Inducing labor at 40 weeks may reduce infant deaths
Research Activities, March 2009, No. 343
When a pregnancy goes to 42 weeks, instead of the typical 40 after the mother's last missed period, doctors usually induce labor. This measure is taken because the placenta, the baby's lifeline, stops providing adequate nutrition and oxygen at that time and this can lead to infant death. A new study suggests that even 41-week-long pregnancies may put an infant at increased risk of death within 28 days after delivery.
Tim A. Bruckner, Ph.D., of the University of California, Berkeley, and colleagues used California Department of Health Services birth data from 1999 to 2003 and found that normal weight infants born between 41 weeks and 42 weeks and 6 days of gestation had a 37 percent greater chance of neonatal death (less than 28 days after birth) compared with infants born at 38 weeks to 40 weeks and 6 days. However, the 37 percent greater risk remained stable between 41 and 42 weeks.
The authors caution that true gestational ages in the study may be in error because the ages were calculated using the date of the mother's last missed period and not with ultrasounds, which are now the gold standard for determining gestational age. California began using ultrasound dating in 2007, and the authors hope researchers will use these data to study this topic when data become available this year. This study was funded in part by the Agency for Healthcare Research and Quality (T32 HS00086).
See "Increased neonatal mortality among normal-weight births beyond 41 weeks of gestation in California," by Dr. Bruckner, Yvonne W. Cheng, M.D., M.P.H., and Aaron B. Caughey, M.D., Ph.D., in the October 2008 American Journal of Obstetrics and Gynecology 199(4), pp. 421.e1-7.