Hypertension during pregnancy in South Australia, Part 1: pregnancy outcomes

Abstract

Background: There have been conflicting reports about pregnancy outcome in the hypertensive disorders of pregnancy. The present study was undertaken to examine outcomes using a population database. Aims: To examine for differences in a range of pregnancy outcomes between three different groups of hypertensive women and normotensive women in South Australia. Methods: Nine pregnancy outcomes were compared for 70 386 singleton pregnancies in the South Australian perinatal data collection in 1998–2001, consisting of 639 women with pre-existing hypertension, 5356 women with pregnancy hypertension, 448 women with superimposed pre-eclampsia and 63 943 normotensive women. Means for the four groups were calculated for birthweight, gestational age, the baby's and mother's length of stay. The groups were also compared for perinatal deaths with an earlier period, 1991–1997. Results: While all three hypertensive groups had high incidences of induction of labour and emergency Caesarean, only pre-existing hypertension and superimposed pre-eclampsia were significantly associated with elective Caesarean section. All hypertensive groups had increased risks for low birthweight and preterm birth and special and neonatal intensive care. Uncomplicated pre-existing hypertension was not associated with small for gestational age infants, but with preterm delivery between 32 and 36 weeks’ gestation. Superimposed pre-eclampsia had the worst prognosis for perinatal and maternal morbidity. While pregnancy hypertension held the intermediate position, it was not associated with an increase in perinatal mortality. The perinatal mortality rate for women with hypertensive disorders in 1998–2001 was significantly lower than that of an earlier period and equivalent to that for normotensive women. Conclusions: Superimposed pre-eclampsia occurs in approximately 40% of pregnancies of women with pre-existing hypertension and has the most severe outcomes. The hypertensive disorders are associated with high levels of morbidity and intervention, but the high perinatal mortality associated with these disorders has fallen significantly.