130: The prospective risk of stillbirth varies in viable pregnancies by maternal age, parity, and pre-pregnancy body mass index (BMI)


      Unexplained stillbirth remains the largest contributor to perinatal mortality in the Western world; its etiology is frequently unknown, but likely varies by gestational age (GA) and maternal characteristics. Our purpose was to examine the influence of GA and maternal characteristics on prospective risk of stillbirth.

      Study Design

      Retrospective cohort of all women from 2000-2003 with a Utah live birth or stillbirth certificate of a singleton non-anomalous pregnancy. Prospective stillbirth risk was calculated by dividing the number of undelivered patients destined to have a stillbirth by the total number of undelivered patients at 1 week GA increments. Ongoing pregnancies were assumed viable until the gestational week the stillbirth was delivered. Data were stratified by delivery GA, maternal age, parity, and prepregnancy BMI; prospective risk was calculated for each group.


      186,724 live births and 772 stillbirths met inclusion criteria. Likelihood of stillbirth was highest at 20 weeks gestation, and fell steadily until rising sharply at 40-41 weeks. Women of advanced maternal age (AMA) 35 years, primigravidas, and overweight/obese women (BMI 25) had an increased prospective risk of stillbirth throughout gestation when compared with the entire population.
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      Overweight/obese, primigravid, and AMA women had a higher prospective stillbirth risk throughout pregnancy. These population based data are important when counseling patients and considering further investigations of this devastating complication.