The object of ovulation induction is to restore the ovulatory state and reinstate fertility potential for women who are not ovulating naturally. This should, ideally, produce one ovulatory follicle and should not be confused with controlled ovarian stimulation for in-vitro fertilization or for intra-uterine insemination (IUI) which is applied to already ovulating women with the aim of producing multiple ovulations.
The first step to successful induction of ovulation is to ascertain the cause of the lack of ovulation (anovulation) as this will determine the treatment. The commonest cause of anovulation is polycystic ovary syndrome (PCOS) in which case the first line treatment is with clomiphene citrate. Much less frequently, the cause of anovulation may be due to a lack of hormones (FSH and LH) from the pituitary gland in which case these two hormones are given by injection to stimulate the ovaries to ovulate. A third cause of anovulation is a premature menopause before the age of 40 but in this case ovulation induction is impossible and egg donation is the only way to conceive.
Clomiphene citrate is a simple cheap treatment with almost no side effects. It is given in the form of tablets, usually from day 4 of the cycle for 5 days. By causing an output of follicle stimulating hormone (FSH) from the pituitary gland, ovulation is restored in about 75% and pregnancy is achieved in about 35%. A twin pregnancy rate may be expected in 8%. Failure to conceive with clomiphene indicates the use of injectable daily FSH to induce ovulation.
The complications of ovulation induction with FSH are multiple pregnancies and ovarian hyperstimulation syndrome (OHSS). They are both caused by the induction of multiple ovulations and are largely preventable. Both can be avoided by using just enough FSH to stimulate one ovulation in a ‘low and slow’ protocol.