Progesterone is an important part of infertility treatment, with fertility specialists often prescribing progesterone supplements to help improve pregnancy rates from IVF. So why is progesterone supplementation used and can it help with natural conception rates as well? Firstly, it helps to understand the role of progesterone in pregnancy.

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). One of the most important functions of progesterone is to prepare the lining of the uterus (endometrium) to allow a fertilised egg (embryo) to implant. If a pregnancy does not take place, progesterone levels will fall and you will have your period. If an embryo implants into the lining of the uterus, the resulting conception will produce the hormone Human chorionic gonadotropin (hCG) which in turn will direct the ovaries to produce progesterone until eight weeks into the pregnancy. After that time, progesterone will be produced by the placenta throughout the remainder of the pregnancy.

Do I need progesterone if I am trying for natural conception?

There is no evidence to suggest that giving progesterone supplements to otherwise healthy women in early pregnancy has any additional benefits or reduces the risk of spontaneous miscarriage. A recent randomized trial also found no benefit from progesterone supplements in a group of women with repeated miscarriage. However, despite this, there may still be some benefit from this approach in individual cases and you should discuss it with your doctor in the light of your own particular circumstance.

When and how should I take progesterone?

Fertility specialists usually prescribe progesterone supplementation to start a few days after the eggs are collected. Progesterone supplements generally come in the form of a vaginal suppository or intramuscular injection. Current research is focussed on improving the effectiveness of oral preparations of progesterone, as past studies have found that only 10% of progesterone is absorbed when taken orally. While both the suppository and injection methods appear to be equally effective, vaginal preparations are preferred by most patients and fertility specialists alike. Alternatively, luteal phase support with intermittent or several hCG injections can be used to stimulate the ovaries to produce progesterone. This is not advisable if more than ten follicles are found on ultrasound, as this may cause an ovarian cyst or ovarian hyperstimulation (OHSS).

What are the risks of taking progesterone?

Many studies have been performed to look at the use of natural progesterone during IVF treatment. These studies have shown that progesterone will pose no significant risk to you or your baby. Although, for some women, vaginal preparations can cause discharge and local irritation.

What is next?

If you have any questions about taking progesterone and the options available, please to our board-certified reproductive endocrinologist.