Weekly injected progesterone – does it reduce miscarriage risk after embryo transfer?

This study investigated if weekly intramuscular progesterone (IM-PG) reduces miscarriage (MC) risk in women seeking assisted reproduction (AR). They found that weekly IM-PG may reduce the risk of MC in these women.

Progesterone (PG) is an important hormone in pregnancy. PG helps prepare the uterus for pregnancy. It helps the uterus lining (endometrium) to thicken. If PG levels fall then a miscarriage (MC) can occur. PG is also important in assisted reproduction (AR). In AR, eggs (oocytes) are fertilized in a laboratory. These fertilized embryos are then transferred to the uterus. PG is administered to prepare the uterus before embryo transfer (ET). 

PG can be administered in two ways. It can be injected directly into the muscle (IM). It can also be applied locally to the vagina (IVG). Most doctors chose IVG-PG as it achieves a high concentration of PG in the uterus. However, the concentration of PG in the blood is low after IVG-PG. Some studies suggest blood PG levels are important to reduce MC risk.  It is unclear if IM-PG can reduce MC risk in women undergoing ET and which is the moment when PG can be started.

This study included couples undergoing ET. 186 oocyte donation cycles were included. All women underwent IVG-PG treatment before ET. Pregnancy was confirmed 14 days after ET. One group of patients continued receiving IVG-PG alone (group 1; 106). One group of began IM-PG treatment weekly after pregnancy confirmation (group 2; 29). The third group received IM-PG weekly from the day of ET (group 3; 51). PG treatment lasted until the end of the first trimester or after MC. The main outcomes were MC rate and live birth rate (LBR).

There was no difference in PG levels after pregnancy confirmation. MC rate was lower in patients from group 3 (16.7%) compared to group 1 (47%) and group 2 (46.2%). LBR was significantly higher with IM-PG after ET (37.3%). This was compared to LBR with IVG-PG only (16%) and IM-PG after pregnancy confirmation (24.1%).

The authors concluded that IM-PG administered weekly from the day of ET may reduce the risk of MC in women seeking AR.

This study was based on medical records. Patients were not randomly assigned to treatment. This means the results could be biased. Also, the study groups were not equal. More investigation is needed.