physical therapists, occupational therapists, or speech therapists.[168]

Despite the neurosensory, mental and educational problems studied in school age and adolescent children born extremely preterm, the majority of preterm survivors born during the early years of neonatal intensive care are found to do well and to live fairly normal lives in young adulthood.[186] Young adults born preterm seem to acknowledge that they have more health problems than their peers, yet feel the same degree of satisfaction with their quality of life.[187]

Beyond the neurodevelopmental consequences of prematurity, infants born preterm have a greater risk for many other health problems. 例如, children born prematurely have an increased risk for developing chronic kidney disease.[188]

流行病学

Disability-adjusted life year for prematurity and low birth weight per 100,000 inhabitants in 2004.[189]
没有数据
less than 120
120-240
240-360
360-480
480-600
600-720
720-840
840-960
960-1080
1080-1200
1200-1500
多于 1500
Preterm birth complicates the births of infants worldwide affecting 5% 到 18% of births.[67] In Europe and many developed countries the preterm birth rate is generally 5–9%, 以及在美国. 在过去的几十年里，这一比例甚至上升到了 12-13%。[190]

由于体重比胎龄更容易确定, 世界卫生组织追踪低出生体重率 (< 2,500 克), 发生在 16.5 欠发达地区的出生率 2000.[191] 据估计，这些低出生体重分娩中有三分之一是由于早产. 体重通常与胎龄相关; 然而, 婴儿体重不足可能是由于早产以外的其他原因. 低出生体重新生儿 (低体重) 出生体重小于 2,500 克 (5 磅 8 盎司) 大多数但不限于早产儿，因为它们还包括小于胎龄儿 (SGA) 婴儿. 基于体重的分类进一步识别极低出生体重 (极低体重儿) 小于 1,500 克, 和极低出生体重 (低体重儿) 小于 1,000 g。[192] Almost all neonates in these latter two groups are born preterm.

关于 75% of nearly a million deaths due to preterm deliver would survive if provided warmth, breastfeeding, treatments for infection, and breathing support.[181] 早产并发症导致 740,000 死亡人数 2013, 从 1.57 百万 1990.[21]

社会与文化
经济学
Preterm birth is a significant cost factor in healthcare, not even considering the expenses of long-term care for individuals with disabilities due to preterm birth. 一个 2003 study in the U.S. determined neonatal costs to be $224,400 for a newborn at 500–700 g versus $1,000 at over 3,000 克. The costs increase exponentially with decreasing gestational age and weight.[193] 这 2007 Institute of Medicine report Preterm Birth[194] found that the 550,000 premature babies born each year in the U.S. run up about $26 billion in annual costs, mostly related to care in neonatal intensive care units, but the real tab may top $50 billion.[195]

Notable cases
James Elgin Gill (born on 20 可能 1987 in Ottawa, 安大略省, 加拿大) was the earliest premature baby in the world, until that record was broken in 2004. He was 128 days premature (21 几周和 5 天’ gestation) and weighed 1 pound 6 ounces (624 克). He survived.[196][197]

在 2014, Lyla Stensrud, born in San Antonio, 德克萨斯州, 我们. became the youngest premature baby in the world. She was born at 21 周 4 days and weighed 410 克 (less than a pound). Kaashif Ahmad resuscitated the baby after she was born. As of November 2018, Lyla was attending preschool. She had a slight delay in speech, but no other known medical issues or disabilities.[198]

Amillia Taylor is also often cited as the most premature baby.[199] She was born on 24 十月 2006 in Miami, 佛罗里达, 我们. 在 21 几周和 6 天’ 妊娠。[200] This report has created some confusion as her gestation was measured from the date of conception (through in vitro fertilization) rather than the date of her mother’s last menstrual period, making her appear 2 weeks younger than if gestation was calculated by the more common method.[183] At birth, she was 9 inches (22.9 厘米) long and weighed 10 ounces (280 克).[199] She suffered digestive and respiratory problems, together with a brain hemorrhage. She was discharged from the Baptist Children’s Hospital on 20 二月 2007.[199]

The record for the smallest premature baby to survive was held for a considerable amount of time by Madeline Mann, who was born in 1989 在 26 周, weighing 9.9 ounces (280 克) and measuring 9.5 inches (241.3 毫米) long.[201] This record was broken in September 2004 by Rumaisa Rahman, who was born in the same hospital, Loyola University Medical Center in Maywood, Illinois.[202] 在 25 周’ gestation. At birth, she was 8 inches (200 毫米) long and weighed 261 克 (9.2 盎司).[203] Her twin sister was also a small baby, weighing 563 克 (1 磅 3.9 盎司) 出生时. During pregnancy their mother had pre-eclampsia, requiring birth by caesarean section. The larger twin left the hospital at the end of December, while the smaller remained there until 10 二月 2005 by which time her weight had increased to 1.18 公斤 (2.6 磅).[204] Generally healthy, the twins had to undergo laser eye surgery to correct vision problems, a common occurrence among premature babies.

In May 2019, Sharp Mary Birch Hospital for Women & Newborns in San Diego announced that a baby nicknamed “Saybie” had been discharged almost five months after being born at 23 周’ gestation and weighing 244 克 (8.6 盎司). Saybie was confirmed by Dr. Edward Bell of the University of Iowa, which keeps the Tiniest Babies Registry, to be the new smallest surviving premature baby in that registry.[205]

The world’s smallest premature boy to survive was born in February 2009 at Children’s Hospitals and Clinics of Minnesota in Minneapolis, 明尼苏达州, 我们. Jonathon Whitehill was born at 25 周’ gestation with a weight of 310 克 (11 盎司). He was hospitalized in a neonatal intensive care unit for five months, and then discharged.[206]

在 2020, at the height of the novel Coronavirus pandemic, the worlds most premature baby was born.[207] The baby, named Richard Hutchinson, was born at Children’s Hospitals and Clinics of Minnesota in Minneapolis, 明尼苏达州, 我们. 六月 5, 2020, 在 21 周 2 days gestation. At birth he weighed a remarkable twelve ounces. He remained hospitalized until November 2020, which he was then discharged.[208]

Historical figures who were born prematurely include Johannes Kepler (出生于 1571 at seven months’ gestation), Isaac Newton (出生于 1642, small enough to fit into a quart mug, according to his mother), Winston Churchill (出生于 1874 at seven months’ gestation), and Anna Pavlova (出生于 1885 at seven months’ gestation).[209]

Effect of the coronavirus pandemic
During the COVID-19 pandemic, a drastic drop in the rate of premature births has been reported in many countries, ranging from a 20% reduction to a 90% drop in the starkest cases. Studies in Ireland and Denmark first noticed the phenomenon, and it has been confirmed elsewhere. There is no universally accepted explanation for this drop as of August 2020. Hypotheses include additional rest and support for expectant mothers staying at home, less air pollution due to shutdowns and reduced car fumes, and reduced likelihood of catching other diseases and viruses in general due to the lockdowns.[210]