Abstract Study question What is the effectiveness of oil-based contrast during HSG compared to water-based contrast? Summary answer HSG with oil-based contrast increased the live birth rate as compared to water-based contrast. What is known already Tubal flushing has long been thought to increase live birth rate in infertile couples. A large randomised clinical trial (RCT) in The Netherlands confirmed the long-term hypothesis that HSG with oil-based contrast (Lipiodolâ) increased the live birth rate as compared to HSG with water-based contrast. We assessed whether this treatment effect was also achieved with oil-based contrast in Chinese women. Study design, size, duration We performed a prospective cohort study between May 4, 2020 and March 30, 2022. A total of 1187 women were included in the analysis.These women were categorized into two groups based on the contrast they used: the Oil-Soluble Contrast Media (OSCM) group, which employed poppy seed oil, consisting of 569 cases, and the Water-Soluble Contrast Media (WSCM) group, which used iodixanol, comprising 618 cases. Participants/materials, setting, methods This study was conducted at Shanghai Jiao Tong University International Peace Maternity and Child Health Hospital .The primary outcome was ongoing pregnancy rate within 6 months after the examination.Secondary outcomes included clinical pregnancies, miscarriage, ectopic pregnancy and thyroid Stimulating Hormone. Main results and the role of chance The ongoing pregnancy rate of the oil group is significantly higher than that of the water group (24.1% versus 17.2%, rate ratio [RR], 1.53; 95% confidence interval [CI], 1.14 to 2.06; P = 0.004). Women in the oil group also achieved higher clinical pregnancy rate (32.2% versus 22.2%, RR, 1.67; 95% CI, 1.27 to 2.18, P < 0.001), higher live birth rate (23.9% versus 16.8%, RR, 1.56; 95% CI, 1.16 to 2.09, P = 0.003), and bore higher risk of miscarriage (8.0% versus 5.0%, RR, 1.67; 95% CI, 1.02 to 2.72, P = 0.04) than water group. Limitations, reasons for caution The sample size along with the data was obtained from a cohort study in a single center. Wider implications of the findings Tubal flushing with oil-based contrast medium is an effective treatment to improve the pregnancy outcomes of infertile women that should be part of every infertility work-up. Trial registration number not applicable
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