The purpose of this systematic review was to evaluate the efficacy of pretreatment
with letrozole prior to either a first- or second-trimester medical termination of
We searched letrozole, femara, aromatase inhibitors, abortifacient agents, termination
of pregnancy and labor induction in MEDLINE, EMBASE, Cochrane Database, Google Scholar
and PubMed from inception of each database until September 2015 with no language limitation.
A systematic review of all randomized controlled trials (RCTs) was performed where
women received either letrozole and misoprostol or placebo and misoprostol for termination
of pregnancy. The primary outcome was complete abortion rate, defined as complete
evacuation of the products of conception from the uterus. Relative risk with 95% confidence
intervals was used to report data.
Our systematic review identified 7 studies; 4 RCTs were included in the review. Two
RCTs evaluated terminations of pregnancy up to 9 weeks’ gestation, while 2 evaluated
terminations over 9 weeks’ gestation. For each gestational age group, one trial supported
an increase in complete abortion rate, while the other showed no difference, with
letrozole and misoprostol compared with placebo and misoprostol. Time-to-abortion
interval for terminations up to 9 weeks’ gestation was not improved with the addition
of letrozole to misoprostol. For terminations over 9 weeks’ gestation, one trial supported
and one trial refuted a decrease in time-to-abortion interval with letrozole and misoprostol.
Similarly, for each gestational age group, one study supported a decrease and one
study showed no difference in rate of dilation and curettage (D&C) with letrozole
and misoprosol. Medication side effects were similar between both treatment groups.
There was significant heterogeneity between the trials, and therefore, the results
were not meta-analyzed.
Some studies and trials report better outcomes (i.e., complete abortion rates, time-to-abortion
and D&C rates) in women exposed to letrozole and misoprostol compared to placebo and
misoprostol, while other trials demonstrate no difference. Further research exploring
letrozole pretreatment prior to medical abortion is required.
This systematic review demonstrated that a combination of letrozole and misoprostol
increased the rate of complete abortion compared to misoprostol alone in some studies
but not in others; additional well-designed RCT's are needed.