Progesterone is a hormone that helps the uterus grow during pregnancy and keeps it from contracting.
Treatment with progesterone during pregnancy may help some people reduce their risk for premature birth.
If you have a short cervix, treatment with vaginal progesterone gel may help prevent premature birth.
If you had a spontaneous premature birth in the past and were pregnant with just one baby, 17P shots may help prevent another premature birth.
Talk with your health care provider to about whether progesterone treatment is right for you.
What is progesterone?
Progesterone is a hormone. Hormones are chemicals made by the body.
Progesterone helps the uterus (womb) grow during pregnancy and keeps it from having contractions. If you have contractions in early pregnancy, it may lead to miscarriage. This is the loss of a pregnancy before 20 weeks of pregnancy. In later pregnancy, progesterone helps your breasts get ready to make breast milk. It also helps your lungs work harder to give oxygen to your growing baby.
Treatment with progesterone during pregnancy may help reduce the risk for premature birth among certain people. Premature birth is birth that happens too soon, before 37 weeks of pregnancy. Premature babies may need to stay in the hospital longer or may have more health problems that babies born full term. Full term means your baby is born between 37 weeks and 40 weeks of pregnancy.
There are two kinds of progesterone treatment:
Vaginal progesterone may help reduce your risk for premature birth if you have a short cervix and are pregnant with just one baby.
Progesterone shots may help reduce your risk for premature birth if you’re pregnant with just one baby and if you’ve had a baby that was born early in the past.
If you’re pregnant with more than one baby (twins, triplets or more), progesterone treatment isn’t for you.
Talk with your health care provider to find out whether progesterone treatment is right for you.
What is short cervix?
The cervix is the part of your uterus that opens and shortens during labor. These changes allow your cervix to become thinner and softer so your baby can pass through the birth canal during childbirth.
Your cervix is short if it's less than 2 centimeters (20 millimeters) long. If you have a short cervix, it may open too early, before you baby is ready to be born. When your cervix opens too early, it’s known as cervical insufficiency or incompetent cervix. If you have a short cervix, you have a 1-in-2 chance (50 percent) of having a premature birth.
Your health care provider may find that you have a short cervix during an ultrasound. Ask your provider about having an ultrasound to check for short cervix.
What is vaginal progesterone?
Vaginal progesterone may help prevent premature birth, but only if both of these describe you:
- You have a short cervix.
- You’re pregnant with just one baby.
If both of these describe you, your provider may give you a prescription for vaginal progesterone. It comes as a gel, a suppository or a capsule. You use an applicator that looks like a tampon to put the progesterone in your vagina every day. You may begin treatment before or up to 24 weeks of pregnancy, and continue it until just before 37 weeks. Vaginal progesterone can cause mild skin irritation. Research has not shown that vaginal progesterone causes serious side effects for you or your baby.
Research suggests that vaginal progesterone is not helpful in delaying pregnancy for people who:
- Are pregnant with more than one baby
- Have preterm premature rupture of membranes
- Have a positive fetal fibronectin test
- Had an episode of preterm labor that was stopped successfully
What are progesterone shots?
Progesterone shots are a kind of progesterone called 17 alpha-hydroxyprogesterone caproate (also called 17P, or Makena). The shots may be given to pregnant people who:
- Had a previous spontaneous premature birth when pregnant with just one baby. Spontaneous means that labor began on its own, without drugs or other methods. Or the sac around the baby broke early, causing labor.
- Are pregnant with just one baby.
- Don’t have liver disease, untreated high blood pressure, or a type of cancer that is sensitive to hormones.
If these describe you, your provider may prescribe progesterone shots. You begin the shots between 16 and 24 weeks of pregnancy, and you get a shot each week until 37 weeks.
Your health insurance or state Medicaid program may help pay for the shots. In some states, you may be able to get a kind of 17P from special pharmacies.
Even if you get progesterone shots, they don’t always work to prevent another premature birth. They don’t reduce your chances of giving birth early if you’re pregnant with more than one baby. And they don’t reduce your chances of giving birth early if your previous premature birth wasn’t spontaneous.
Talk with your provider about safety and side effects of progesterone shots. You may have some discomfort where the shot was given. 17P is safe for your baby.
Last reviewed: December 2020