Spontaneous early term delivery associated with subsequent preterm birth

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1. Spontaneous delivery in early term (37-39 weeks) may be associated with subsequent spontaneous preterm labor. 

2. Labor induction of term pregnancies is associated with decreased risk of subsequent spontaneous preterm birth (sPTB). 

Evidence Rating Level: 2 (Good)            

Study Rundown: This study showed that women who went into spontaneous labor in early term (37-39 weeks estimated gestational age) were more likely to experience subsequent spontaneous preterm labor. Results also found that induction of term pregnancies was associated with decreased odds of subsequent sPTB. The present work is the first study to evaluate the association between spontaneous vs. induced labor in term and early term pregnancies with sPTB in subsequent pregnancies.

Limitations of the study include retrospective design and a control group matched only for date and time of delivery. Future studies might include a prospective cohort study and evaluation of trends between groups better matched for other factors that may influence risk of sPTB.

Click to read the study in AJOG

Relevant Reading: Prediction and prevention of recurrent spontaneous preterm birth

Study Author, Dr. Lisa Levine, MD, MSCE, talks to 2 Minute Medicine: University of Pennsylvania, Department of Obstetrics & Gynecology, Division of Maternal & Fetal Medicine

“Our study results are in keeping with the emerging evidence that deliveries in the early term period have outcomes different than deliveries after 39 weeks. The findings from our study give credence to the concept that not all ‘term’ deliveries have the same outcomes, nor do they have the same implications for future pregnancies.”

In-Depth [retrospective cohort study]: This study used medical records of women undergoing induced labor (n=622) and spontaneous labor (n=265) who delivered a second baby at the same hospital to examine whether labor induction (defined as employment of cervical foley, artificial rupture of membranes, prostaglandin and/or pitocin) increases likelihood of sPTB. Outcomes evaluated at the second delivery were spontaneous labor and delivery or premature rupture of membranes at <37 weeks gestation, mode of delivery, and sPTB at <34 weeks and <24 weeks.

Women who required labor induction for delivery at the index pregnancy were less likely to experience sPTB (OR 0.55, CI 0.31-0.97). In women who experienced spontaneous onset of labor, those who spontaneously delivered early term (37-39wga) pregnancies were more likely to experience subsequent sPTB (OR 3.0, CI 1.44-6.16, p=0.003), while those who delivered spontaneously after 38.9wga were no less likely (p=0.8).

By Denise Pong, MPH and Leah Hawkins, MD, MPH

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