Disparities in pregnancy outcomes according to marital and cohabitation status

Obstet Gynecol. 2004 Jun;103(6):1300-7. doi: 10.1097/01.AOG.0000128070.44805.1f.

Abstract

Objective: To assess the risks and trends of adverse pregnancy outcomes among mothers in common-law unions versus traditional marriage relationships.

Methods: We conducted a birth cohort-based study of all 720,586 births registered in Quebec for the years 1990 to 1997.

Results: The proportion of births to common-law mothers more than doubled from 20% in 1990 to 44% in 1997. Preterm birth, low birth weight, small for gestational age, and neonatal and postneonatal mortality rates increased progressively from mothers legally married, to common-law unions, to lone mothers with father information, to lone mothers without father information on birth registrations. Adjusted odd ratios with 95% confidence intervals (CIs) for common-law versus legally married mothers were 1.14 (95% CI 1.11, 1.17) for preterm birth, 1.21 (95% CI 1.18, 1.25) for low birth weight, 1.18 (95% CI 1.16, 1.20) for small for gestational age, 1.07 (95% 0.97, 1.19) for neonatal death, and 1.23 (95% CI 1.04, 1.44) for postneonatal death after controlled for observed individual- and community-level characteristics. The crude and adjusted odds ratios were virtually unchanged over time.

Conclusion: Pregnancy outcomes are worse among mothers in common-law unions versus traditional marriage relationships but better than among mothers living alone. Modest disparities in pregnancy outcomes in common-law versus traditional marriage relationships have persisted despite the striking rise in common-law unions.

Level of evidence: II-2

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Birth Weight
  • Cohort Studies
  • Female
  • Humans
  • Illegitimacy*
  • Infant, Newborn
  • Longitudinal Studies
  • Marital Status*
  • Marriage / trends
  • Pregnancy
  • Pregnancy Outcome / epidemiology*
  • Quebec / epidemiology
  • Sexual Partners
  • Single Parent
  • Socioeconomic Factors