This study used data from the Swedish Medical Birth Registry between 1982 and 1995 to address the question of whether there is higher mortality in twins in relation to singletons of the same gestational age and to examine the optimal gestational age range for twins. A "varying-coefficient approach" was adopted to estimate the gestational age-specific relative and absolute risks of mortality in ...

Rare variants are important for drawing inference about past demographic events in a species history. A singleton is a rare variant for which genetic variation is carried by a unique chromosome in a sample. How singletons are distributed across geographic space provides a local measure of genetic diversity that can be measured at the individual level. Here, we define the empirical distribution ...

BACKGROUND The purpose of this study was to assess the effect of a vanishing twin on the risk of being small-for-gestational age (SGA) in in vitro fertilization (IVF) singletons. METHODS The study included 642 survivors of a vanished co-twin, 5237 primary singletons and 3678 primary twins. The survivor cohort was subdivided according to gestational age at the time of vanishing to give groups ...

BACKGROUND Spontaneous reductions are a possible cause of the increased morbidity in IVF singletons. The aim of this study was to assess incidence rates of spontaneous reductions in IVF/ICSI twin pregnancies and to compare short- and long-term morbidity in survivors of a vanishing co-twin with singletons and born twins. METHODS We identified 642 survivors of a vanishing co-twin, 5237 singleto...

STUDY QUESTION Is there a difference in birthweight distribution in ART singletons born after IVF culture in two different culture media? SUMMARY ANSWER There is no effect of culture media on both crude and adjusted birthweight distributions in ART singletons from nulliparous mothers. WHAT IS KNOWN ALREADY Studies on human ART singletons have reported a difference in birthweight in singleto...

The first half is a rapid review of 30 years of work on physics in antiDe Sitter space, with heavy emphasis on singletons. Principal topics are the kinematical basis for regarding singletons as the constituents of massless particles, and the effect of (negative) curvature in the infrared domain. Ideas that lead to an alternative to Big Bang cosmology are merely sketched. The second half present...

OBJECTIVE To determine whether the apparent additional and exceptional stresses associated with bearing and parenting twins affect the emotional wellbeing of mothers. SETTING Great Britain, 1970-5. DESIGN Cohort study of 13,135 children born between 4 April and 11 April 1970. Mothers of all children, both singletons and twins, were interviewed by health visitors (providing demographic data)...

OBJECTIVES To examine whether infertile couples (with a time to pregnancy of > 12 months), who conceive naturally or after treatment, give birth to children with an increased prevalence of congenital malformations. DESIGN Longitudinal study. SETTING Danish national birth cohort. PARTICIPANTS Three groups of liveborn children and their mothers: 50,897 singletons and 1366 twins born of fert...