Delivery at 39 Weeks of Gestation: The Time Has Come

Clinical Factors Associated with Intrapartum Presentation Change after Mechanical Cervical Ripening

OBJECTIVE

 The use of mechanical cervical ripening with balloon devices is common during induction of labor; however, there is risk for displacement of the fetal presenting part during its insertion. This study sought to investigate the clinical risk factors associated with an intrapartum presentation change from cephalic to noncephalic presentation after mechanical cervical ripening.

STUDY DESIGN

 Data were obtained from the Consortium on Safe Labor, a multicenter retrospective study that abstracted detailed labor and delivery information from electronic medical records in 19 hospitals across the United States. All women with fetal cephalic confirmed position on admission undergoing induction of labor with mechanical cervical ripening were included. Women who had a cesarean delivery for noncephalic presentation were compared with women who had a vaginal delivery or cesarean delivery for other indications. Models were adjusted for nulliparity, multiple gestation, and gestational age.

RESULTS

 A total of 3,462 women met inclusion criteria, with 1.3% (n = 46) having an intrapartum presentation change from cephalic to noncephalic presentation after mechanical cervical ripening. Those who had a cesarean delivery for an intrapartum presentation change were more likely to be nulliparous (82.6 vs. 65.4%, p = 0.01), less than 34 weeks' gestation (6.5 vs. 1.3%, p = 0.02), and have twins (6.5 vs. 1.2%, p = 0.02). In adjusted analysis, twins were associated with an increased odds of cesarean delivery for intrapartum presentation change (adjusted odds ratio [aOR]: 4.43; 95% confidence interval [CI]: 1.25-15.77), whereas multiparity reduced the odds (aOR: 0.38; 95% CI: 0.17-0.82).

CONCLUSION

 Nulliparity and multifetal gestation are associated with a cesarean delivery for an intrapartum presentation change after mechanical cervical ripening.

KEY POINTS

· Intrapartum presentation change after mechanical cervical ripening is low at 1.3%.. · Nulliparity and multifetal gestation are associated with a cesarean delivery for presentation change.. · There were no significant differences in neonatal morbidity by delivery status to delivery type..

Time of delivery among low-risk women at 37-42 weeks of gestation and risks of stillbirth and infant mortality, and long-term neurological morbidity

BACKGROUND

The most important knowledge gap in connection with obstetric management for time of delivery in term low-risk pregnancies relates to the absence of information on long-term neurodevelopmental outcomes.

OBJECTIVES

We examined risks of stillbirth, infant mortality, cerebral palsy (CP) and epilepsy among low-risk pregnancies.

METHODS

In this population-based Swedish study, we identified, from 1998 to 2019, 1,773,269 singleton infants born between 37 and 42 completed weeks in women with low-risk pregnancies. Poisson log-linear regression models were used to examine the association between gestational age at delivery and stillbirth, infant mortality, CP and epilepsy. Adjusted rate ratios (RR) and 95% confidence intervals expressing the effect of birth at a particular gestational week compared with birth at a later gestational week were estimated.

RESULTS

Compared with those born at a later gestation, RRs for stillbirth and infant mortality were higher among births at 37 weeks' and 38 weeks' gestation. The RRs for infant mortality were approximately 20% and 25% lower among births at 40 or 41 weeks compared with those born at later gestation, respectively. Infants born at 37 and 38 weeks also had higher RRs for CP (vs infants born at ≥38 and ≥39 weeks, respectively), while those born at 39 gestation had similar RRs (vs infants born at ≥40 weeks); infants born at 40 and 41 weeks had lower RRs of CP (vs those born at ≥41 and 42 weeks, respectively). The RRs for epilepsy were higher in those born at 37 and 38 weeks compared with those born at later gestation.

CONCLUSIONS

Among low-risk pregnancies, birth at 37 or 38 completed weeks' gestation is associated with increased risks of stillbirth, infant mortality and neurological morbidity, while birth at 39-40 completed weeks is associated with reduced risks compared with births at later gestation.

Sonoelastographic Assessment of the Uterine Cervix in the Prediction of Imminent Delivery in Singleton Nulliparous Women Near Term: A Prospective Cohort Study

OBJECTIVES

To explore the role of newly developed software to assess cervical sonoelastography in predicting the onset of spontaneous delivery in singleton pregnancies at term and to compare its diagnostic performance with that provided by the cervical length (CL) and posterior cervical angle (PCA).

