Hypertensive disorders in pregnancy and fetal death at different gestational lengths: a population study of 2 121 371 pregnancies.

OBJECTIVE

To compare the proportion of offspring that was stillborn in pregnancies with pre-eclampsia, gestational hypertension or chronic hypertension with those in normotensive pregnancies.

DESIGN

Register-based observational study.

SETTING

The Medical Birth Registry of Norway.

POPULATION

All singleton births after 20 completed weeks of gestation in Norway from 1967 to 2006 (n = 2 121 371).

METHODS

The proportion of stillborn offspring was estimated in normotensive pregnancies, and in pregnancies with pre-eclampsia, gestational and chronic hypertension at different gestational lengths. In addition, changes in the proportions of stillborn offspring by maternal hypertensive disorder from 1967-1986 to 1987-2006 were estimated.

MAIN OUTCOME MEASURES

Fetal death.

RESULTS

The prevalence of hypertensive disorders in pregnancy was 4.7%. In total, 17 933 fetal deaths occurred and 9.2% of these were in hypertensive pregnancies. In normotensive pregnancies, 0.8% (16 290/2 022 400) experienced fetal death. This was true for 1.9% (1170/62 261) of the pregnancies with pre-eclampsia, 1.2% (390/32 068) with gestational hypertension and 1.8% (83/4642) with chronic hypertension. There was a 44% overall reduction in fetal death rate from 1967-1986 to 1987-2006. The largest decline was in women with pre-eclampsia (80% reduction). In women with gestational hypertension and chronic hypertension, the overall reductions in fetal death rates were 49% and 57%, respectively, comparable with the 41% decline in normotensive pregnancies.

CONCLUSIONS

In our nationwide study during 1967-2006, the risk of fetal death among women with hypertensive disorders in pregnancy has been greatly reduced, especially among pre-eclamptic women at term. The risk of fetal death among women with gestational or chronic hypertension has also decreased, but in a different manner.