Progesterone for the Prevention of Preterm Labor

What is Progesterone?

Progesterone is a naturally occurring hormone secreted by a structure in the ovary called the corpus luteum, shortly after ovulation. Progesterone causes the uterine lining to thicken and ready itself for implantation of the fertilized ovum and must be present in high levels for implantation to occur. Progesterone also decreases
contractility of the uterus and thus prevents uterine contractions from causing an early miscarriage. If fertilization does not occur, the corpus luteum degrades, progesterone levels fall, and the uterine lining is shed with menstruation. If pregnancy occurs, the corpus luteum continues to produce progesterone until the
placenta is able to take over this function.

What is 17P?

17 alpha-Hydroxyprogesterone Caproate (17P) is a progestin medication similar to the naturally occurring hormone progesterone. A recent study by The National Institutes of Health (NIH) has shown that in women with a history of preterm delivery, weekly injections of 17P reduced the risk of delivering before 32 weeks by
42% and reduced the preterm birth rate by 34%. Additionally, babies born to the women treated with 17P injections had a lower risk of several problems that may affect preterm infants.

Weekly injections generally begin between the 16th and 20th week of pregnancy and continue until the end of pregnancy. 17P has a relaxing effect on the uterine muscle and makes the uterus less able to contract.

What are the potential side effects of 17P?

The most common side effects include soreness, swelling, itching and bruising at the injection site. Less common side effects include headache, nervousness, dizziness, fatigue, depression, formation of blood clots, water retention, blurred vision, spotting or vaginal bleeding, jaundice, weight gain or loss, allergic rash with or without itching, acne, breast tenderness or enlargement, increased blood pressure and changes in sexual desire. Coughing, difficulty breathing, chest tightness and/ or allergic type reactions have occurred as well.

Rare but severe side effects include formation of blood clots in the legs or lungs and stroke.

There is evidence of potential adverse effects on the baby when this drug is used during the first four months
of pregnancy.

How can you help yourself at home?

If you have had a previous preterm delivery you may be told to do these things:

  • Increase your rest. Resting on your sides is a helpful way to keep your uterus relaxed.
  • Fluid intake. During your pregnancy, it is even more important to drink at least 6-8 glasses of fluid per day.
  • Bedrest. Your doctor or provider may ask you to take rest periods.
  • Decrease strenuous activity. Your provider may ask that you do not do any heavy physical activity.
  • Sexual activity. Your doctor may ask that you stop or limit your sexual activities.

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