METHODS

This work was a prospective study including nulliparous singleton pregnancies at gestational ages of 37 weeks to 38 weeks 6 days. The CL, PCA, hardness ratio (HR), and mean strain from the internal os and external os were obtained by a transvaginal ultrasound approach using semiautomatic software (E-Cervix; Samsung Medison Co, Ltd, Seoul, Korea). Multivariate logistic regression and area under the curve analyses were used to test the strength of the association and the diagnostic performance of the variables considered in predicting delivery within 7 days.

RESULTS

A total of 398 women were included, and 24.6% delivered within 7 days. The CL was shorter (19.5 versus 2 7 mm; P = .0001), PCA narrower (99° versus 102°; P = .02) HR lower (35.3 versus 40.7; P = .0001), mean strain from the external os higher (0.41 versus 0.35; P = .0001), and mean strain from the internal os higher (0.38 versus 0.33; P = .0001) higher in women who delivered within 7 days from the assessment. At the multivariable logistic regression analysis, the CL (adjusted odds ratio, 1.307) and HR (adjusted odds ratio, 1.227) were the only variables independently associated with delivery within 1 week. A model combining the CL and HR showed an area under the curve of 0.873 in predicting delivery within 7 days, higher than that obtained by using the CL and HR singularly (P ≤ .0001).

CONCLUSIONS

The HR assessed by sonoelastography improves the efficacy of the CL in predicting imminent delivery in nulliparous women close to term.

Prediction of delivery after 40 weeks by antepartum ultrasound in singleton nulliparous women: a prospective cohort study

BACKGROUND

Induction of labor at 39 weeks of gestation is associated with better maternal and perinatal outcomes than expectant management. However, a policy of induction of labor implies the identification of women who will deliver after 40 weeks, who are at higher risk of adverse outcome.

OBJECTIVE

This study primarily aimed to elucidate the role of antepartum ultrasound in predicting the onset of spontaneous labor in a cohort of low-risk singleton pregnancies, and secondarily to compare its diagnostic performance with that of other ultrasonographic and clinical parameters.

STUDY DESIGN

This was a prospective study including singleton nulliparous women undergoing a dedicated ultrasound assessment at 36 to 38 weeks of gestation. The primary outcome was delivery ≥40 weeks of gestation. The ultrasound parameters explored were cervical length, posterior cervical angle, angle of progression, and head-perineum distance. Multivariate logistic regression, Kaplan-Meier, and area under the curve analyses were used to test the strength of association and diagnostic performance of variables considered in predicting delivery ≥40 weeks.

RESULTS

A total of 457 women were included, and 49.2% delivered ≥40 weeks. Cervical length was longer (30 vs 19 mm; P≤.0001) and posterior cervical angle wider (105° vs 98°, P≤.0001) in women delivering ≥40 weeks than those delivering <40 weeks. Similarly, head-perineum distance was longer (48 vs 40 mm; P=.001) and angle of progression narrower (93° vs 95°; P=.04) in pregnancies delivering after 40 weeks. Conversely, there was no difference in the modified Bishop score between the 2 study groups (P=.689). In multivariable logistic regression analysis, cervical length (adjusted odds ratio, 1.307) and head-perineum distance (adjusted odds ratio, 1.227) were independently associated with delivery ≥40 weeks. Cervical length showed an area under the curve of 0.896 in predicting a delivery after 40 weeks. Integration of head-perineum distance in the diagnostic algorithm did not increase the performance of the model. A cervical length of 24 mm at 36 to 37 weeks of gestation showed the best combination of sensitivity and specificity in predicting delivery ≥40 weeks, with a shorter latency between ultrasound assessment and birth.

CONCLUSION

Antepartum ultrasound can reliably identify a subset of nulliparous women at higher risk of delivering beyond 40 weeks. A cervical length >24 mm at 36 to 37 weeks of gestation shows the optimal combination of sensitivity and specificity in predicting delivery ≥40 weeks. The findings from this study can help in identifying those women for whom elective induction of labor at 39 weeks of gestation would be beneficial in reducing the risk of adverse pregnancy outcome.