The Chronic Hypertension and Adverse Pregnancy Study (CHAP) study with over 2000 participants published last year in NEJM had concluded that keeping BP below 140/90 mm Hg in pregnant women with mild chronic hypertension was associated with better maternal and fetal outcomes.¹ Following publication of this study, BP below 140/90 mm Hg was adopted as the threshold when managing mild chronic hypertension during pregnancy.

A secondary analysis of the multicenter, randomized-controlled CHAP study was conducted with 434 subjects to investigate if tighter control of BP to less than 130/80 mm Hg (versus 130-139/80-89) would still be beneficial among pregnant women with hypertension and diabetes.² Besides mild chronic hypertension, women with pregestational diabetes or gestational diabetes (GDM) diagnosed at less than 20 weeks were included in this secondary analysis. Out of the 434 included in the trial, 217 patients had BP < 130/80 (average) and an equal number had BP ranging from 130-139/80-89 (average).

Findings presented at the 42nd Annual Pregnancy Meeting of the Society for Maternal-Fetal Medicine (SMFM) meeting showed that the risk of adverse events declined by 57% when BP was maintained below 130/80 mmHg and by 51.6% when the BP was 130-139/80-89 mmHg. Women in the lower BP group had higher odds of newly diagnosed chronic hypertension or GDM. They were also more likely to be on medications at the start of pregnancy

The incidence of preeclampsia with severe features, placental abruption or indicated preterm birth < 35 weeks was the primary composite outcome of the study. The incidence of preeclampsia with severe features was 19.4% in the lower BP group vs 43.8% in the higher BP group. Women in the higher BP group had higher preterm (before 35 weeks of gestation) deliveries; 23% vs 8.3%, respectively. Placental abruption occurred in less than one percent women in the lower BP group vs ~3% in the higher BP group.

Infants born to mothers in the lower BP ( group (below 130/80 mmHg) required fewer days of intensive care (14.7 vs 26.1 days, respectively) and they had better birth weight (3.2 kg vs 2.8 kg, respectively). Fetal or neonatal death was also lower (<1% vs 3.2%, respectively). The risk for small-for-gestational age (SGA), a secondary outcome of the study, did not increase in the group with lower BP.

These findings show that a target BP less than 130/80 was feasible in pregnant women with diabetes and mild chronic hypertension and was associated with better pregnancy outcomes.

References

1. Tita AT, et al. Treatment for mild chronic hypertension during pregnancy. N Engl J Med. 2022 May 12;386(19):1781-1792.
2. Harper LM. Abstract 18. Blood pressure control in patients with chronic hypertension and diabetes: should <130/80 be the target? Am J Obstet Gynecol. 2023;228 (1 Suppl); S16-S17. DOI: https://doi.org/10.1016/j.ajog.2022.11.023