Progesterone and 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 randomised 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.

Why is progesterone prescribed during IVF treatment?

During an in vitro fertilisation (IVF) cycle, medications are usually used to prevent patients from releasing an egg early (premature ovulation). These medicines affect your progesterone levels. Therefore, your fertility specialist may prescribe a progesterone supplement to make up for this decrease in your ovary’s ability to make progesterone. That way, an embryo can implant and grow inside your uterus. Many scientific studies have looked at pregnancy rates in IVF cycles that used progesterone. These studies have shown that the rates are much higher compared to cycles where no progesterone was used.

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 hyper stimulation (OHSS).



For IVF patients, progesterone supplementation can be safely withdrawn at the time of a positive pregnancy (hCG) test, as the body regains its ability to secrete progesterone by this stage.

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 a discharge and local irritation.

What next?

If you have any questions about taking progesterone and the options available, please speak to your local fertility specialist. 



Find out more:Fertility Specialists in QLD, Fertility Specialists in NSW, Fertility Specialists in VIC, Fertility Specialists in TAS, Fertility Specialists in Singapore