据7月28日刊JAMA 上的一项研究披露，对超过20万例的分娩情况的分析发现，与那些足月产的婴儿相比，那些在妊娠 34周至37周间出生的孩子更容易罹患严重的呼吸系统疾病，而在后期早产中，每增加一周的妊娠时间都会使该风险递减。
后期早产（即妊娠期为34 0/7 至 36 6/7 周）在美国占了所有分娩中的9.1%以及所有早产中的四分之三。 根据文章的背景资料，有相当多的证据提示，其所造成的短期性疾病是普遍的，然而，该证据的大多数的支持性的数据都已超过10年的时间，或是来自于小型的群体。
University of Illinois at Chicago的Judith U. Hibbard, M.D.及其在 Consortium on Safe Labor的同僚开展了一项研究，旨在通过分析来自某一大群的后期早产婴儿的最近的数据来测定后期早产儿中呼吸性疾病的目前的发病率。 该研究包括了从12个机构（19所医院）中所收集到的来自全美国的电子化数据，该数据涵盖了在2002年至2008年期间的23万3844例分娩。 所有罹患呼吸性疾病并被NICU（新生儿加护病房）收治的新生儿的病例被抽取出来，研究人员对后期早产儿与足月儿在复苏术使用、呼吸支持、呼吸性疾病诊断等方面进行了比较。
在1万9334例后期早产儿中，有7055例（占36.5%）被NICU 收治，有2032例发生呼吸性疾病。 在16万5993例足月产婴儿中，有1万1980例（占7.2%）被NICU 收治，有1874例罹患呼吸性疾病。 研究人员发现，呼吸窘迫综合症（RDS；这是新生儿的一种急性肺病）是最常见的呼吸性疾病；它在34周分娩的婴儿中占了10.5%（n=390），这一数字会随着妊娠期的增加而下降，在妊娠38周的时候，该数字为0.3%（n=140/41,764）。 新生儿短暂性的呼吸急促是排第二位的最常见疾病，它在34周的时候占6.4%（n=236），并在第39周的时候达到0.3%的低水平（n = 207/ 62,295）。 从妊娠34周开始逐渐下降的还有肺炎（从1.5%至39周时的0.1%）及总体性呼吸衰竭（从1.6%下降至40周时的0.09%）。 随着妊娠期的增加直至39-40周，婴儿罹患不同呼吸性疾病的百分比发生了显著的下降。
额外的分析发现，对那些在妊娠34周出生的新生儿来说，他们发生RDS 的几率增加了40倍，而该风险会随着妊娠期的每递增一周而递减，直至妊娠第38周。 文章的作者写道：“即使在妊娠第37周时的早产儿， 其罹患RDS的几率仍然比妊娠39-或40-周出生的婴儿要高3倍。类似的模式还看见于新生儿短暂性呼吸急促、肺炎、标准性或高频呼吸机需求及呼吸衰竭。”
推荐原文出处：
JAMA. 2010;304(4):419-425. doi:10.1001/jama.2010.1015
Respiratory Morbidity in Late Preterm Births
The Consortium on Safe Labor
Context Late preterm births (340/7-366/7 weeks) account for an increasing proportion of prematurity-associated short-term morbidities, particularly respiratory, that require specialized care and prolonged neonatal hospital stays.
Objective To assess short-term respiratory morbidity in late preterm births compared with term births in a contemporary cohort of deliveries in the United States.
Design, Setting, and Participants Retrospective collection of electronic data from 12 institutions (19 hospitals) across the United States on 233 844 deliveries between 2002 and 2008. Charts were abstracted for all neonates with respiratory compromise admitted to a neonatal intensive care unit (NICU), and late preterm births were compared with term births in regard to resuscitation, respiratory support, and respiratory diagnoses. A multivariate logistic regression analysis compared infants at each gestational week, controlling for factors that influence respiratory outcomes.
