title: Maternal and infant characteristics: differences and similarities between the Nordic countries and the US.
abstract: BACKGROUND
  Data from the Nordic health care registers have been of great value in perinatal epidemiological research. It has been assumed that findings from the Nordic population (Denmark, Finland, Iceland, Norway, and Sweden) are applicable to other populations as well, including the population of the US.
  
  
  OBJECTIVE
  To describe and compare maternal and infant characteristics between the Nordic and the American populations as recorded in the official statistics.
  
  
  METHODS
  This population-based study included data on all females who gave birth and their infants in the Nordic countries and the US. The data were obtained from the US National Center for Health Statistics and the official statistics data for the Nordic countries. The data from all six countries included births from 2006 to 2010.
  
  
  RESULTS
  The mean maternal age at delivery was lower in the US than in the Nordic countries (27.5 vs 30.3 years). Cesarean sections (32.2% vs 17.9%), low birth weight (8.2% vs 4.8%), and preterm birth (12.3% vs 5.9%) were more common in the US than in the Nordic countries. Smoking during early pregnancy was slightly less common in the US compared with Nordic countries (9.8% vs 11.2%). Restricting the data from the US to females with a university degree, characteristics such as age at delivery, birth weight, and preterm deliveries were more in alignment with the Nordic data.
  
  
  CONCLUSIONS
  There are differences in some key maternal and neonatal characteristics between the Nordic countries and the US. However, some characteristics are related to socioeconomic status, suggesting that the Nordic data seem to be applicable to the part of the population in the US with a higher socioeconomic status.
authors.affiliation: Department of Medicine, Solna Centre for Pharmacoepidemiology (CPE), Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Lukas
authors.initials: L
authors.lastname: Löfling
authors.affiliation: Department of Medicine, Solna Centre for Pharmacoepidemiology (CPE), Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Bröms
authors.affiliation: Department of Medicine, Solna Centre for Pharmacoepidemiology (CPE), Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Shahram
authors.initials: S
authors.lastname: Bahmanyar
authors.affiliation: Department of Medicine, Solna Centre for Pharmacoepidemiology (CPE), Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Helle
authors.initials: H
authors.lastname: Kieler
keywords: Nordic countries; US; health care registers; pregnancy