Which obstetric history findings are risk factors for recurrent preterm labor?

Updated: May 04, 2021
  • Author: Michael G Ross, MD, MPH; Chief Editor: Carl V Smith, MD  more...
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A history of prior preterm deliveries places the patient in the high-risk category. Of the predictors of preterm birth, past obstetric history may be one of the strongest predictors of recurrent preterm birth. Given a baseline risk of 10-12%, the risk of recurrent preterm birth after 1, 2, and 3 consecutive preterm births may be increased to approximately 15%, 30%, and 45%, respectively. Preconceptual counseling should help encourage patients to make informed decisions concerning future pregnancy in light of prematurity risk in the presence of previous preterm delivery. Often the best time to counsel the patient is at her 4- to 6-week postpartum check after a preterm delivery.

Lykke et al found that spontaneous preterm delivery, preeclampsia, or fetal growth deviation in a first singleton pregnancy predisposes women to those complications in their second pregnancy, especially if the complications were severe. In a registry-based cohort study of 536,419 Danish women, delivery between 32 and 36 weeks of gestation increased the risk of preterm delivery in the second pregnancy from 2.7% to 14.7% (odds ratio [OR] 6.12; 95% confidence interval [CI], 5.84-6.42) and increased the risk of preeclampsia from 1.1% to 1.8% (OR 1.60; 95% CI, 1.41-1.81). A first delivery before 28 weeks increased the risk of a second preterm delivery to 26.0% (OR 13.1; 95% CI, 10.8-15.9) and increased the risk of preeclampsia to 3.2% (OR 2.96; 95% CI, 1.80-4.88).

The optimal method of preventing preterm birth in multiple gestations has yet to be proven. Cervical cerclage, prophylactic bed rest, and empiric use of tocolytics have not been successful. Most recently, a randomized controlled trial by Lim et al suggests that the use of 17α-hydroxyprogesterone caproate does not prevent neonatal morbidity or preterm birth in multiple pregnancies. [8]

Preeclampsia in a first pregnancy with delivery between 32 and 36 weeks increased the risk of preeclampsia in a second pregnancy from 14.1% to 25.3% (OR 2.08; 95% CI, 1.87-2.31) and increased the risk for a small for gestational age infant from 3.1% to 9.6% (OR 2.82; 95% CI, 2.38-3.35). Fetal growth 2 to 3 standard deviations below the mean in a first pregnancy increased the risk of preeclampsia from 1.1% to 1.8% (OR 1.62; 95% CI, 1.34-1.96) in the second pregnancy. [9] See the Gestational Age from Estimated Date of Delivery calculator.

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