Successful pregnancy and live birth despite discontinuation of hormone replacement therapy at 3 weeks and 5 days of gestation following vitrified-warmed embryo transfer under a hormone replacement therapy cycle: a case report and literature review.

backgroundIn freeze-thawed embryo transfer (FET) cycles, hormone replacement treatment (HRT) is crucial for implantation and pregnancy maintenance. HRT typically continues until the 10th week of pregnancy owing to a luteoplacental shift, although a definitive HRT regimen remains undetermined. We present the case of a woman who underwent FET during an HRT cycle and ceased HRT after a negative pregnancy test at 3 weeks and 5 days, who went on to deliver a healthy baby. CASE PRESENTATION: A 30-year-old Japanese woman with primary infertility was scheduled for FET. Estrogen supplementation was initiated as part of the HRT cycle for endometrial preparation. After achieving an endometrial thickness of 8 mm, progesterone supplementation was commenced, and the transfer of a 4BB blastocyst occurred 5 days after initiating progesterone treatment. At a gestational age of 3 weeks and 5 days, her serum human chorionic gonadotropin (hCG) level was only 8.3 mIU/mL, leading to discontinuation of HRT due to the absence of pregnancy. However, at 6 weeks and 1 day, her serum hCG levels significantly rose to 9359 mIU/mL, prompting the resumption of HRT. Ultrasonography confirmed the presence of a gestational sac and cardiac activity in the uterus, and HRT was continued until the 10th week. Ultimately, she delivered a healthy female neonate vaginally, weighing 2601 g at 40 weeks and 6 days.

conclusionsProgesterone supplementation is customary in FET with HRT cycles, although it has raised the possibility that there is demonstrating the potential for an ongoing pregnancy and resulting in a healthy baby under no progesterone replacement prior to the luteoplacental shift in this case. The duration and dosage of progesterone in luteal support for FET with HRT warrant further investigation.