She also noted that nearly a quarter of patients had a history of depression, and one in five had a history of migraine. More than half of patients overall had at least one previous or ongoing chronic medical condition.
A small number of patients in each group were excluded for protocol violations, pregnancy termination, intrauterine fetal demise, or loss to follow-up. The final intent-to-treat population included 238 in the metformin group and 240 who received placebo.
The per-protocol analysis was conducted two ways: In the first analysis, only those who dropped out were excluded, leaving 209 in the metformin group and 223 in the placebo group. The second analysis included those whose adherence to taking the study medication was assessed at 90% or better. For this second per-protocol analysis, just 142 metformin takers and 156 in the placebo group remained.
In the intent-to-treat population, the primary endpoint – a composite outcome of late miscarriage and preterm delivery – yielded an odds ratio of 1.99 favoring metformin over placebo, a figure that fell short of statistical significance (95% confidence interval, 0.93-4.51; P = .08).