Prevention of Preterm Birth Redux: Progesterone Works

Preterm birth (<37weeks gestation) occurs in approximately 12% of births in the United States and results in 26,000 infant deaths leading to our unenviable rank of 55th in the world for infant mortality [1,2]. Preterm birth is also extremely expensive with an economic cost (2007) of $26.2 billion accounting for approximately 50% of all pregnancy costs [3]. The diagnosis of preterm labor is controversial. Thus acute tocolytic management of uterine contractions once labor has started is difficult and, even if successful, such treatment is not continued long-term [4]. Complicating matters further is that many variables, such as race, age, socioeconomic standing, bleeding, genetics, etc., are not modifiable risk factors. All this has left obstetricians, as well as obstetric nurses/nurse mid-wives, in a difficult position in their attempt to reduce preterm births. However, we have one thing that has been shown to decrease early delivery 17Hydroxyprogesterone Caproate (17P). The use of 17P (250 mg injected weekly) in women with a singleton pregnancy who have had a prior spontaneous early delivery, revealed a diminution in preterm births in every study (Figure 1) [5]. All of these reports showed a reduction in preterm births (<37 weeks gestation) averaging 22%. Two of the studies also reported a reduction in deliveries below 32 weeks gestation while four of the investigations noted a significant reduction in the neonatal deaths by 42%. Likewise for the studies which reported birthweights among treated patients, they noted neonates were 214-512 g heavier than control off-spring. Progesterone appears to have its salutary effects by several mechanisms. First, progesterone decreases the number of myometrial oxytocin receptors and increases gap junctions. The drug also counteracts prostaglandin production by the amniochorion while enhancing the structural integrities of the cervix [6].