Female causes of infertility are associated with higher risk of preterm birth and low birth weight: analysis of 117 401 singleton live births following IVF

STUDY QUESTION: Does the cause of infertility affect the perinatal outcomes preterm birth (PTB) and low birth weight (LBW) following IVF treatment? SUMMARY ANSWER: The risk of PTB and LBW was higher with female causes of infertility-ovulatory disorders, tubal disorders and endometriosis-compared to unexplained infertility but the absolute increase in risk was low. WHAT IS KNOWN ALREADY: Infertility is associated with an increased risk of adverse perinatal outcomes. Risk of adverse perinatal outcomes is also higher following ART compared to spontaneous conceptions. Infertility can result from female and/or male factors or is unexplained when the cause cannot be delineated by standard investigations. Given that infertility and ART are contributory to the adverse perinatal outcomes, it is a matter of interest to delineate if the specific cause of infertility influences perinatal outcomes following IVF treatment. STUDY DESIGN, SIZE, DURATION: Anonymous data were obtained from the Human Fertilization and Embryology Authority (HFEA). The HFEA has collected data prospectively on all ART cycles performed in the UK since 1991. Data from 1991 to 2016 comprising a total of 117 401 singleton live births following IVF with or without ICSI (IVF +/- ICSI) for sole causes of infertility were analysed for PTB and LBW. Cycles having more than one cause of infertility and/or multiple births were excluded. PARTICIPANTS/MATERIALS, SETTING, METHODS: Data on all women undergoing stimulated IVF +/- ICSI treatment cycles were analysed to compare perinatal outcomes of PTB and LBW among singleton live births based on the cause of infertility (ovulatory disorders, tuba) disorders, endometriosis, male factor, unexplained). Logistic regression analysis was performed, adjusting for female age category, period of treatment, previous live births, IVF or ICSI, number of embryos transferred and fresh or frozen embryo transfer cycles. MAIN RESULTS AND THE ROLE OF CHANCE: Compared to unexplained infertility, the risk of PTB was significantly higher with ovulatory disorders (adjusted odds ratio (aOR) 1.31, 99.5% CI 1.17 to 1.46); tubal disorders (aOR 1.25, 99.5% CI 1.14 to 1.38) and endometriosis (aOR 1.17, 99.5% CI 1.01 to 1.35). There was no significant difference in the risk of PTB with male factor causes compared to unexplained infertility (aOR 1.01, 99.5% CI 0.93, 1.10). The risk of LBW was significantly higher with ovulatory disorders (aOR 1. 29, 99.5% CI 1.16 to 1.44) and tubal disorders (aOR 1.12, 99.5% CI 1.02 to 1.23) and there was no increase in the risk of LBW with endometriosis (aOR 1.1 I, 99.5% CI 0.96 to 1.30) and male factor causes (aOR 0.94, 99.5% CI 0.87, 1.03), compared to unexplained infertility. LIMITATIONS, REASONS FOR CAUTION: Although the analysis was adjusted for several important confounders, there was no information on the medical history of women during pregnancy to allow adjustment The limitations with observational data would apply to this study, including residual confounding. WIDER IMPLICATIONS OF THE FINDINGS: This is the largest study to address the causes of infertility affecting perinatal outcomes of PTB and LBW. The information is important for the management of pregnancies and the underlying reasons for the associations observed need to be further understood.