What factors are linked to spontaneous miscarriage after assisted reproduction?

This study investigated the factors linked to spontaneous miscarriage (sMC) after assisted reproduction (AR). 

They found that sMC rates were higher in patients under 35 years with uterus (womb) malformations (UMs) and polycystic ovarian syndrome (PCOS). 

Assisted reproduction (AR) has improved fertility outcomes for a great many couples. In vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) are AR techniques. Clinical pregnancy rates (CPR) can be as high as 60% with IVF or ICSI. However, the rates of negative fertility outcomes are also higher. Spontaneous miscarriage (sMC) is more common after IVF than natural conception. 

There are many factors that may affect sMC rates. Women undergoing IVF are usually older. This means the number and quality of the embryos declines with age. Fertility disorders may also affect SMC. Polycystic ovarian syndrome (PCOS) and endometriosis (EDMT) are associated with increase sMC risk. It is unclear if these factors affect SMC rates in patients undergoing IVF/ICSI. 

This study included 21,485 clinical pregnancy cycles. Patients underwent either IVF or ICSI. The primary outcome was the sMC rate. 

The sMC rate was 12.58% in all pregnancy cycles included. SMC rate varied with age and infertility diagnosis. The sMC rate was significantly higher in patients with a higher body mass index (BMI; a measurement of weight in relation to height).

In patients under 35 years, the sMC rate was higher in patients with a uterus malformation (UM; 14.44% vs. 9.47%). The sMC rate was also higher in patients under 35 with PCOS (11.43% vs.  9.47%). This effect was not seen in patients over 35. Frozen embryo transfer (Fz-ET) was associated with a 45% higher risk of sMC in patients under 35. The risk of sMC was 21% lower with Fz-WT in patients over 35.

The authors concluded that sMC rates were higher in patients under 35 with UMs and PCOS.

This study was based on medical records. Some patient details were not available for the analysis. There could be other factors that may affect sMC.