General Obstetrics and Gynecology: Obstetrics
Factors associated with nonanomalous stillbirths: The Utah Stillbirth Database 1992-2002

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Objective

This study was undertaken to characterize risk factors associated with nonanomalous stillborn (SB) infants and to ascribe the probability of fetal survival by gestational age among high-risk pregnancies.

Study design

We compiled a database of all SB infants and an equivalent number of controls using information obtained from Utah Birth and Fetal Death Certificates during the years 1992 through 2002. Adjusted and unadjusted odds ratios for risk factors associated with SB were generated. Cox proportional hazard models were used to generate survival curves comparing pregnancies complicated by chronic hypertension or gestational hypertension with those of controls.

Results

Infants with major anomalies were eliminated from both cases and controls, to generate 1566 nonanomalous SBs and 2720 nonanomalous controls. In a logistic regression model controlling for multiple maternal and fetal factors, placental abruption, hydramnios, cord prolapse, and essential hypertension were associated with an increased risk of SB. In pregnancies complicated by essential hypertension, the survival curve diverged from that of controls at those gestational ages approaching term (hazard ratio 2.24; 95% CI 1.52-3.32).

Conclusion

SB in nonanomalous infants in Utah is more common among pregnancies complicated by placental abruption, hydramnios, cord prolapse, and essential hypertension.

Section snippets

Material and methods

Through the Utah Department of Health–Center for Health Data, we compiled a database of all SB infants and an equivalent number of randomly selected controls from a secondary database over the interval 1992 through 2002 using vital statistics obtained from Certificates of Live Birth and Fetal Death Certificates. Information regarding maternal medical risk factors, duration of prenatal care, ethnic background, polysubstance use, education, maternal body habitus, antepartum procedures, method of

Unadjusted ORs

Throughout the period of 1992 through 2002, there were a total of 2795 SBs; a combined database was generated with an equivalent number (1:1) of randomly identified controls using Certificates of Live Births to avoid limiting the detection of sparse associations with the outcome of interest via an overabundance of controls to cases. After elimination of infants with major anomalies from both cases and controls, 1586 SB infants and 2720 controls were available for analysis. A comparison of cases

Comment

We have developed a large population-based and comprehensive database of SBs with controls. Although this database clearly bears all the limitations inherent to those derived from Vital Statistic records (Certificates of Live Birth and Certificate of Fetal Death), because of its size we are able to use logistic regression modeling and Cox proportional hazards to control for potential confounding variables. However, we acknowledge that by using vital statistic records, our dataset may be limited

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Dr Branch holds the H. A. & Edna Benning Presidential Endowed Chair in Obstetrics and Gynecology.

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