Are uterine contractions linked with IUI success?

Unlike with in vitro fertilization, it appears that uterine contractions may increase the chance of a successful intrauterine insemination (IUI), according to a new study in Fertility and Sterility.

In a retrospective study, researchers at the Valencian Infertility Institute in Spain analyzed data from 610 women who had undergone homologous or donor double IUI from 2005 to 2010 at the facility and also had uterine contractions and/or follicle rupture recorded. Myometrial contraction are theorized to be necessary to achieve fertilization and this is the first study to look at the association between uterine contractility post-IUI and cycle outcome.

Overall in the report, 979 IUI cycles were represented: 668 cycles in which the woman was inseminated with her partner’s sperm and 311 in which the woman was inseminated with donor sperm. Follicle rupture only was recorded for 605 cycles; uterine contractions only were recorded for 49 cycles; and 325 cycles recorded both variables.

The number of uterine contractions after the first IUI procedure was not correlated with either pregnancy or live-birth outcomes. However, there was a significant positive correlation between the number of uterine contractions after the second IUI procedure and the clinical pregnancy (odds ratio [OR], 2.13; 95% confidence interval [CI], 1.34-3.41; P=0.002) and live-birth rates (OR, 1.67; 95% CI, 1.02-2.74; P=.041). The correlation between uterine contractions and live-birth rate was only significant when both homologous and donor IUIs were looked at together.

Follicle rupture was significantly correlated with both the clinical pregnancy rate (OR, 1.72; 95% CI, 1.19-2.48; P=.004) and the live-birth rate (OR, 1.98; 95% CI, 1.30-3.01; P=0.01). No correlation was seen between follicle rupture and uterine contractions per minute and miscarriage or multiple pregnancy rates.

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The researchers indicated that one of the study’s main limitations was that uterine contractions were registered in far fewer patients than were follicle rupture. They recommend further studies with larger cohorts to help confirm their results.

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