Overview

This randomized trial we aim to compare the live birth rate of immediate versus delayed FET replacing a single blastocyst in the first FET of the first stimulated IVF cycle following. The hypothesis is that the live birth rate of the immediate FET is higher than the delayed FET replacing a single blastocyst in the first FET of the first stimulated IVF cycle following a freeze-all strategy. Women will undergo IVF/ICSI in the centre as clinically indicated. Standard ovarian stimulation with gonadotrophins in a Gonadotrophin releasing hormone (GnRH) antagonist protocol will be employed. Hormone replacement treatment (HRT) will be used in subsequent FET cycles. On Day 3 of the menstrual cycle, we will measure the anxiety levels using the Chinese State-Trait Anxiety Inventory and serum E2, cortisol levels will be checked on the same day.

Recruited women having the first FET cycle following a freeze all strategy will be randomly assigned on the day of blastocyst(s) freezing according to a computer-generated randomization list into one of the following two groups.

Eligibility

Inclusion Criteria:

1. Women aged 20-40 years at the time of IVF/ICSI
2. Women undergoing their first FET of the first IVF cycle following a freeze-all strategy
3. Undergoing IVF with GnRH antagonist
4. At least one frozen blastocyst

Exclusion Criteria:

1. Severe ovarian hyperstimulation syndrome during the first IVF/ICSI cycle
2. Preimplantation genetic testing
3. Use of donor oocytes
4. Presence of untreated hydrosalpinx or endometrial polyp on scanning during ovarian stimulation