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Obstetrics
The risk of stillbirth and infant death by each additional week of expectant management in twin pregnancies

Presented in oral format at the 35th annual meeting of the Society for Maternal-Fetal Medicine, San Diego, CA, Feb. 2-7, 2015.
https://doi.org/10.1016/j.ajog.2015.03.033Get rights and content

Objective

The objective of the study was to compare the fetal/infant mortality risk associated with each additional week of expectant management with the mortality risk of immediate delivery in women with twin gestations.

Study Design

A retrospective cohort study was performed utilizing 2006–2008 National linked birth certificate and death certificate data. The incidence of stillbirth and infant death were determined for each week of pregnancy from 32 0/7 weeks’ through 40 6/7 weeks’ gestation. Pregnancies complicated by fetal anomalies were excluded. These measures were combined to estimate the theoretic risk of remaining pregnant an additional week by adding the risk of stillbirth during the extra week of pregnancy with the risk of infant death encountered with delivery during the following week. This composite fetal/infant mortality risk was compared with the risk of infant death associated with delivery at the corresponding gestational age.

Results

The risk of stillbirth increased with increasing gestational age, for example, between 37 and 38 weeks’ gestation (12.5 per 10,000 vs 22.5 per 10,000; P < .05). As expected, the risk of infant death following delivery gradually decreased as pregnancies approached term gestation. Week-by-week differences were statistically significant (P < .05) between 32 and 36 weeks with decreasing risk of infant death at advancing gestational ages. The composite risk of stillbirth and infant death associated with an additional week of pregnancy had a significant increase from 37 to 38 weeks’ gestation (43.9 per 10,000 vs 59.2 per 10,000; P < .05). At 37 weeks’ gestation, the relative risk of mortality was statistically significantly lower with immediate delivery as compared with expectant management (relative risk, 0.87; 95% confidence interval, 0.77–0.99).

Conclusion

Our results suggest that fetal/infant death risk is minimized at 37 weeks’ gestation; however, individual maternal and fetal characteristics must also be taken into account when determining the optimal timing of delivery for twin pregnancies.

Section snippets

Materials and Methods

A retrospective cohort study was conducted utilizing 2006-2008 national linked birth certificate and death certificate data. The National Center for Health Statistics links live birth cohort data with infant and fetal death information.1

We utilized stillbirth data at each gestational age week and infant death data following live births at each gestational age week. Data were investigated for twin pregnancies from 20 weeks’ through 42 weeks’ gestational age. Comparisons were made by the

Results

A total of 454,626 twins was included in our analysis of twin gestations with stillbirth or live birth occurring from 32 0/7 through 40 6/7 weeks’ gestational age. Stillbirth was observed in 1585 fetuses (0.35%) and infant death following 2357 live births (0.52%) overall. The risk of stillbirth increased with each additional week of pregnancy (Table 1). However, this increase was statistically significant only between 37 and 38 weeks’ gestation (12.5 per 10,000 vs 22.5 per 10,000) and between

Comment

Our work demonstrates that the risk of immediate delivery is lower than expectant management at 37 weeks’ gestation for unselected twin pregnancies in the absence of fetal anomalies. This corresponds with prior studies that have also recommended this timing of delivery for uncomplicated dichorionic pregnancies.4, 9, 13

When limited to the lower-risk twin pregnancies, excluding gestational diabetes, hypertension, and small-for-gestational-age (SGA)/IUGR pregnancies, 38 weeks became the threshold

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    J.M.S. is supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (grant K99 HD079658-01).

    The authors report no conflict of interest.

    The racing flag logo above indicates that this article was rushed to press for the benefit of the scientific community.

    Cite this article as: Page JM, Pilliod RA, Snowden JM, et al. The risk of stillbirth and infant death by each additional week of expectant management in twin pregnancies. Am J Obstet Gynecol 2015;212:630.e1-7.

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