Hypertensive disorders in pregnancy: a population‐based study

Abstract

Objectives:To determine population-based rates and outcomes of hypertensive disorders in pregnancy. Design: Cross-sectional study using linked population databases. Setting and participants: All women, and their babies, discharged from hospital following birth in New South Wales, between 1 January 2000 and 31 December 2002. Main outcome measures: Rates of hypertensive disorders in pregnancy, maternal and infant morbidity and mortality, and level of hospital care for the birth admission. Results: 250 173 women and their 255 931 infants were included in the study. Overall, 24 517 women (9.8%) had a hypertensive disorder in pregnancy, including 1411 (0.6%) with chronic hypertension, 10 379 (4.2%) with pre-eclampsia, 731 (0.3%) with chronic hypertension with superimposed pre-eclampsia, and 10 864 (4.3%) with gestational hypertension. Women with, and infants exposed to, hypertension were more likely to suffer death or major morbidity than those without hypertension. Infants of mothers with hypertension were more likely to be to born preterm and small for gestational age. Just over half the women with major morbidity or mortality delivered in hospitals with a high level of medical care. In contrast, most infants with major morbidity or mortality were delivered in hospitals with neonatal intensive care units. Conclusions: Hypertension is a common complication of pregnancy, and adverse outcomes are increased among hypertensive women and their babies. Clinicians appear to be better at identifying and seeking an appropriate level of care for pregnancies where the infant is at risk of a poor outcome than when the mother is at risk. More specific antenatal indicators of poor maternal outcome would help guide the referral of MJA 2005; 182: 332-335 hypertensive women to higher levels of care.

Population-based trends in pregnancy hypertension and pre-eclampsia: an international comparative study

“…A significant part of the variation in baseline rates was likely related to differences in study population inclusion criteria and data-recording methods. Although the lower gestational age boundary varied by country (gestational age 20–22 weeks or birth weight 350–500 g for live births and 20–28 weeks for stillbirths), the impact was likely to be small as pregnancy hypertension and pre-eclampsia most frequently occur in the third trimester 7 27 40. Stillbirth, a complication of pre-eclampsia, is counted only from 28 weeks onwards in the Swedish data which may have reduced the country's rates.…”

“…Variability in the age, parity, chronic disease, smoking and multiple birth distributions will also influence the baseline rates of pregnancy hypertension and pre-eclampsia 2 7 12. Although data from Australia, the USA and Canada were from regional populations, these populations are likely to be more homogenous than the entire country populations and may be more similar to the European populations.…”

“…Increasing rates of early elective delivery before 40 weeks gestation have been reported internationally 20 22 23. Almost 90% of pregnancy hypertension and over 70% of pre-eclampsia events occur at term, but fewer pregnancies are reaching 40 weeks or beyond 7 27 40. Increasing rates of planned delivery of women with gestational hypertension could also explain why more study areas had decreases in pre-eclampsia rates 21.…”

“…Pre-eclampsia may be superimposed on pre-existing chronic hypertension. Although pre-eclampsia represents the severe end of the spectrum, women with any form of pregnancy hypertension are at increased risk of adverse outcomes 6 7…”

“…Population rates of pregnancy hypertension (based on routinely collected data) vary substantially in high-income countries, ranging from 4% to 10%, including pre-eclampsia rates of 2% to 5% 7 11 24–28. At least part of this variation is likely due to underascertainment and/or misclassification of gestational hypertension and pre-eclampsia 29…”