The effect of hyoscine N-butylbromide on embryo transfer: a randomized clinical trial

The study aimed to assess whether the use of hyoscine N-butylbromide (Buscopan®) prior to embryo transfer (ET) improves the live birth rate (LBR) among patients undergoing in vitro fertilization (IVF)/ intracytoplasmic sperm injection (ICSI) treatment.

This prospective, double-blinded, randomized controlled trial was conducted at a university-affiliated hospital between May 2020 and April 2024. Of the 661 women randomized, 620 were analyzed. Forty-one women were excluded prior to embryo transfer due to cycle cancellation (n = 31) and other reasons (n = 10). Eligible participants underwent ET in fresh or frozen cycles and received either a 1 ml intravenous injection of 20 mg hyoscine N-butylbromide or 1 ml of normal saline before the procedure. Uterine contractions were recorded using 2-dimensional ultrasound scans. Reproductive outcomes, including implantation, clinical pregnancy, live birth, multiple pregnancy, miscarriage, and ectopic pregnancy rates, were evaluated.

The LBR did not significantly differ between the hyoscine N-butylbromide and placebo groups (32.2% versus 33.3%, P = 0.774; odds ratio 0.952, 95% confidence interval: 0.680-1.332). Other reproductive outcomes, including implantation, clinical pregnancy, miscarriage, and multiple pregnancy rates showed no significant differences between the two groups, and no ectopic pregnancies were reported. Subgroup analysis based on uterine contraction frequency indicated similar reproductive outcomes across high and low contraction frequency groups.

While hyoscine N-butylbromide is known for its myometrial smooth muscle relaxation effects, this study did not conclusively demonstrate improved reproductive outcomes following its use before ET.