Uterine peristalsis exerts control over fluid migration after mock embryo transfer

Abstract

Study question: What is the effect of uterine peristalsis on fluid migration after mock embryo transfer?

Summary answer: Uterine peristaltic wave frequency was positively correlated with the distance that fluid moved after it was deposited in the uterine cavity.

What is known already: Embryos have been found outside the uterine cavity after embryo transfer. It has been suggested that uterine contractions expelled these embryos.

Study design, size, duration: A prospective cohort study of a total of 112 infertile women was conducted between March 2013 and May 2013.

Participants/materials, setting, methods: Uterine peristaltic activity was assessed before and after a mock embryo transfer, in which 20 µl of ultrasound contrast agent was placed in the uterine lumen 3 days after ovulation in a natural cycle. The movement of this fluid was measured by ultrasound at 0, 15 and 30 min after placement.

Main results and the role of chance: The uterine peristaltic wave frequency was significantly higher after than before mock transfer (3.06 ± 0.99 versus 2.24 ± 0.74, P < 0.01). At the conclusion of the 30-min monitoring period, the fluid had remained in place (N = 94), leaked into the cervix (N = 5), or moved into the Fallopian tubes or the cornua of the uterus (N = 11). The fluid movement was positively correlated with uterine peristaltic wave frequencies before (r = 0.518, P < 0.01) and after embryo transfer (r = 0.371, P < 0.01) and uterine peristaltic wave frequency was significantly higher both before and after embryo transfer in cases where the fluid was extruded.

Limitations, reasons for caution: Mock embryo transfer was performed in the luteal phase of a natural cycle instead of a controlled ovarian stimulation cycle. The endometrial environment and uterine peristalsis may be different in a stimulated cycle.

Wider implications of the findings: Uterine peristalsis exerts control over embryo migration and could adversely affect the chances of pregnancy if the wave frequency is too high. It could be used as a predictor of uterine irritability before embryo transfer.

Study funding/competing interest(s): The authors declare that they have not received any particular study funding and do not have competing interests in this study.

Keywords: assisted reproductive technology; fluid migration; uterine peristalsis; uterine receptivity.