Objective: To determine whether 'less tight' (versus 'tight') control of nonsevere hypertension results in a difference in diastolic blood pressure (dBP) between groups.
Design: Randomised controlled trial (ISRCTN#57277508).
Setting: Seventeen obstetric centres in Canada, Australia, New Zealand, and UK.
Population: Inclusion: pregnant women, dBP 90-109 mmHg, pre-existing/gestational hypertension; live fetus(es); and 20-33(+6) weeks. Exclusion: systolic blood pressure > or = 170 mmHg and proteinuria, contraindication, or major fetal anomaly.
Methods: Randomisation to less tight (target dBP, 100 mmHg) or tight (target dBP, 85 mmHg) blood pressure control.
Main outcome measures: Primary: mean dBP at 28, 32 and 36 weeks. Secondary: clinician compliance and women's satisfaction. Other: serious perinatal and maternal complications.
Results: A total of 132 women were randomised to less tight (n = 66; seven had no study visit) or tight control (n= 66; one was lost to follow up; seven had no study visit). Mean dBP was significantly lower with tight control: -3.5 mmHg, 95% credible interval (-6.4, -0.6). Clinician compliance was 79% in both groups. Women were satisfied with their care. With less tight (versus tight) control, the rates of other treatments and outcomes were the following: post-randomisation antenatal antihypertensive medication use: 46 (69.7%) versus 58 (89.2%), severe hypertension: 38 (57.6%) versus 26 (40.0%), proteinuria: 16 (24.2%) versus 20 (30.8%), serious maternal complications: 3 (4.6%) versus 2 (3.1%), preterm birth: 24 (36.4%) versus 26 (40.0%), birthweight: 2675 +/- 858 versus 2501 +/- 855 g, neonatal intensive care unit (NICU) admission: 15 (22.7%) versus 22 (34.4%), and serious perinatal complications: 9 (13.6%) versus 14 (21.5%).
Conclusion: The CHIPS pilot trial confirms the feasibility and importance of a large definitive trial to determine the effects of less tight control on serious perinatal and maternal complications.