The SNAP-HT Trial: self-management of antihypertensive medication postpartum - can women do it better?
New onset hypertension affects one in ten women during pregnancy. Women may require large doses of antihypertensive medication postpartum, but the majority will be treatment-free by three to six months. Rapidly changing BP during this time poses a challenge in terms of appropriate antihypertensive dose adjustment postpartum and may be related to future cardiovascular risk. In essential hypertension, self-management significantly improved blood pressure (BP). We developed a novel postpartum self-management intervention, and performed an initial evaluation in a feasibility study.
Postnatal women, with gestational hypertension or pre-eclampsia requiring antihypertensive treatment, were randomised to self-management or usual care. Self-management involved daily home BP monitoring, using a validated device, and submission of readings via a mobile phone-based telemonitoring system, which provided automatic feedback and included an individualised medication reduction schedule. Women attended five follow-up visits over six months; at each visit BP was measured, using a validated, automated monitor. The primary outcome was feasibility. For analysis of differences in BP at follow-up, a repeated measures mixed-effects regression model was used.
91/188 (48%) women approached were randomised (45 intervention, 46 control). There were 9/91 (10%) withdrawals. Amongst the 82 complete cases, 403/410 (98%) follow-up visits were completed.
The groups had similar baseline characteristics. Their mean age was 32y (SD 5), mean body mass index 29kg/m2 (SD 8), and mean baseline BP (day 1-6 postpartum) 133/86mmHg (SD 14/10 respectively).
In the intervention group, 1075/1513 (71%) expected daily readings (on treatment) were submitted. BP measures at follow-up tended to be lower in the intervention group (table). This was most marked at 6 weeks [adjusted mean differences, self-management lower: systolic BP: -5.2 (-9.3 - -1.2); diastolic BP -5.8 mmHg (-9.1 - -2.5)] and the difference in diastolic readings persisted to six months [-4.5 mmHg (-8.1 - -0.8)].
The SNAP-HT study provides the first randomised controlled evaluation of BP self-management postpartum. Recruitment and retention rates suggest expanding the study would be practicable.The secondary outcome measures indicate that self-management might result in better postnatal BP control, and support evaluation in a large-scale multi-centre randomised controlled trial.