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

OBJECTIVE

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

DESIGN

Case-control study.

SETTING

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

SAMPLE: The cases: 377 women with IUFD.

CONTROLS: 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).

METHODS

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.

MAIN OUTCOME MEASURES: Incidence of IUFD and adjusted odds ratios of risk factors.

RESULTS

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.

CONCLUSION

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.