Advanced Maternal Age (AMA) Is An Independent Predictor Of Intrauterine Fetal Death At Term

September 13, 2007

SMFM 27th Annual Meeting 2007


Objective: AMA is associated with an increased risk of complications of pregnancy, such as gestational diabetes, preeclampsia, and placenta previa. Antepartum surveillance has reduced intruterine fetal death (IUFD) rates in some circumstances. We sought to determine if AMA was an independent predictor of IUFD, and if so, at what maternal age antenatal testing may have the greatest impact.

Study Design: We conducted a cross-sectional study using US CDC perinatal mortality data from 1995-1997 comprised of 11,061,599 singleton deliveries. Women from 15 to 44 years of age with term (≥ 37 weeks), singleton pregnancies were included in the analysis. Cox proportional hazards models and logistic regression analysis were used for relative risk estimation and 95% confidence interval (CI) calculation. Number needed to treat (NNT) was calculated based on known IUFD rates, on the assumption that antenatal testing would reduce the risk of IUFD to that of the referent group.

Results: After excluding congenital anomalies and maternal medical complications, 6,239,399 singleton, term deliveries were identified. When compared to the referent group (maternal age 25 to 29), the risk of IUFD increased with advancing maternal age: 30 to 34 RR = 1.24 (95% CI, 1.13-1.36); 35 to 39 RR = 1.45 (95% CI, 1.21-1.74), and 40 to 44 RR = 3.04 (95% CI, 1.58-5.86). Time to event analysis indicated that the risk of IUFD significantly increased beginning at 38 weeks gestation. Our model suggests that for ages 35 to 39, initiation of fetal testing at 38 weeks of gestation would require approximately 3126 women to have antepartum surveillance to prevent one IUFD, as opposed to only 553 tests for maternal age 40 to 44 years.

Conclusion: AMA is an independent risk factor for IUFD. The cumulative risk of IUFD at 38 weeks of gestation in an uncomplicated patient age 40 and over is similar to the risk of IUFD at 41 weeks in an uncomplicated patient less than age 35. These results support routine antenatal testing beginning at maternal age 40, and started at 38 weeks gestation.


0002-9378/$ - see front matter


American Journal of Obstetrics and Gynecology

Volume 195, Issue 6, Supplement S (December 2006)