Progesterone (P17) Shots to Prevent Premature Labor

A baby is considered premature if he is born before 37 weeks. According to the March of Dimes, 1 in 8 births are considered premature or preterm. There are a few things that put a woman at higher risk of going into labor prematurely. These include a diagnosis of incompetent cervix, uterine abnormalities, placenta previa, polyhydramnios, and a history of preterm labor.

What can be done to prevent premature labor?

Up until recently, there weren’t many options for preventing premature labor. Women who went into early labor were generally given a type of drug called a tocolytic. Tocolytics slow down or stop labor contractions. Tocolytics, however, may only delay labor for a few days. A new medication called P17 (or hydroxyprogesterone caproate) may prevent premature labor for some women.

What is P17 and how does it work?

P17 or hydroxyprogesterone caproate is a synthetic form of the hormone progesterone. Although researchers are not entirely clear on how it works to prevent premature labor, progesterone is believed to be involved in the labor process. As labor begins, progesterone declines sharply. Supplementing a woman’s progesterone levels with P17 injections may allow her to stay pregnant longer. Progesterone is thought to help keep the uterus calmer. P17 injections may keep the uterus quieter and reduce the amount of premature labor contractions in women at risk. In addition, P17 may help women who have had PPROM (preterm premature rupture of membranes). Scientists have found that proteins in p17 help to strengthen the fetal membranes and may prevent PPROM.

Who should take P17?

In February 2011, P17 was approved by the FDA to reduce the risk of premature labor in women with a previous history of at least one preterm birth. It has not been approved for women with no prior history of premature labor or for women with other conditions such as multiple pregnancies.
Women with a history of premature labor can talk to their doctors about taking P17 injections. If you are a good candidate for P17, your doctor will begin giving you an injection weekly, starting sometime between 16 weeks and 20 weeks of pregnancy. P17 is injected intramuscularly (usually in your hip) at your doctor’s office. You will receive the progesterone injections until your 37 weeks pregnant and no longer at risk of giving birth prematurely.

Side Effects & Risks from P17

Studies on P17 have found that it is safe for mother and baby to use. Children of moms who used P17 during pregnancy were evaluated at age 2-5. Scientists found that the children whose moms used P17 during pregnancy were no different developmentally than children whose moms did not take P17.
Possible side effects from P17 include pain, swelling, itching, bruising, or a lump at the injection site. Rarer more serious side effects include blood clots, allergic reactions such as hives, itching, or swelling of the face, and yellowing of the skin and eyes.