Abstract
BackgroundThe proportions of preterm birth (PTB, ie., delivered before 37 gestational weeks) and low birth weight (LBW, ie., birth weight less than 2500 g at delivery) have been rising in developed countries. We sought to examine the factors contributing to the rise in Japan, with particular focus on the effects of obstetric interventions.MethodsWe used a database maintained by one large regional hospital in Shizuoka, Japan. We restricted the analysis to mothers who delivered live singleton births from 1997 to 2010 (n = 19,221). We assessed the temporal trends in PTB and LBW, then divided the study period into four intervals and compared the proportions of PTB and LBW. We also compared the newborns’ outcomes between the intervals.ResultsPTB, in particular medically indicated PTB, increased considerably. The increase was largely explained by changes in caesarean sections. The neonatal outcomes did not worsen, and instead the Apgar scores and proportions requiring neonatal intensive care unit (NICU) admission improved. In particular, the risks of NICU admission in the interval from 2007 to 2010 were decreased among all births [odds ratio (OR): 0.84; 95% confidence interval (CI): 0.75, 0.95] and medically indicated births (OR: 0.44; 95% CI: 0.29, 0.68) compared with the interval from 1997 to 2000.ConclusionsDespite the increases in PTB as well as LBW, the present study suggests benefits of obstetric interventions. Rather than simple categorization of PTB or LBW, indicators such as perinatal mortality or other outcomes may be more appropriate for evaluation of perinatal health in developed countries.
Highlights
The proportions of preterm birth (PTB, ie., delivered before 37 gestational weeks) and low birth weight (LBW, ie., birth weight less than 2500 g at delivery) have been rising in developed countries
The proportions of Preterm birth (PTB) at less than 37 weeks, medically indicated PTB, and Low birth weight (LBW) increased with peaks around 2005 to 2006, while the proportions of term-LBW and spontaneous PTB showed little change during the study period
Among the increase of PTB at less than 37 weeks, the absolute number of the increase was large for PTB at 34 to 36 weeks, PTB at each gestational week increased to some extent
Summary
The proportions of preterm birth (PTB, ie., delivered before 37 gestational weeks) and low birth weight (LBW, ie., birth weight less than 2500 g at delivery) have been rising in developed countries. Previous studies examined the factors contributing to these rises (in particular PTB), and found that PTB at gestational age from 34 to 36 weeks Despite the increases in PTB and LBW, the infant mortality and neonatal mortality rates have been declining in these developed countries [12] These contrasting trends have raised questions about the simultaneous roles of obstetric interventions as both a contributor to the rise in PTB and to the improvements in PTB-associated mortality [5,7,13,14]. They could only evaluate the impacts on mortality and could not provide more detailed information in terms of biological indicators, such as the Apgar score and cord blood pHs
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