Letrozole vs. clomiphene citrate – which is more effective for ovulation induction in women with unexplained infertility?

This study compared clomiphene citrate (Clomid) and letrozole (Femara) for ovulation induction (OI) drugs in women with unexplained infertility. 

They found that letrozole was associated with lower miscarriage rates (MCRs). 

Unexplained infertility is a leading cause of infertility. Assisted reproduction (AR) can be used to treat this. Ovulation induction (OI) is one option. OI can be used to stimulate the release of mature oocytes (eggs) from the ovaries. These can be harvested for in vitro fertilization (IVF). Another option is intrauterine insemination (IUI). This involves delivering sperm into the uterus. 

OI uses medications that stimulate the release of eggs. Clomiphene citrate (CC) is an OI drug. It was the first drug used for OI. CC stimulates the release of estrogen. This is called pro-estrogen effect (PEE). This causes the release of mature oocytes. CC can also have anti-estrogen effects (AEEs). This can reduce endometrium thickness (EMT). This can make it more difficult for an embryo to implant. Letrozole is another drug that can be used for OI. It only has PEEs. It is unclear if LE has better fertility outcomes compared to CC in women with unexplained infertility.

This study analyzed 6 clinical reports with 3413 women who underwent IUI. OI was performed with either letrozole or CC. Fertility outcomes including pregnancy (PRs) and miscarriage rates (MCRs) were analyzed. The number of mature follicles was also analyzed. 

There was no difference in PRs between the groups. There was also no difference in the number of follicles, multiple pregnancies, or EMT. However, the MCR was 39% lower in letrozole-treated women. 

The authors concluded that letrozole was associated with lower miscarriage rates compared to clomiphene in women with unexplained infertility undergoing ovulation induction.

There were many differences in some data. This included data on MCRs and EMT. There was no evidence on live birth rates in this study. Larger controlled studies are needed. 

If you have any concerns regarding infertility please consult with your doctor.