Research
Obstetrics
The risk of fetal death: current concepts of best gestational age for delivery

Presented in abstract form (abstract no. 537) at the annual meeting of the Society for Maternal-Fetal Medicine, Dallas, TX, Feb. 6-12, 2012.
https://doi.org/10.1016/j.ajog.2012.12.005Get rights and content

Objective

To compare the risk of fetal death (FD) between 34 and 41 weeks' gestational age (GA) with the neonatal mortality rate to examine the best GA for delivery.

Study Design

Linked birth and infant death data for the US from the National Center for Health Statistics analyzed nonanomalous singleton pregnancies between 2003 and 2005. Pregnancies were classified as high risk or low risk based on preexisting maternal complications. Outcomes of 8,785,132 live births and 12,777 FDs between 34 and 42 completed weeks' gestation were examined. The risk of FD was determined using the following equation: #FDthatoccurredatagivenGA+allFDthatoccurredafterthatGATotaldeliveriesatagivenGA+allremainingundeliveredpregnancies

The FD risk of those remaining undelivered was compared with the neonatal death rate for each week of gestation.

Results

Between 34 and 40 weeks' gestation, the FD risk of those remaining undelivered for all pregnancies declined and then increased at term. For high risk pregnancies, the FD risk of those remaining undelivered is substantially higher than for low risk pregnancies. The number of FDs that can be avoided by delivery exceeds the neonatal death rate between 37 and 38 weeks' gestation in low risk pregnancies and at 36 weeks' gestation in high risk pregnancies.

Conclusion

These findings suggest that delivery at 39 weeks' gestation in both high and low risk pregnancies would result in an increased number of perinatal deaths. Decisions regarding the “optimal time for delivery” should include the risk of remaining undelivered.

Section snippets

Materials and Methods

This is a retrospective cohort analysis of the NCHS files on FD data and cohort-linked birth and infant death data for 2003-2005. Analyses were limited to singleton pregnancies delivered between 34 and 42 completed weeks' gestation. Multifetal gestations, fetal anomalies, and cases with missing or unknown variables for fetal anomalies or maternal medical conditions were excluded. In addition, cases with a birthweight inconsistent with the recorded GA were excluded according to the methods

Results

From 2003-2005, a total of 12,522,109 deliveries occurred in the United States, of which there were 12,360,994 live births and 161,115 FDs. Figure 1 depicts the number of deliveries that were excluded from this analysis because of the previously listed criteria. A total of 8,797,909 deliveries were used for our primary analysis with 8,785,132 (99.9%) live births and 12,777 (0.1%) FDs. These deliveries were further divided into HR and LR cohorts based on the presence or absence of preexisting

Comment

Using the NCHS data, we were able to examine the risk of FD and the NDR at each GA for a large cohort of singleton pregnancies in the United States. The analysis quantifies the fetal risk of being undelivered in the general population, and separately for HR and LR cohorts. The results demonstrate that the number of stillbirths occurring for patients who remain undelivered exceeds the number of neonatal deaths that would ensue from delivery of all subjects by 37-38 weeks' gestation. This finding

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    The authors report no conflict of interest.

    Reprints not available from the authors.

    Cite this article as: Mandujano A, Waters TP, Myers SA. The risk of fetal death: current concepts of best gestational age for delivery. Am J Obstet Gynecol 2013;208:207.e1-8.

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