title: Recent decelerated decline in perinatal mortality rate of unlike-sexed twins in Japan.
abstract: The effect of assisted reproductive technology is more pronounced in unlike-sexed twins than in like-sexed. Trends in perinatal mortality of twins were compared between the two types of sex combination. Certificates for births (478,276 cases), stillbirths (50,542 cases), and early neonatal deaths (8747 cases) were the subjects of this analysis. Since 1984, the decline in the perinatal mortality of unlike-sexed twins has been slower than that of like-sexed twins. In both light-for-dates (LFD) and non-LFD, the decline in the gestational age standardised mortality ratio has been slower in unlike-sexed twins. We suggest this is due to the introduction of assisted reproductive technologies.
authors.affiliation: Department of Health Promotion and Research, National Institute of Public Health, Saitama, Japan. kato@niph.go.jp
authors.forename: Noriko
authors.initials: N
authors.lastname: Kato
mesh_terms: D001719:Birth Certificates; D001724:Birth Weight; D003644:Death Certificates; D005260:Female; D005865:Gestational Age; D006801:Humans; D007226:Infant Mortality / Q000639:trends*; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D007564:Japan; D008297:Male; D011247:Pregnancy; D011256:Pregnancy Outcome; D012737:Sex Factors; D014429:Twins, Dizygotic / Q000706:statistics & numerical data*; D014430:Twins, Monozygotic / Q000706:statistics & numerical data*