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Why Is Progesterone Used for Fertility Treatment?
In my fertility practice, I often have many questions about progesterone and why it must be used during in vitro fertilization (IVF), whether it is safe and what are its side effects. There is often confusion because the Food and Drug Administration (FDA) does not differentiate between natural progesterone and synthetic progesterone (progestins) in its warnings. While the FDA lumps natural progesterone with progestins in its warnings, there have not been any reliable studies that found the use of natural progesterone causes any risk to a developing fetus.
What Is Progesterone?
Progesterone is a naturally occurring hormone in the body. In women, the hormone is produced in the ovaries, the adrenal glands and in the placenta during pregnancy, and it is stored in the fat tissue. Progesterone is involved in a woman's menstrual cycle and supports pregnancy.
In women trying to conceive, progesterone supplements may be used to regulate periods for those who have stopped menstruating. If a woman is undergoing ovulation induction or IVF progesterone supplements are also used.
Why Are Progesterone Supplements Used for IVF?
The egg retrieval process during IVF typically removes the cells that would normally create progesterone after ovulation. The progesterone supplements are needed to thicken the uterine lining and prepare the body to support the embryo, so the embryo will successfully implant and grow.
Natural progesterone is used as a supplement for patients actively trying to conceive. This is what I use in my practice, and it is the type of progesterone most commonly used among fertility doctors throughout the United States.
The Food and Drug Administration (FDA) does not approve the use of synthetic progesterone (progestin) — such as birth control pills — during pregnancy. Progestins are mostly used to suppress ovulation, and in older studies they have been linked to a slightly increased risk of certain birth defects if used during pregnancy. Natural progesterone, however, is safe.
What Are the Different Types of Progesterone Prescribed?
During fertility treatment, a woman may be prescribed:
- progesterone in oil, which is an intramuscular injection
- vaginal gel, such as Crinone or Prochieve
- vaginal tablets such as Endometrin
- oral tablets such as Prometrium, which is also prescribed to use vaginally
- progesterone suppositories made to order by a pharmacist
For many years, Intramuscular injections were preferred by many fertility doctors because studies showed that pregnancy rates were higher. This is changing. More recent studies have shown that vaginal progesterone produced a lower rate of miscarriage and a similar live birth rate as intramuscular progesterone.
For most of my patients undergoing IVF, I use vaginal progesterone because it is less painful than intramuscular progesterone shots. For frozen embryo cycles or donor egg, we use a combination of vaginal progesterone with intermittent intramuscular progesterone, since the women don’t produce any progesterone themselves.
Side Effects of Progesterone
There are some common side effects when using progesterone, including:
- breast tenderness
- joint pain
- fluid retention/bloating
- hot flashes
- urinary problems
- abdominal pain or cramping
- vaginal discharge
If any of these become too uncomfortable or you are experiencing other side effects, call your doctor.