01/05/2026
Research in a 2026 study found that bacteria detected on the embryo transfer catheter were linked to lower live birth rates, likely reflecting the patient’s own microbiome being carried into the uterus during transfer.
During embryo transfer, the catheter passes through the va**na and cervix, which are not sterile, meaning bacteria can be carried into the uterus and this may affect implantation.
A study by Boughanmi et al. (2026) measured bacteria in the va**na, cervix, and on the catheter after transfer, and compared this to pregnancy outcomes.
They found that when certain bacteria were present, live birth rates were much lower, while patients with more Lactobacillus had better outcomes. These bacteria were more common in patients with bacterial vaginosis (BV), a common and often unrecognized imbalance of the va**nal microbiome.
This suggests that the embryo transfer procedure itself may carry bacteria into the uterus, and that differences in the va**nal microbiome could quietly affect success rates.
The authors highlight BV as important, noting it can be screened for with a simple test. However, the study didn’t test whether treating BV or changing the microbiome improves outcomes, so this still needs to be confirmed.
