Intensity of BP control during pregnancy does not affect rate of adverse outcomes
Less-tight versus tight control of hypertension in pregnancy.
Magee LA, von Dadelszen P, Rey E, et al.
N Engl J Med. 2015 Jan 29;372(5):407-17. doi: 10.1056/NEJMoa1404595
BackgroundHypertension is seen in almost 10% of pregnant women, either as pre-existing hypertension (1%), gestational hypertension without proteinuria (5-6%) or preeclampsia (2%) . Both pre-existing hypertension and gestational hypertension before week 34 are associated with a higher risk of perinatal and maternal complications [2-4].
Limited high-quality evidence is available on the use of tight blood pressure (BP) control during pregnancy. Guidelines for nonsevere hypertension during pregnancy recommend blood pressure targets that are consistent with either less-tight control or tight control.
The Control of Hypertension in Pregnancy Study (CHIPS) was designed to evaluate less-tight control versus tight control of nonproteinuric, nonsevere hypertension during pregnancy, with regard to perinatal and maternal outcomes. CHIPS was an open, multicentre, international, randomised, controlled trial, in which 519 women were assigned to less-tight-control and 511 to tight control of diastolic BP. The primary outcome was a composite of pregnancy loss or high-level neonatal care for more than 48 hours until 28 days of life or until discharge home, whichever was later. Serious maternal complications occurring up to 6 weeks post partum or until hospital discharge, was the secondary endpoint.
- BP was higher in women in the less-tight-control group than in those assigned to tight BP control (mean difference: 5.8 mmHg systolic (95%CI: 4.5-7.0) and 4.6 mmHg diastolic (95%CI: 3.7-5.4).
- The frequency of the primary outcome was not significantly different between the two levels of BP control (155 events, 31.4% with less-tight control, and 150 events, 30.7% with tight control, adjOR: 1.02, 95%CI: 0.77-1.35).
- No significant between-group differences were seen for other perinatal outcomes, including the frequency of respiratory complications and the number of newborns small for gestational age.
- The secondary endpoint was also similarly frequent in both groups (18 events, 3.7% with less-tight control vs. 10 events, 2.0% with tight control, adjOR: 1.74, 95%CI: 0.79-3.84).
- Severe hypertension was more often seen among women in the less-tight-control group (200, 40.6%) than among those in the tight control group (134, 27.5%), although the distribution of observed systolic and diastolic BP values was similar between the groups.
- Similar results were seen for the primary and secondary endpoints irrespective of the type of hypertension, whether antihypertensive therapy was used at the time of randomisation, whether the mother had gestational diabetes, the perinatal mortality ratio of the country and whether there was clinically reasonable adherence to the management algorithm.
ConclusionThis randomised trial shows that the risk of adverse perinatal outcomes or serious maternal complications does not differ between tight or less-tight control of maternal hypertension. A higher rate of severe maternal hypertension was seen in women in the less-tight control group.
Editorial comment “There is consensus that treatment of hypertension in pregnancy is warranted if blood pressure is sufficiently high to pose a risk of stroke (i.e., ≥160 mm Hg systolic or either ≥105 mm Hg diastolic or ≥110 mm Hg diastolic) or if there is associated renal or cardiovascular disease. In the absence of those indications, there is considerable debate about the need for treatment of mild hypertension (i.e., hypertension below these thresholds) during pregnancy. (…)
Although larger than previous trials, this study was similarly not powered to detect differences in frequencies of foetal or maternal deaths. These events were uncommon; perinatal mortality was 2.8% in the less-tight-control group and 2.3% in the tight-control group, and there were no maternal deaths. Although severe hypertension was more likely in the less-tight-control group than in the tight control group, the difference was not accompanied by an increase in the serious complications of hypertension or transient ischemic attack or stroke. Pulmonary edema, renal failure, and placental abruptions were uncommon, and their frequencies, along with the frequency of emergency department visits or hospitalizations (other than for delivery), did not differ materially between groups.(…)
The present report does not address whether outcomes vary according to the antihypertensive medication used. In summary, the current study showed that tight control of hypertension conferred no apparent benefits to the foetus and only a moderate benefit (a lower rate of progression to severe hypertension) for the mother. It does, however, provide valuable reassurance that tight control, as targeted in this study, does not carry major risks for the foetus or newborn.“
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