summary answer: Pregnancies among women with TS carry a substantial risk, particularly for hypertensive disorders. Potentially lifethreatening complications occurred in 3.3% of pregnancies. The neonatal outcomes were generally reassuring, with similar rates of preterm birth and low birthweight (LBW) as after conventional IVF and better than previously reported in deliveries after OD in women with TS.what is known already: OD pregnancies in women with TS are known to be high-risk pregnancies. study design, size, duration: This retrospective cohort study included 106 women with TS who delivered after OD (n ¼ 122 deliveries, n ¼ 131 newborns) in three Nordic countries (Finland, Denmark, Sweden) between 1992 and participants, setting and methods: Women with TS who delivered after OD in three Nordic countries were identified (n ¼ 110). Four women declined to participate or were lost to follow-up, thus 106 women were included in the study. The medical data from fertility clinics, antenatal clinics and the hospitals where the women had been treated and/or delivered were scrutinized.main results and the role of chance: In this cohort, the karyotype was 45,X in 44% of the women with TS. Ten women (9.4%) had a known cardiac defect before pregnancy. Single embryo transfer was performed in 70.3% of the cases and the multiple birth rate was 7.4%. In total, 35.0% of the pregnancies were associated with a hypertensive disorder including pre-eclampsia in 20.5%. Potentially lifethreatening complications occurred in four pregnancies (3.3%), including one woman with aortic dissection, one with mild regurgitation of the tricuspid and mitral valve, one with a mechanical heart valve who developed HELLP syndrome (haemolysis, elevated liver enzymes, low platelets) and one who underwent a post-partum hysterectomy due to severe haemorrhaging. Neonatal outcomes were reassuring, with a preterm birth rate of 8.0% and LBW rate of 8.8% in singletons. Major birth defects were found in 3.8% of the children. The perinatal mortality was 2.3% (3/131), including a set of extremely preterm twins.limitations, reasons for caution: Although this study was performed over a period of almost 20 years in three different countries, with a low drop-out rate and little missing data, much larger series are needed to assess rare events. This study also lacks an appropriate control group. Reproduction, Vol.28, No.6 pp. 1598-1609, 2013 Advanced Access publication on March 27, 2013 doi:10.1093/humrep/det082 Downloaded from https://academic.oup.com/humrep/article-abstract/28/6/1598/605487 by guest on 07 June 2019 wider implications of the findings: This study suggests that cardiovascular evaluation before and during pregnancy may contribute to favourable obstetric outcomes in many cases. Maternal outcomes were in agreement with the literature while neonatal outcomes were generally better than previously reported. The outcomes were consistent across the three countries, supporting generalizability to similar populations.