Traditionally, it is understood that dizygotic (DZ) twins always have a dichorionic placenta. However, with 8% blood chimerism in DZ twins, placental sharing is probably more common than previously has been recognized. In this article, we will review all available cases of monochorionic dizygotic (MCDZ) twins. A total of 31 twins have been described in literature. A monochorionic diamniotic placenta is reported in all cases. Assisted reproductive technology is responsible for the origin of the pregnancy in 82.1% of the cases. In 15.4% of the sex-discordant twins, a genital anomaly was reported in one of the twins. Chimerism is demonstrable in 90.3% of the twins, leading to various diagnostic difficulties. As this review shows that most MCDZ twins are discovered by accident, it can be argued that it is far more common than has been assumed until now. However, the prevalence is still unclear. Awareness of MCDZ twinning is important, with subsequently correct medical strategies. Similarly, the resulting (blood) chimerism is essential to consider in diagnostic procedures, pre- and postnatally. More research on the effect of placental transfusion between sex-discordant twins is required.

ObjectivesContradictory results have been reported regarding the association between polycystic ovary syndrome (PCOS) and cardiovascular disease (CVD). We assessed the cardiometabolic phenotype and prevalence of CVD in middle‐aged women with PCOS, compared with age‐matched controls from the general population, and estimated 10‐year CVD risk and cardiovascular health score.DesignA cross‐sectional study.Participants200 women aged >45 with PCOS, and 200 age‐matched controls.MeasurementsAnthropometrics, insulin, lipid levels, prevalence of metabolic syndrome and type II diabetes. Ten‐year Framingham risk score and the cardiovascular health score were calculated, and carotid intima‐media thickness (cIMT) was measured.ResultsMean age was 50.5 years (SD = 5.5) in women with PCOS and 51.0 years (SD = 5.2) in controls. Increased waist circumference, body mass index and hypertension were more often observed in women with PCOS (P < .001). In women with PCOS, the prevalence of type II diabetes and metabolic syndrome was not significantly increased and lipid levels were not different from controls. cIMT was lower in women with PCOS (P < .001). Calculated cardiovascular health and 10‐year CVD risk were similar in women with PCOS and controls.ConclusionsMiddle‐aged women with PCOS exhibit only a moderately unfavourable cardiometabolic profile compared to age‐matched controls, even though they present with an increased BMI and waist circumference. Furthermore, we found no evidence for increased (10‐year) CVD risk or more severe atherosclerosis compared with controls from the general population. Long‐term follow‐up of women with PCOS is necessary to provide a definitive answer concerning long‐term risk for CVD.

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