Moms, Newborns Do Just Fine, Thanks, After 'Tight' BP Control in Pregnancy

Marlene Busko

February 02, 2015

BOSTON, MA — There were no significant differences in pregnancy loss, need for high-level neonatal care, or overall maternal complications in women with mild to moderate hypertension at 14 to 33 weeks' gestation randomized to tight vs "less tight" blood pressure (BP) control in an international trial with nearly a thousand patients[1]. However, women assigned to tight BP control as opposed to less tight control were significantly less likely to develop severe hypertension.

Tight and less tight control in the Control of Hypertension in Pregnancy Study (CHIPS), published in the January 29, 2015 issue of the New England Journal of Medicine, were defined as meeting diastolic BP treatment targets of 85 and 100 mm Hg, respectively.

CHIPS is substantially larger than any previous trial looking at the treatment of nonsevere hypertension in pregnancy, which remains controversial, observe Dr Laura A Magee (British Columbia Woman's Hospital and Health Centre, Vancouver) and colleagues. Meta-analyses and other, usually small, randomized studies have variously shown risks or benefits from tight vs less tight BP control in pregnancy, they write, but the current study doesn't greatly support either kind of difference between approaches.

"The current study showed that tight control of hypertension conferred no apparent benefits to the fetus and only a moderate benefit . . . for the mother. It does, however, provide valuable reassurance that tight control, as targeted in this study, does not carry major risks for the fetus or newborn," according to Drs Caren G Solomon and Michael F Greene (Massachusetts General Hospital, Boston) in an accompanying editorial[2].

CHIPS enrolled women at 14 weeks'' to 33 weeks, 6 days gestation with nonsevere hypertension at 95 sites in 16 countries from 2009 to 2012. Of the 987 randomized to less tight or tight BP control, 74.6% had preexisting hypertension and the rest had gestational hypertension. The women participated in the study an average of 12.1 weeks prior to delivery.

The composite primary outcome of pregnancy loss or high-level neonatal care for more than 48 hours during the first 28 postnatal days was similar in the women assigned to less tight or tight BP control at 31.4% and 30.7%, respectively. The adjusted odds ratio (OR) was 1.02 (95% CI 0.77–1.35).

There were no significant between-group differences in the proportion of newborns that were small for their gestational age or frequency of neonatal respiratory complications.

Serious maternal complications (including transient ischemic attack or stroke, pulmonary edema, renal failure, and transfusions) occurred in 3.7% and 2.0% of women with less tight vs tight BP control, respectively (OR 1.74; 95% CI 0.7–3.84).

Almost all serious complications were transfusions. About half of women in both groups developed preeclampsia. None died in pregnancy.

More women in the less tight (40.6%) than the tight-control group (27.5%) experienced severe hypertension (defined as BP >160/110 mm Hg) (P<0.001). Pulmonary edema, renal failure, and placental abruptions were uncommon and occurred at similar rates in both groups.

Two-thirds of women who received antihypertensive therapy were treated with labetalol, which had been designated the agent of first choice. Those with tight control achieved a diastolic BP that averaged 4.6 mm Hg lower than those with less tight control.

"Head-to-head trials of antihypertensive agents commonly used in pregnancy (labetalol, methyldopa, and nifedipine) have not shown significant differences in major fetal or maternal outcomes, but some—albeit inconsistent—evidence has suggested a reduced risk of severe hypertension and of an associated need for hospitalization in association with the use of labetalol vs methyldopa," issues that were not explored in the trial, observe Solomon and Greene.

The study was supported by a grant from the Canadian Institutes of Health Research. Magee had no relevant financial relationships; disclosures for the coauthors are listed in the article. Solomon is an deputy editor and Greene is an associate editor at the New England Journal of Medicine.

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