Women with gestational hypertension are at risk of developing pre-eclampsia. It has been defined by the American College of Obstetricians and Gynecologists (ACOG) as blood pressure (BP) of ≥140/90 mmHg after 20 weeks of pregnancy, two readings taken in a gap of at least 4 hours in women with normal pre-pregnancy BP without proteinuria or severe features and the elevated BP returns to normal after childbirth. A systolic BP of 160 mmHg or diastolic BP of 110 mmHg is considered severe gestational hypertension.¹

A recent study has suggested that a BP of 130-139/80-89 mmHg during pregnancy is also associated with a high risk of developing preeclampsia. The findings of the study were presented at the 2023 Annual Pregnancy Meeting of the Society for Maternal-Fetal Medicine (SMFM) held in San Francisco, California and also simultaneously published in the American Journal of Obstetrics & Gynecology^.2

In this study, researchers set out to investigate if broadening the definition of gestational hypertension (GHTN) to include BP of 130-139/80-89 mmHg as Stage 1 GHTN was associated with risk of pre-eclampsia.

For this, the researchers retrospectively analysed data of pregnant women who delivered between October 2016 to March 2022. Those with chronic hypertension and high BP before 20 weeks were not included in the study group. Based on the baseline BP reading, 23,954 deliveries were categorized as normotensive, 12,841 were categorized as stage 1 GHTN with BP of 130-139/80-89 mmHg while 2,591 were in the Stage 2 GHTN category with BP ≥140/90 mmHg. Women with gestational hypertension were more likely to have obesity.

Women with stage 1 GHTN were four times likely to develop preeclampsia with severe features (4%), which was the primary study outcome, compared to women who were normotensive during pregnancy (1%) with adjusted odds ratio (aOR) of 4.28. The probability of cesarean births, a secondary outcome of the study, was also higher in this group with aOR of 1.19.

When the perinatal outcomes were compared according to the BP category, the odds of giving birth to a low birthweight infant was higher in the stage 1 GHTN group (4.4%) compared to the normotensive group (3.5%) with aOR of 1.26. However, other neonatal outcomes such as fetal growth retardation (2.8% vs 2.8%), stillbirths (0.3% vs 0.4%) and 5-minute APGAR score of <4 (0.8% vs 0.9%) were comparable between the two groups.

Expectedly, the odds of developing pre-eclampsia with severe features was significantly higher in women with stage 2 GHTN (15%) with aOR of 18.69 compared to the normotensive group and aOR of 4.37 compared to stage 1 GHTN group. The chances of adverse perinatal outcomes were also increased in women with stage 2 GHTN with low birth weight (10.5%) with aOR of 1.98 vs normotensive group and 1.91 vs stage 1 GHTN, fetal growth restriction (3.8%) with aOR of 1.28 vs normotensive group and 1.18 vs stage 1 GHTN, stillbirth (0.5%) with aOR of 0.86 vs normotensive group and 1.31 vs stage 1 GHTN and 5-minute APGAR score of <4 (1.0%) with aOR of 1.01 vs normotensive group and 1.29 vs stage 1 GHTN.

Hence, women found to be in stage 1 of gestational hypertension must be closely monitored during pregnancy to prevent the development of pre-eclampsia and other adverse maternal and fetal outcomes.

References

1. Gestational hypertension and preeclampsia: ACOG Practice Bulletin, Number 222. Obstet Gynecol. 2020 Jun;135(6): e237-e260. Available at: https://www.preeclampsia.org/frontend/assets/img/advocacy_resource/Gestational_Hypertension_and_Preeclampsia_ACOG_Practice_Bulletin,_Number_222_1605448006.pdf. Accessed on April 22, 2023.
2. Mussarat N, et al. Expanded classification of gestational hypertension as a marker for adverse outcomes. Am J Obstet Gynecol. 2023 Jan.;228 (1 Suppl): S18. DOI:https://doi.org/10.1016/j.ajog.2022.11.025.