Dr Dolan is Professor of Clinical Obstetrics & Gynecology and Women’s Health at the Albert Einstein College of Medicine/Montefiore Medical Center, Bronx, New York, and a Medical Advisor to March of Dimes.
Dr McCabe is Senior Vice President and Chief Medical Officer at March of Dimes, White Plains, New York, Distinguished Professor Emeritus, Department of Pediatrics & Inaugural Mattel Executive Endowed Chair of Pediatrics, UCLA School of Medicine, Inaugural Physician-in-Chief, Mattel Children’s Hospital UCLA, and Professor Adjunct, Department of Pediatrics, Yale School of Medicine, New Haven, Connecticut.
Neither author has a conflict of interest to disclose with respect to the content of this article.
The authors thank Motoko Oinuma for assistance with preparation of this article.
Much attention has been paid to the issue of preterm birth (PTB) in recent years due to more than 30 years of unrelenting increases in the annual rate of PTB, from 9.4% in the early 1980s, to 10.6% in 1990, to a peak of 12.8% in 2006
(Figure 1).1 The good news is that the past 7 years have shown a reverse in this trend and modest progress has been made in decreasing the rate of PTB in the United States.
Data from 2013 showed that the US PTB rate decreased for the seventh consecutive year to 11.4%.2 These decreases are good news for newborn health and reflect tremendous progress, with 231,000 fewer babies born preterm and $11.9 billion dollars saved.3
Consequences of PTB
The efforts around PTB prevention have helped clarify gestational age definitions, which are based on neonatal risks (Table 1). The definitions were affirmed by the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine in 2013.4
Ultimately, however, gestational age is a continuous variable. Data show that each week of gestation until full term makes a difference, bringing with it lower mortality rates as well as reduced rates of morbidity and improvement in a variety of health consequences, including respiratory and neurodevelopmental outcomes.5
Analyses from Utah showed an infant mortality rate (per 1000 live births) of 12.5 at 34 weeks, 8.7 at 35 weeks, 6.3 at 36 weeks, 3.4 at 37 weeks, 2.4 at 38 weeks, and 1.2 at 39 weeks.5 Thus, compared to infants born at 40 weeks, those born just 2 weeks earlier (at 38 weeks) were twice as likely to die in the first year of life, and those born at 36 weeks were more than 5 times as likely to die.