In labouring nulliparous women, delivery beyond 39 weeks may be linked with higher odds of adverse maternal outcomes, researchers reported last month.
Their findings are from a secondary analysis of data from a trial of foetal pulse oximetry in spontaneously labouring or induced nulliparous women at or beyond 36 weeks' gestation.
In a December online paper in the American Journal of Obstetrics and Gynecology, Dr Alan Thevenet N. Tita of the University of Alabama at Birmingham and colleagues said that as gestational age rose from 39 to 41 or more completed weeks, there was a significant increase in the risk of reaching a composite maternal outcome of treated uterine atony, blood transfusion, or peripartum infection.
For 40 weeks, compared to 39 weeks, the adjusted odds ratio was 1.29. At 41 weeks and beyond, it was 2.05. For cesarean delivery the odds ratios for the composite endpoint were 1.28 at 40 weeks and 1.75 at 41 weeks and beyond. Adjust odds ratios for a neonatal composite endpoint of death, neonatal respiratory and other morbidities and neonatal ICU admission, were 1.25 at 40 weeks and 1.37 at 41 weeks or later.
Thus, say the investigators, "Risks of maternal morbidity and caesarean delivery but not neonatal morbidity increased significantly beyond 39 weeks."
They point out that "maternal and perinatal outcomes may be improved by delivery soon after 39 0/7 weeks of gestation. However, we do not believe a change in practise is justifiable on the basis of this study or other observational studies considering their limitations."
These and other findings, they conclude "underscore the need for a large randomised trial of a policy of elective delivery at 39 weeks vs. the standard policy of expectant management until at least 41 completed weeks."
"Such a study is important," the researchers add, "given the increasing induction in the United States and the ongoing temporal decrease in the proportion of women who deliver at 40 weeks or later from 48% in 1990 to 33% in 2007."
(Reuters Health, January 2012)
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