Main Outcome Measures Respiratory distress syndrome, transient tachypnea of the newborn, pneumonia, respiratory failure, and standard and oscillatory ventilator support.
Results Of 19 334 late preterm births, 7055 (36.5%) were admitted to a NICU and 2032 had respiratory compromise. Of 165 993 term infants, 11 980 (7.2%) were admitted to a NICU, 1874 with respiratory morbidity. The incidence of respiratory distress syndrome was 10.5% (390/3700) for infants born at 34 weeks' gestation vs 0.3% (140/41 764) at 38 weeks. Similarly, incidence of transient tachypnea of the newborn was 6.4%(n = 236) for those born at 34 weeks vs 0.4% (n = 155) at 38 weeks, pneumonia was 1.5% (n = 55) vs 0.1% (n = 62), and respiratory failure was 1.6% (n = 61) vs 0.2% (n = 63). Standard and oscillatory ventilator support had similar patterns. Odds of respiratory distress syndrome decreased with each advancing week of gestation until 38 weeks compared with 39 to 40 weeks (adjusted odds ratio [OR] at 34 weeks, 40.1; 95% confidence interval [CI], 32.0-50.3 and at 38 weeks, 1.1; 95% CI, 0.9-1.4). At 37 weeks, odds of respiratory distress syndrome were greater than at 39 to 40 weeks (adjusted OR, 3.1; 95% CI, 2.5-3.7), but the odds at 38 weeks did not differ from 39 to 40 weeks. Similar patterns were noted for transient tachypnea of the newborn (adjusted OR at 34 weeks, 14.7; 95% CI, 11.7-18.4 and at 38 weeks, 1.0; 95% CI, 0.8-1.2), pneumonia (adjusted OR at 34 weeks, 7.6; 95% CI, 5.2-11.2 and at 38 weeks, 0.9; 95% CI, 0.6-1.2), and respiratory failure (adjusted OR at 34 weeks, 10.5; 95% CI, 6.9-16.1 and at 38 weeks, 1.4; 95% CI, 1.0-1.9).
Conclusion In a contemporary cohort, late preterm birth, compared with term delivery, was associated with increased risk of respiratory distress syndrome and other respiratory morbidity.
Consortium on Safe Labor Authors: Judith U. Hibbard, MD, Isabelle Wilkins, MD, University of Illinois at Chicago, Chicago; Liping Sun, MD, MS, Division of Epidemiology, Statistics and Prevention Research, National Institute of Child Health and Human Development, Bethesda, Maryland; Kimberly Gregory, MD, Cedars-Sinai Medical Center, Los Angeles, California; Shoshana Haberman, MD, Maimonides Medical Center, Brooklyn, New York; Matthew Hoffman, MD, Christiana Care Health System, Newark, Delaware; Michelle A. Kominiarek, MD, Indiana University Clarian Health, Indianapolis; Uma Reddy, MD, Division of Epidemiology, Statistics and Prevention Research and Pregnancy and Perinatology Branch, National Institute of Child Health and Human Development; Jennifer Bailit, MD, MetroHealth, Case Western Reserve University, Cleveland, Ohio; D. Ware Branch, MD, Intermountain Healthcare and University of Utah, Salt Lake City; Ronald Burkman, MD, Tufts University, Springfield, Massachusetts; Victor Hugo Gonzalez Quintero, MD, University of Miami, Miami, Florida; Christos G. Hatjis, MD, Summa Health System, Akron City Hospital, Akron, Ohio; Helain Landy, MD, Georgetown University Hospital, MedStar Health, Washington, DC; Mildred Ramirez, MD, University of Texas Health Science Center at Houston, Houston; Paul VanVeldhuisen, PhD, EMMES Corp, Rockville, Maryland; James Troendle, PhD, Jun Zhang, PhD, MD, Division of Epidemiology, Statistics and Prevention Research, National Institute of Child Health and Human Development.
