Assessing response to ovulation induction
Confirming ovulation after induction
Ovulation is confirmed by measuring the serum progesterone concentration in the midluteal phase (5 to 10 days before the start of menstruation).
If ovulation does not occur, usual practice is to increase the daily dose of letrozole or clomifene for each of the next two cycles, before considering gonadotrophins.
If ovulation is confirmed, but pregnancy fails to occur after three to six cycles of treatment with letrozole or clomifene, other causes of infertility should be excluded before further treatment is considered. Assessment includes tests of fallopian tube patency and uterine imaging (eg hysterosalpingogram, hysteroscopic contrast sonography [HyCoSy]) and laparoscopy with dye tests.
Assessing for multiple follicles in ovulation induction
All individuals taking drugs to induce ovulation must be monitored by an experienced clinician because there is a risk of multiple follicles developing. Multiple follicles may develop into a multiple pregnancy (in a few percent of conceptions) or cause ovarian hyperstimulation syndrome (OHSS). These risks are slightly increased with clomifene and letrozole, but are substantial with gonadotrophins.
OHSS is rare with ovulation induction, and is more likely with in-vitro fertilisation (IVF). Individuals may present directly to their general practitioner with symptoms of OHSS. The severity is very variable, but OHSS can be life-threatening, so it is important to be aware of the features and approach to assessment of OHSS.
Monitoring for multiple follicles involves ultrasound investigations and laboratory tests (including serum estrogen concentrations). If multiple follicles do develop, adverse effects may be avoided by cancelling the treatment cycle, avoiding unprotected intercourse and not giving an ovulation trigger (eg high-dose hCG).