The Outcome of 150 Babies Following the Treatment With Letrozole or Letrozole and Gonadotropins

Letrozole is a medication widely used for secondary breast cancer prevention. Recently, this aromatase inhibitor has been used for ovulation induction. In this analysis we report the outcome of 150 babies born as a result of treatment with either letrozole alone or a combination of letrozole and gonadotropins at the Montreal Fertility Centre. Retrospective analysis. This analysis includes patients with unexplained infertility and patients with polycystic ovarian disease. As a control group we used patients delivered at "St. Mary's" hospital in Montreal between 1995 and 2004. The choice of the hospital was deliberate, as "St. Mary's" hospital delivers mostly low risk babies. During a period of 25 months 171 babies were born as a result of the use of letrozole or letrozole and gonadotropins. Twenty one babies were lost for follow-up. One hundred and fifty babies were compared with a data-base of normal deliveries containing 36,050 deliveries. The median age (M) of treated patients was 35.2 years (interquartile difference (IQD)= 31.4-37.9). We had 110 singleton and 20 twin pregnancies. All twin pregnancies apart of one were conceived following the treatment with letrozole and gonadotropins. The incidence of vaginal bleeding was 36.7% in the first trimester, 7.3% in the second trimester, and 1.3% in the third trimester. Seventy-seven non-diabetic singleton pregnancies were delivered at term. There was no difference in weight between this group and the control. Twenty patients had gestational diabetes. Seventeen patients with gestational diabetes delivered at term. When compared with controls these babies were of a significantly lower birth weight than controls (p<0.002 95%CI=11.3-136.6). Incidence of all malformations was not different between the two groups (p=0.25 95%CI=0.78-4.71). However, the incidence of locomotor malformations (p=0.0005 95%CI=2.64-27.0) and cardiac anomalies (p=0.0006 95%CI=3.30-58.1) was higher than in the control groups. The results of this study show that use of letrozole in ovulation induction should be controlled until more data on outcomes of pregnancies is obtained.