Preterm birth
Progesterone supplementation is one of the treatment options for
prevention of preterm birth. Meta-analyses have confirmed that
progesterone is effective at reducing the risk of preterm birth before
34 weeks and before 37 weeks in women with singleton pregnancies and a
history of a previous preterm birth, and at reducing the risk of preterm
birth before 34 weeks in women with a short
cervix.28.29 No significant differences were found
between natural progesterone (oral/vaginal) and IM
17OHP-C28 or between routes of administration (oral,
vaginal and IM).29
Studies evaluating oral NMP for prevention of preterm birth are
summarised in Table 3 . Three RCTs compared oral NMP with
placebo for prevention of preterm delivery (PTD) in women with a history
of previous spontaneous PTD. Two of these studies (n = 150, and n = 212)
found that oral NMP significantly reduced the rate of PTD and increased
the mean gestational age at delivery compared with
placebo.30,31 The third study (n = 33) found numerical
improvements in these parameters with oral NMP compared with placebo,
but the differences did not achieve statistical significance, probably
because the study was underpowered.32 A meta-analysis
of these same three studies demonstrated a significantly decreased risk
of preterm birth at <37 weeks gestation (relative risk
[RR] 0.68; 95% CI 0.55−0.84) and at <34 weeks gestation
(RR 0.55; 95% CI 0.43−0.71), and increased gestational age of delivery
(mean difference 1.71 weeks; 95% CI 1.11−2.30) with oral NMP compared
with placebo.33 A noncomparative observational study
(n = 345) also suggested that oral NMP may be effective at preventing
PTD.34 A small retrospective analysis comparing
different routes of administration of progesterone in women at high-risk
for preterm labour (n = 30) found a numerically lower rate of PTD with
vaginal progesterone than with oral NMP, but no statistical comparison
was performed.35
Studies investigating oral NMP as maintenance tocolysis are few
(Table 3 ). A small RCT from France reported no differences
between oral NMP and placebo in terms of pregnancy prolongation;
however, adjuvant oral NMP significantly reduced the requirement for
intravenous β-mimetic (ritrodrine) and shortened the mean hospital stay
by 4.2 days.36 A RCT from India in 90 women with
arrested preterm labour found that maintenance tocolysis with oral NMP
significantly prolonged the latency period (days gained until delivery)
and significantly reduced the number of preterm births compared with
placebo.37