Hypertensive disorders of pregnancy affect a significant number of pregnancies in the United States (prepregnancy or chronic hypertension [2.2%], gestational hypertension, including pregnancy-induced hypertension and preeclampsia [7.8%], and eclampsia [0.28%], and are increasing (Bruno et al., 2022; Martin et al., 2021). They influence birth outcomes for pregnant women and their infants and are associated with an increased risk of death due to cardiovascular causes later in life (Wang et al., 2021). Health care providers have previously used medications to lower blood pressures (BP) of greater than 160/110, but research was needed to determine if a lower threshold resulted in pregnancies with fewer complications (Sutton et al., 2018).

An open-label randomized controlled trial, the Chronic Hypertension in Pregnancy (CHAP) Trial was conducted in which women with a singleton pregnancy and mild chronic hypertension were assigned to one of two arms: 1) treatment with medication at a threshold of BP of 140/90 or 2) control, no treatment until BP reached a systolic BP of >=160 or a diastolic BP of >=105 (Tita et al., 2022). Over 2,400 patients were enrolled in 61 sites in this multicenter study, with approximately 1,200 women in each arm. Participants were 48% Black women, 28% non-Hispanic White women, and 20% Hispanic women. Both arms were similarly racially diverse. Most patients in the treatment arm received either labetalol or nifedipine (97.3%).

Primary outcome was a composite of preeclampsia with severe features, induced preterm birth at <35 weeks, placental abruption, and fetal or neonatal death. Other outcomes included risk of small-for-gestational age (SGA) infants, preterm birth, preeclampsia, and serious neonatal or maternal morbidity (Tita et al., 2022). Prevention of the primary outcome was significant in the treatment group, with an adjusted risk ratio of 0.82 (95% confidence interval 0.74-0.92, p < 0.001). There was no difference in rate of SGA infants (P = 0.76). The number of patients who would be needed to treat for this intervention was 14.7 to prevent one primary outcome event (Tita et al., 2022). In the context of mild chronic hypertension, an overall benefit was seen when BP of 140/90 is considered a treatable value, rather than reserving treatment until BP is 160/110. Although there was no difference in the risk for SGA infants, there were improvements in maternal morbidity.

Following publication of the CHAP trial, the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine issued a joint practice advisory recommending use of 140/90 as a treatment point for antihypertensives (American College of Obstetricians and Gynecologists & Society for Maternal-Fetal Medicine, 2022). The advisory did not include a treatment target or goal BP. Nurses should expect nurse midwives, nurse practitioners, and physicians to use these new guidelines when making decisions for the management of mildly hypertensive pregnant patients and should be prepared to educate patients on the importance of antihypertensive medications in managing this chronic condition.

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