Statistical analysis
We followed the intention-to-treat principle and included all randomized
participants. The target sample size for enrollment was 150 participants
to establish feasibility and given cost constraints, with 120 from the
primary site and 30 from the second site (as described above), for a
target of 50 in each of the three arms, following published guidelines
for feasibility studies.(26) A formal sample size calculation was not
performed as the primary objective of this study was to assess
feasibility. All analyses were performed in Stata IC 16 software package
(StataCorp LP, College Station, TX). Continuous variables are reported
as means with 95% CI or SD (or medians with interquartile ranges
[IQR]) and categorical variables are reported as count and
proportions. Differences between arms were reported with 95% confidence
intervals (95% CI). An interim analysis was performed following
completion of the study at the primary study site as was initially
outlined in the study protocol prior to adding the second study site. To
evaluate the effect of the interventions (HH4NM + HBPM vs. HBPM alone
vs. control), we compared continuous variables between the three arms at
the second study visit (follow-up) using standard ANOVA. We also
compared the change in outcomes of interest between arms using ANOVA. At
the same time points, categorical data were compared between arms using
logistic regression and χ2 test. In sub-group
analyses, we evaluated the feasibility and effects of the interventions
by race, pre-pregnancy BMI category, and type of hypertensive disorder
of pregnancy. We used all data available from randomized participants
without replacement of missing data.