Adverse Pregnancy Outcomes and Chronic Hypertension

Pregnant women with chronic hypertension have an increased risk of preeclampsia, cesarean section, and preterm delivery, researchers noted in a meta-analysis of 55 studies. 

Pertinent Points

- Pregnant women with chronic hypertension are at increased risk for having babies delivered preterm, infants with low
birth weight, and experience neonatal death, a meta-analysis of 55 studies revealed.

- The relative risk of preeclampsia in women with chronic hypertension was on average nearly eight times higher than preeclampsia in nonhypertensive women.

- Babies born to women with chronic hypertension were at least twice as likely to have adverse neonatal outcomes, compared with the general population.

The findings of adverse outcomes also point to a need for a consistent trial design to study women with chronic hypertension, the authors suggested. They also emphasized the importance of increased surveillance for women with chronic hypertension and suggested the use of pre-pregnancy counseling. Finally, the researchers concluded that more work is needed to develop strategies for predicting women at greatest risk, determining optimal drug treatments, and reducing adverse pregnancy outcomes.

Researchers from King's College London reported in BMJ that after combining data from 55 studies performed in 25 countries, high blood pressure in pregnant women increases the risk of preterm delivery, low birth weight, and neonatal death. The combined data included information from nearly 800,000 pregnancies.

The relative risk of preeclampsia in women with chronic hypertension was on average nearly eight times higher than preeclampsia in non-hypertensive women, the authors reported. In addition, babies born to women with chronic hypertension were at least twice as likely to have adverse neonatal outcomes, compared with the general population, the authors noted.

Among the results reported, the researchers found women with chronic hypertension had high pooled incidences of:

- Superimposed preeclampsia (25.9%, 95% confidence interval, 21.0% to 31.5%).
- Cesarean section (41.4%, 35.5% to 47.7%).
- Preterm delivery at less than 37 weeks’ gestation (28.1%, 22.6% to 34.4%).
- Babies with a low birth weight of less than 2500 g (16.9%, 13.1% to 21.5%).
- Neonatal unit admission (20.5%, 15.7% to 26.4%).
- Perinatal death (4.0%, 2.9% to 5.4%).

In an accompanying editorial, Drs. Tine Clausen and Thomas Bergholt from the University of Copenhagen emphasized that more research is needed to understand the role of pre-gestational hypertension and to develop better clinical management standards. 

“An urgent need remains for research to establish best clinical practice for antenatal care, antihypertensive treatment, and timing of labour in women with uncomplicated chronic hypertension during pregnancy,” they wrote.