Paper Title
Fetal Sex and Placenta and Cord Characteristics in Twin Gestations?

Abstract
Background: Placenta plays a central role in mediating growth and development of fetuses. Sex-specific placentas may complicate this role. Objective: To study the association between fetal sex and placental pathological findings in twin gestations. Methods: A retrospective cohort of 1448 twin placentas was linked with clinical data of twins born in British Columbia Children and Women’s Hospital. Results: Twenty-six percent of twins were monochorionic and 74% were dizygotic. More than 50% of twins were male and 67.5% were sex discordant. Of sex-concordant twins, 35.1% were male-male and 32.3% were female-female. Adjusted for chorionicity, birth weight discordance (BWD) ≥30% and gestational age, the odds of chorionitis (OR1.38; 95%CI,1.04-1.84), anastomosis (1.63;1.22-2.19), unequal sharing of placenta (1.72;1.11-2.64), placental inflammation (1.30;1.05-1.62) and lesions (1.83;1.02-3.31) were higher in male twins compared with females. Twins of either sex from sex-discordant pairs were less likely to have placental anastomosis compared to the reference category. Males from male-male pairs had higher odds of unequal placental sharing (74% higher) and composite inflammation (52% higher) compared with the reference twins. Interpretation: Our findings suggest a relationship between sex and placental pathological results. Index Terms - Placenta, Cord, Pathology, Twin Pregnancy