a Dosing regimens and duration not specified further.
bd = twice daily; CI = confidence interval; DB = double-blind; N = number; NMP = natural micronised progesterone; OB = observational; PTD = preterm delivery; qds = four times daily; RCT = randomised controlled trial; RET = retrospective; RR = relative risk; SD = standard deviation; sPTD = spontaneous PTD; tds = three times daily.
Table 4. Studies evaluating natural micronised progesterone sustained-release for high-risk pregnancy.