What is progesterone?

Progesterone is a hormone produced by the ovary. It is first detected in the middle of the menstrual cycle when an egg is released (ovulation). Progesterone prepares the lining of the uterus (endometrium) for a fertilized egg (embryo) to stick or implant. If a pregnancy does not take place, progesterone levels drop and a woman has her period. If an embryo implants into the lining of the uterus, the ovary continues to produce progesterone for eight weeks to ten weeks. After that time, the placenta produces progesterone to support the pregnancy.

Why do doctors prescribe progesterone during fertility treatments?

During an in vitro fertilization (IVF) cycle, medications are usually used to prevent you from the early release of an egg from the ovary (premature ovulation). These medicines affect your ovary’s ability to make progesterone. Your doctor may prescribe a progesterone supplement to make up for this decrease in your progesterone levels. Progesterone support the uterine lining and helps an embryo implant and grow inside. Many scientific studies have looked at pregnancy rates in IVF cycles that used progesterone. These studies have shown that pregnancy rates are much higher in cycles with supplementation compared with those without.

When and how should I take progesterone?

Progesterone supplementation is usually started on the day of egg retrieval. If a pregnancy takes place, supplementation may continue throughout the first trimester. Progesterone may be taken as an intramuscular injection or given through the vagina as a suppository, gel, or tablet. There appears to be no difference in the chance of becoming pregnant or continuing a pregnancy based on how the progesterone is given. It is important to follow instructions and talk with your doctor about the form of progesterone that best fits your needs. Taking progesterone as a pill does not work well to support the pregnancy because it is not absorbed by the stomach enough to help the pregnancy.

What are the risks of taking progesterone?

There are two basic types of progesterone. One is a synthetic type called medroxy-progesterone acetate. The other type more closely resembles the natural progesterone produced by the ovaries. The natural form is the one recommended for use in pregnancy.