Determining ongoing pregnancy following frozen-embryo transfer: what is the cut-off for progesterone levels?

This study investigated if progesterone (PGO) levels determine ongoing pregnancy after hormone replacement therapy frozen embryo transfer (HRT-FET).

They found that the PGO levels below 35 nmol/l lower the chance of ongoing pregnancies.

Infertility is a condition that is becoming increasingly more common. There are a number of assisted reproductive technologies (ART) that can be used to achieve pregnancy. Some patients will choose to use in vitro fertilization (IVF) to fertilize embryos and transfer them into the uterus (womb). Embryos can be frozen and then thawed before transfer (frozen embryo transfer, FET).  In order to achieve a pregnancy, the uterus must be primed to receive the embryo.

Hormone replacement therapy (HRT) can be used to prime the uterus. Patients take a combination of estrogen and progesterone (PGO) to mimic hormone levels during natural embryo implantation. PGO is important for ongoing pregnancy. It allows the embryo to attach to the uterus and grow. It is unclear how much PGO is needed for ongoing pregnancy following HRT-FET.

This study included 244 HRT-FET cycles. Patients were treated with oestradiol valerate (oestrogen) and PGO. PGO levels were on day 9 or 11 after HRT-FET, the day of pregnancy testing. At 7 and 12 weeks of pregnancy, an ultrasound was performed to detect a heartbeat (clinical pregnancy) and confirm a pregnancy.

45% of cycles resulted in an ongoing pregnancy at 12 weeks. Patients with PGO lower or equal to 35 nmol/L had poorer implantation rates than PGO levels greater than 35 nmol/l (37% vs. 50%). The clinical pregnancy rates were reduced in the lower PGO group (40%) vs. 54% in the higher PGO group. The ongoing pregnancy rate was significantly higher (51%) in cycles with PGO greater than 35 nmol/L compared to 38% in the low PGO group. The chance of ongoing pregnancy was 14% lower for cycles with PGO lower than 35 nmol.

The authors found that PGO levels below 35 nmol/l lower the chance for ongoing pregnancies during HRT-FET cycles.

This study is looked back at medical records, so there may be information missing.  

If you have any concerns regarding fertility treatment, please consult with your doctor.