The effect of peri-implantation administration of uterine relaxing agents in assisted reproduction treatment cycles: a systematic review and meta-analysis

Abstract

Sub-endometrial junctional zone peristalsis is increased by ovarian stimulation and traumatic embryo transfer, and is linked with decreased implantation and pregnancy rates in assisted reproduction treatments. Various agents have been used to inhibit uterine hyper-peristalsis at the time of embryo transfer with conflicting results. This systematic review aimed to identify if uterine relaxants administered in the peri-implantation period during assisted reproduction treatments could improve pregnancy outcomes through literature search with no language restrictions. The review reports on 3546 patients in 17 randomized controlled trials published between 1993 and 2014. Women undergoing assisted reproduction techniques who either received a uterine relaxant agent in the peri-implantation period versus placebo or no treatment were included. Primary outcome was live birth rate. The meta-analyses did not show statistically significant benefit of any uterine relaxing agents on live birth rate. Other meta-analyses did not show a significant effect on the clinical pregnancy, spontaneous abortion, ectopic pregnancy and multiple pregnancy rate. Most of the included studies were of low quality and lacked significant power to detect minimally important effect. Evidence is insufficient to recommend using these agents in routine practice. Further methodologically robust randomized controlled trials with more refined selection criteria might reveal a beneficial effect.

Effects of pre-pregnancy body mass index on pregnancy and perinatal outcomes in women with PCOS undergoing frozen embryo transfer

“…The higher rate of caesarean sections may be partially related to the higher rate of complications in the obese/overweight women, however, there is data to suggest that this difference is not completely explained by the high-risk obesity-associated conditions alone [26]. High caesarean section rates have been documented in otherwise low-risk obese/overweight women, and it is therefore plausible that being obese/overweight itself is an independent risk factor for labor dystocia, resulting in increased caesarean section [27–29].…”

Obesity alters the uterine environment before pregnancy

“…It has been shown that difficult embryo transfer stimulates uterine contractions and this has been postulated to lead to non-adherence of the embryo(s) to the endometrium, expulsion of the embryos from the uterine cavity shortly after embryo transfer, or both [50]. The same finding has been reported in a small study in natural cycles [51].…”

The effect of early administration of rectal progesterone in IVF/ICSI twin pregnancies on the preterm birth rate: A randomized trial

“…Another meta-analysis attempting at reducing subendoemtrial contractility at time of ET to increase pregnancy rates didn't show any benefit using various agents (48) In the latest report by the ICMART [21] including data from the years 2008-2010, single embryo transfer (SET) increased from 25.7% to 30% with a resulting drop in Multiple twin births to 19.6% & the triplets to 1.0%. Individual European countries with strict single embryo transfer policies such as Sweden have 76.9% of their transfers SET and a resulting 5.4 % only twin births [49].…”