This is a multicenter double-blind randomized controlled trial. A total of 420 anovulatory Chinese women with PCOS will be recruited, and the randomization will be stratified by each participating site. Participants will be randomized into one of the two treatment arms: letrozole and CHMG or letrozole and CHMG placebo. CHMG or its placebo will be taken twice a day for up to six months. Letrozole (2.5 mg daily) was given on days 3-7 of the menstrual cycle after a spontaneous period or withdrawal bleeding, and the dose will be increased to 5.0 mg daily during the last three months for non-pregnant women in both groups.The aim of the present study is to determine the efficacy of combined treatment with letrozole and CHMG on improving live birth rates in infertile Chinese women with PCOS. Our hypothesis is that the combination of letrozole and CHMG is more likely to increase the ovulation rate and decrease the miscarriage rate and result in a higher live birth rate in PCOS women than letrozole alone.

Inclusion criteria

1. Chinese women with PCOS. PCOS must have been diagnosed based on the presence of two of the following three Rotterdam criteria : (1) oligomenorrhea, anovulation; (2) hyperandrogenism; and (3) the observation of polycystic ovaries by sonography. Oligomenorrhea is defined as an intermenstrual interval >35 days or <8 menstrual bleedings in the past year. Amenorrhea is defined as an intermenstrual interval >90 days.
2. History of at least one year of infertility.
3. Age between 20 and 40 years old.
4. Normal semen analysis based on World Health Organization criteria (2010). The husband did not need to sign the consent form because semen analysis is part of the clinical assessment at the sites. A sperm concentration ≥15 × 106/mL and total motility ≥40% in the semen analysis of the husband was required for the woman to be included.
5. Normal uterine cavity and at least one tube patent upon hysterosalpingography or HyCoSy.

Exclusion criteria

1. History of significant system diseases such as heart, lung, or kidney diseases.
2. History of other endocrine disorders.
3. Use of hormonal therapy, including metformin, in the past 3 months.
4. Previous sterilization procedures (vasectomy or tubal ligation) that have been reversed.