Late preterm, or “near-term,” birth is defined as delivery between 34 and 36 completed weeks’ gestation. According to National Center for Health Statistics in 2002, approximately 60% of all preterm birthswere in this category. The increase in near-term births between 1992 and 2002 was the major contributor to the overall increase in PTB over this time period. Interestingly, this increase came from the Hispanic and nonHispanic White populations, rather than from the Black population which actually experienced a decrease in PTB rates. During the same time period, the rate of deliveries less than 32 weeks' remained relatively constant.
Usually, when we think about short- and long-term complications related to prematurity, this cohort of babies doesn’t show up on the x-ray screens of most healthcare providers. However, there is a growing body of evidence to suggest that these infants have “significantly more medical problems and increased hospital costs compared with contemporaneous full term infants…and may represent an unrecognized at-risk neonatal population.” (Wang, et al., Pediatrics 2004;114:372-6).
Multiple factors are correlated with the rising number of near-term births. For example, there are increasing labor induction rates for indications of maternal medical conditions (such as diabetes and hypertension), "post-dates" pregnancy (now considered anything greater than 41 weeks'), physician convenience (often, but certainly not exclusively, in underserved areas), and patient demand. There are increasing numbers of primary cesarean sections secondary to factors such as the higher induction rates (less favorable cervix to start with, maternal medical conditions, and provider and patient impatience with the induction process), medical-legal concerns of providers for fetal well-being or fetal weight (large or small), reluctance to perform operative vaginal deliveries (forceps and vacuum extraction), and also physician convenience and patient demand.
In addition to the above, there is an increase in the number of women who have delayed child-bearing until age 35 or older, increasing the risks of complications related to infertility, hypertension, diabetes, and other underlying medical conditions. At the same time, there have been rising success rates of assisted reproductive technologies, helping women conceive (generally older women), who otherwise never would have had the opportunity to have children because of infertility or underlying medical conditions, and increasing the number of multiple gestations which, as pointed out in my last post, is an independent risk factor for PTB, particularly between 34 and 37 weeks'. Among other factors, increased stress and substance abuse certainly contribute their share to PTB at later gestational ages as well.
Consequences of near-term delivery include increased initial complications related to respiratory distress, jaundice, feeding difficulties, seizures, hypoglycemia, and sepsis that may require management (admissions and readmissions) to expensive neonatal intensive care units (Raju, et al., Pediatrics 2006;118:1207-14). At this point, we do not have good data to tell us what this means in terms of long-term medical complications, childhood development, and costs of medical and social issues that result from being delivered not quite fully done! It would not surprise me if these turn out to be much greater than previously appreciated.
The purpose of pointing out the magnitude of the problem of near-term birth is that this is one area in which we could have a rapid and significant impact on the incidence of and morbidity associated with PTB. Clearly, education of both patients and healthcare providers is the first step in this process. (For those of you interested in an in-depth evaluation of the current staus of near-term birth, two complete issues of Seminars in Perinatology, 2006;30 (1 and 2) were devoted to this topic in February and April of this year).