Case-control study of factors associated with intrauterine fetal deaths

To study the characteristics of pregnancies that resulted in stillbirth and to determine which may possibly predict intrauterine fetal death (IUFD).

A total of 161 singleton pregnancies resulting in stillbirth at Nottingham City Hospital from 1991 to 1997 were compared with 499 live births randomly selected from the same period of time. The variables studied were the following: customized birth weight for gestational age, fetal sex, histopathologic cause of IUFD, maternal age, ethnic group, parity, maternal body mass index (BMI), smoking habit, and maternal blood group.

In 54.7% of the cases of stillbirth at our institution women presented with reduction or absence of fetal movements before the diagnosis of IUFD. Almost half of the stillbirths (48.4%) were small for gestational age (< 10th percentile) on the basis of gestational age-specific weight. The difference in customized birth weight between stillbirths and live births was statistically significant (P <.0001). Increased maternal body mass index (BMI) was positively associated with stillbirth rate (P <.001), as was increased maternal age (P =.0012). Women with blood group O (P =.014) had an even higher stillbirth rate. There was no association between stillbirth rate and maternal ethnic group, maternal smoking, maternal Rhesus status, or fetal sex.

This study found that almost half of stillborn babies were small for gestational age. Reduced fetal activity should be investigated thoroughly, with formal measurement of fetal growth as part of this assessment. Maternal blood group and maternal age were found to be important factors in IUFD. Smoking was not confirmed in this study to be a significant factor.