Preparing the uterus for frozen embryo transfer

This study compared two medication protocols to prepare the uterus for frozen embryo transfer (FET). It found that down-regulation ovulation-induction (DROI) led to higher pregnancy rates than a modified natural cycle (mNC).

In vitro fertilization (IVF) is an infertility technique in which eggs are collected and fertilized outside the body. It is becoming more common to freeze some or all of the embryos created through an IVF cycle. These frozen embryos can then be transferred back into the uterus through FET.

In order for FET to be successful, the uterus needs to be receptive to an embryo implanting. There are multiple ways to prepare the body for FET. The uterus is naturally receptive during the second half of the menstrual cycle, after ovulation. Modified natural cycle (mNC) FET times the transfer for after ovulation.

DROI is a recently developed method to prepare the uterus for FET. This method first reduces the body’s own hormones using GnRH agonist (Lupron). Then, gonadotropin hormones are used to stimulate the ovaries. DROI is similar to ovarian stimulation during IVF, but at lower doses. It is not clear how DROI compares to other methods.

This study included 360 patients who were undergoing FET. All of the patients had regular menstrual cycles and did not have reproductive health conditions such as endometriosis. Half were randomly assigned to DROI-FET, and the other half used mNC.

There was a trend toward more patients in the mNC group transferring two embryos, rather than 1 (76.16% vs. 67.31%). Despite this, there were significantly more pregnancies confirmed on ultrasound in the DROI group (69.87% vs. 50.33%). Significantly more of the embryos in the DROI group had implanted successfully (54.41% vs. 35.71%).

There were significantly more pregnancies of twins in the DROI group (21.15% vs. 12.58%). Twin pregnancies are more dangerous than single pregnancies for both the mother and babies.

Ovarian hyperstimulation syndrome (OHSS) is a complication in which the ovaries respond too strongly to fertility medications. There were no cases of moderate or severe OHSS in this study.

This study found that there was a higher implantation rate from DROI-FET than from mNC FET.

This is one of the first studies to use DROI for FET. These results should be confirmed with larger studies.