According to a review of available studies in Obstetrics & Gynecology, “Although not all studies have shown a benefit, there is increasing evidence to suggest that progesterone supplementation from 16 to 20 weeks of gestation through 34 to 36 weeks of gestation may prevent preterm birth (PTB) in some women at high risk by virtue of a prior spontaneous preterm birth or cervical shortening.”
As with all treatments, educate yourself about the options and discuss with your doctor which is best for your situation.
The same article in Obstetrics & Gynecology detailed some interesting findings with regard to progesterone suppositories:
In a randomized clinical trial, the daily use of progesterone by vaginal suppository in high risk women between 24 and 34 weeks of gestation significantly reduced preterm uterine contractions and the risk of delivery before 37 weeks. In a different study, women also had a lower rate of spontaneous PTB prior to 34 weeks while using progesterone suppositories, compared with those who received placebo. This study concluded progesterone suppositories can reduce the frequency of uterine contractions and the rate of preterm delivery in women who are at risk of prematurity.
Intramuscular Injections of Progesterone
Again referring to the Obstetrics & Gynecology article, there have been significant findings with regard to progesterone injections (also called 17P):
In a randomized clinical trial, once weekly intramuscular injections of 17P from 16 to 20 weeks of gestation through 36 weeks of gestation significantly reduced the risk of spontaneous PTB prior to 37 weeks.
Progesterone and Multiples
Several recent studies have found the use of progesterone in twin pregnancies to be “ineffective” at preventing preterm birth. The Obstetrics & Gynecology article goes on to say, “Whether this is due to inadequate dosing of progesterone in these studies as has been suggested by some investigators or whether it speaks to a different mechanism of PTB in twins as compared with singletons is not known.”