The timing of Clomid could increase ovulation and pregnancy rates

This study examined whether the timing of clomiphene citrate affects ovulation and pregnancy rates in women with polycystic ovarian syndrome.

Polycystic ovarian syndrome is the most common cause of anovulation, or lack of regular ovulation. Women with polycystic ovarian syndrome are at a high risk for infertility and miscarriage. Despite this being a common disorder, it is still not clear which treatments are most effective for dealing with infertility in patients with this syndrome.

The most common treatment is ovulation induction (triggering) with clomiphene citrate (Clomid), a drug treatment which is used for 5 days, starting on the fifth day of menstruation. Clomiphene is successful at triggering hormones that cause ovulation in 60 – 85% of women, but pregnancy rates are only 20 – 40%. One theory as to why pregnancy rates are much lower than the ovulation rates is that clomiphene can have a negative effect on the lining of the uterus, which should increase in thickness over the course of the menstrual cycle, and is essential for the proper implantation of a fertilized egg. It is possible that beginning clomiphene earlier than the fifth day of the menstrual cycle may stop these negative effects extending into the sensitive implantation period. The current study examined whether the timing of clomiphene treatment affected ovulation, uterine lining formation, and pregnancy in women with polycystic ovarian syndrome.

252 women with polycystic ovarian syndrome were randomly assigned to one of two groups: Group 1 received 100 mg of clomiphene daily for 5 days, starting on the fifth day of menstruation. Group 2 received 100 mg of clomiphene daily for 5 days starting just before the start of menstruation. The number of growing follicles (where the egg is released from the ovary), the thickness of the uterine lining, and rates of pregnancy were measured.

There was an increase in ovulation rates for Group 1 (64.3%) compared to Group 2 (56.3%), but this difference was not statistically significant. Group 2 saw more and larger follicles, and a 1 millimeter increase in the thickness of the uterine lining. Miscarriage rates (2.4%) were not different between the two groups, but pregnancy rates were slightly higher in Group 2 (10.3%) compared to Group 1 (8.7%).

This study concluded that starting clomiphene citrate earlier in the menstrual cycle can increase the number of growing follicles and the thickness of the uterine lining.

However, though the authors suggest that starting clomiphene earlier could help raise the rates of pregnancy, they did not report a significant increase. Therefore, further studies, including a larger number of patients should be done to lend more evidence.