El‐Toukhy 2004.

Methods	Single‐centre parallel RCT
Participants	234 women Inclusion criteria: women with functioning ovaries and regular menstrual cycles who had surplus embryos frozen following fresh ET in a cycle of IVF or ICSI Exclusion criteria: FET originating from donated oocytes and women with irregular cycles. Number of transferred embryos per woman: HT group 2.2 ± 0.6, HT plus GnRHa group 2.3 ± 0.6 Baseline characteristics were similar in the 2 groups Infertility cause: similar (variety of causes)
Interventions	HT group (117 women) Estradiol valerate 6 mg/d/tablet started on day 1 of menstruation HT plus GnRHa group (117 women) Buserelin nasal spray was started in mid‐luteal phase (day 21) of cycle. On day 1 of subsequent cycle, oral E2 initiated as 6 mg/d in 2 divided doses In both groups, E2 dose continued for 12‐14 days then endometrial thickness was assessed by US. If endometrial thickness was < 8 mm, E2 dose was increased to 8 mg/d for further 7‐12 days Once 8 mm endometrial thickness had been confirmed, micronised progesterone pessaries 400 mg twice daily were commenced. GnRHa was stopped at this stage. There was no endocrine or US monitoring of ovulation. Embryos were transferred on day 3 of progesterone initiation. Progesterone use was for 2 weeks following FET. Pregnant women were advised to continue E2 and progesterone supplement up to 12th gestational week.
Outcomes	Clinical pregnancy rate per woman Miscarriage rate per clinical pregnancy Live birth rate per woman Cycle cancellation rate per woman Endometrial thickness prior to FET
Notes	Miscarriage rate per clinical pregnancy was used to calculate miscarriage rate per woman.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated random list
Allocation concealment (selection bias)	Unclear risk	Methods used in concealing the allocation not reported
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No reports on blinding of participants and personnel, although blinding of outcome assessor could not have influenced some of the reported outcome measures
Incomplete outcome data (attrition bias) All outcomes	Low risk	Analysis reported to have been performed on an ITT basis. ITT was not fully defined but it was apparent from 1 of the result tables that all participants randomized were included in data analysis (other aspects of ITT could not be verified)
Selective reporting (reporting bias)	Low risk	Data reported on all the outcomes prespecified in the methods section.
Other bias	Low risk	No other potential source of bias found.