Associations between features of placental morphology and birth weight in dichorionic twins

Alexa A. Freedman, Carol J. Hogue, Carmen J. Marsit, Augustine Rajakumar, Alicia K. Smith, Katherine L. Grantz, Robert L. Goldenberg, Donald J. Dudley, George R. Saade, Robert M. Silver, Karen J. Gibbins, Radek Bukowski, Carolyn Drews-Botsch

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Low birth weight is associated with perinatal and long-term morbidity and mortality, and may be a result of abnormal placental development and function. In studies of singletons, associations have been reported between features of placental morphology and birth weight. Evaluating similar associations within twin pairs offers a unique opportunity to control for key confounders shared within a twin pair, including gestational age, parental characteristics, and intrauterine environment. Data from 3 studies in the United States that were completed from 2012 to 2013, 2006 to 2008, and 1959 to 1966 were used in our analysis of 208 sets of dichorionic twins with unfused placentas. We used linear regression to model difference in birth weight within a twin pair as a function of differences in placental characteristics (i.e., thickness, 2-dimensional surface area, intraplacental difference in diameter). After controlling for sex discordance, a 75.3- cm2 difference in placental surface area, which reflects the interquartile range, was associated with a difference in birth weight of 142.1 g (95% confidence interval (CI): 62.9, 221.3). The magnitude of the association also may be larger for same-sex male pairs than same-sex female pairs (males: 265.8 g, 95% CI: 60.8, 470.8; females: 133.0 g, 95% CI: 15.7, 250.3). Strong associations between surface area and birth weight are consistent with reported results for singleton pregnancies.

Original languageEnglish (US)
Pages (from-to)518-526
Number of pages9
JournalAmerican journal of epidemiology
Issue number3
StatePublished - Mar 1 2019
Externally publishedYes


  • Birth weight
  • Placenta
  • Twins

ASJC Scopus subject areas

  • Epidemiology


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