There are three common indications for using medications to induce ovulation:
- Patients who do not ovulate spontaneously, for example patients with PCOS
- Women with suboptimal ovulation, such as those with short periods (less than 28 day cycles), long periods or infrequent ovulation, or those with low progesterone levels
- Multi-follicular development, which is the goal in women who have not been successful at conceiving with mono-follicular (natural) ovulation over several months
How Ovulation Induction Works.
FSH (Follicle Stimulating Hormone) is a hormone released by the pituitary in the brain. FSH stimulates follicular growth and development. FSH release from the brain can be induced by pills, such as Clomiphene (Clomid) and Femara (Letrazole), or it can be given directly by subcutaneous injection. When the ovary is quiet, the estrogen levels are low, and the ovarian follicles are small.
Both pills, Clomid and Letrazole, trick the brain into believing that the ovaries are not working and thus the pituitary releases more FSH, resulting in mono-follicular, or sometimes, multi-follicular development. These pills are usually taken for 5 days and this is generally enough to induce ovulation.
The subcutaneous injections contain FSH and directly stimulate follicular development. Injections bypass the natural checks and balances of the brain and thus the chance of multi-follicular development is higher. Multi-follicular development usually results in higher pregnancy rates, but also, not surprisingly, in a significantly higher chance of twins or multiples, which we considered a risk from these treatments.
Trigger Shots for Ovulation Induction
To coordinate the timing of insemination, induce the rupture of the follicle, and improve the levels of progesterone production (to support the early pregnancy), we generally use a trigger injection once the follicle has reached maturity. Maturity is determined by follicular size on ultrasound or a natural LH surge.
The egg is usually released 28 to 42 hours after the trigger or LH surge, and thus patients are counseled to have an insemination during this timeframe and/or intercourse over the 3 days that follow. Intercourse every day and every-other-day is practically equally effective, with lower pregnancy rates as the interval increases.
Menses generally comes two weeks after the LH surge or trigger, unless pregnancy occurs. Low progesterone levels and a short luteal phase are usually indicative of a progesterone deficiency. We supplement these patients with progesterone and others at high risk, such as those with high prolactin levels, thyroid dysfunction or a history of pregnancy loss.