Twin Births In The Pelotas (Brazil) 2004 And 2015 Birth Cohorts 

Abstract

Background: In the last decade, there has been an increase in the number of multiple pregnancies. Our aim was to describe the prevalence and duration of multiple pregnancies and compare first- and second-born twins to each other and to singletons, in terms of unfavorable perinatal outcomes and infant mortality rate (IMR). Methods: The 2004 and 2015 Pelotas Birth Cohorts are population-based studies that enrolled all newborns of mothers living in the urban area of Pelotas, South Brazil. All five maternity hospitals in Pelotas were visited daily by the research team, from January 1st to December 31st in 2004 and 2015. A monitoring system was assembled to detect all deaths of cohort participants in the years 2004, 2005, 2015, and 2016. Twinning rate was described according to maternal characteristics (family income, schooling, age, skin color, and morbidity) and parity. First- and second-born twins were compared to each other and to singletons, according to low birthweight (LBW), 5-minute Apgar <7, admission to neonatal intensive care unit (NICU), and IMR:1000 live births (LB). Results: Among 4,187 pregnancies in 2004 and 4,220 in 2015, respectively, 42 (1.0%) and 56 (1.3%) were multiple. Eighty-four twins were born alive in 2004 and 111 in 2015. In the two cohorts, no maternal characteristics were associated with the occurrence of multiple pregnancies. Twin births <34 weeks gestational age more than doubled from 2004 (19.0%) to 2015 (42.1%) (p=0.03). In both cohorts, LBW and admission to the NICU were more frequent in twins than in singletons, with no difference between first- and second-born twins. There was no difference between first-born and second-born twins at the two cohorts nor between twins and single-born infant mortality at the 2004 cohort. Among second-born twins in 2015, the post-neonatal mortality rate was 8 times higher than in singletons (37.7:1,000 LB versus 4.8:1,000 LB), and infant mortality rate (IMR) was 6 times higher (75.4:1,000 LB versus 12.5:1,000 LB). Conclusion: More than one out of 50 births in Pelotas was a twin, generally born prematurely and with a risk six times higher than singletons of dying alongside the first year of life.