Incidence and risk factors of fetal death in Norway: a case-control study

To estimate incidence and risk factors for intrauterine fetal death (IUFD) in a Norwegian study-population applying two different control groups.

Case-control study.

Two university hospitals in Oslo, Norway, January 1990 through December 2003.

The cases: 377 women with IUFD.

1) all women delivering at the study-hospitals in the period (facility-based), and 2) 1 215 women with live births at one study-hospital in the period (selected).

Information from cases and selected controls was collected from medical records. Data on facility-based controls were provided by the Medical Birth Registry of Norway. Data were analyzed using chi-squared test and logistic regression.

Incidence of IUFD and adjusted odds ratios of risk factors.

The incidence was 4.1/1 000 deliveries. Small-for-gestational age (SGA) and placental abruption were the strongest risk factors for IUFD. Hypertensive disorders were of low risk if not associated with SGA. Low to moderate risk factors were pre-pregnancy diabetes mellitus, thyroid disease, placenta previa, gestational diabetes, smoking and twin pregnancy. Advanced maternal age was significant when compared with facility-based controls. Risk estimates pointed in the same direction independent of control-group. Hypertension appeared overestimated when using facility-based controls, whereas advanced age was underestimated in the analysis among selected controls.

SGA has a strong association with IUFD, and the risk of hypertensive disorders is mediated through SGA. The other risk factors, except placental abruption, are of low prevalence and of limited importance in the prevention of a relatively low incidence, although dramatic, event like IUFD.