Progesterone and assisted reproduction

Progesterone and assisted reproduction go hand in hand.. In assisted reproduction treatments, it is generally necessary to administer an extra supplement of progesterone, especially in in vitro fertilisation treatments. After the extraction of the oocytes, there may be a decrease in the natural production of this hormone, which is vital and necessary for implantation and the proper development of the pregnancy. This highlights the important relationship between progesterone and assisted reproduction.

Why is progesterone important for pregnancy?

There are three main phases in the menstrual cycle:

1. Menstruation (resulting from the shedding of the endometrium).
2. The follicular phase (in which the dominant ovarian follicle produces the oestrogens necessary for the development of the endometrium).
3. The luteal phase, which follows an intermediate ovulatory phase.

After ovulation, the secretory stage or luteal phase begins, which is characterised by the production of progesterone (by the corpus luteum of the ovary) and, to a lesser extent, oestrogen. Progesterone causes the endometrium to mature, which has previously grown due to the stimulation of oestrogen in the uterus.

Progesterone production must occur at the right time and in sufficient quantities to produce the necessary changes in the endometrium and allow for proper embryo implantation. In this context, progesterone and assisted reproduction are inseparable, as even small hormonal imbalances can interfere with endometrial receptivity and reduce the likelihood of a successful pregnancy.

Progesterone and assisted reproduction: Why is hormone administration necessary in in vitro fertilisation treatment?

In in vitro fertilisation with own eggs or egg donation, medications such as GnRH analogues and antagonists are used to improve the efficiency of the treatment, but these can alter the development and maturation of the endometrium due to inadequate production of progesterone by the ovary (corpus luteum).

To avoid this, a progesterone supplement is indicated after ovarian puncture or after egg donation.

Progesterone dosage before embryo transfer

Progesterone can be administered vaginally, orally or subcutaneously.

The most commonly used route is vaginal. In in vitro fertilisation cycles with fresh embryo transfer, the usual doses are between 400 and 600 mg per day. Because every woman responds differently, progesterone and assisted reproduction protocols must be carefully adapted, with personalised monitoring to ensure each patient receives the most effective dosage.

In oocyte donation or frozen embryo transfer cycles, where preparation often involves a hormone replacement or medication cycle, the doses generally used are 80 0 mg per day.

What are normal progesterone levels for embryo transfer?

In a hormone replacement cycle, blood progesterone levels are checked prior to embryo transfer. If the level is below 10 ng/mL, the dose of vaginal progesterone should be increased, injectable progesterone should be added, or the rectal route should be used to improve absorption of the medication, as a level below 10 mg/mL is associated with lower pregnancy rates and a higher risk of miscarriage. Several studies have confirmed the link between progesterone and assisted reproduction success rates, showing that optimised supplementation can improve implantation outcomes and reduce miscarriage risk.

How long is progesterone administration necessary?

Progesterone administration is necessary until the placenta is functional and begins to produce enough progesterone to support the development of the pregnancy. This occurs from the sixth week of gestation onwards.

In artificial insemination cycles or frozen embryo transfer in a natural cycle, progesterone supplementation is not strictly necessary, but it is generally recommended for safety reasons, and the doses used are lower.

Ultimately, progesterone and assisted reproduction are deeply connected, not only from a medical standpoint but also emotionally, since patients feel reassured knowing their treatment includes essential hormonal support to maximise their chances of pregnancy.

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