Polycystic ovary syndrome is a common endocrine disorder, characterized by hyperandrogenism
and/or chronic oligo/anovulation, which leads to infertility. The aim of this systematic
review and meta-analysis was to explore the efficacy of letrozole compared with clomiphene
citrate for ovulation induction in women with polycystic ovarian syndrome. The study
protocol has been registered with PROSPERO (registration number CRD42022376611). The
literature search included randomized clinical trials. We conducted our systematic
literature search across three medical databases: MEDLINE (via PubMed), Cochrane Library
(CENTRAL), and Embase. The data synthesis employed a random effects model. Out of
the 1994 articles screened, 25 studies fulfilled the inclusion criteria. The letrozole
group exhibited a significant increase in endometrial thickness (mean difference =
1.70, confidence interval: 0.55–2.86; I2 = 97%, p-value = 0.008). The odds of ovulation
(odds ratio = 1.8, confidence interval: 1.21–2.69; I2 = 51%, p-value = 0.010) and
pregnancy (odds ratio = 1.96, confidence interval: 1.37–2.81; I2 = 32%, p-value =
0.002) were significantly higher. The resistance index of the subendometrial arteries
showed a significant decrease (mean difference = −0.15, confidence interval: −0.27
to −0.04; I2 = 92%, p-value = 0.030). Women diagnosed with polycystic ovarian syndrome
and treated with letrozole for ovulation induction had increased ovulation and pregnancy
rates and increased endometrial thickness. The lower resistance index of subendometrial
arteries can enhance intrauterine circulation, creating more favorable conditions
for embryo implantation and development.
