title: Associations of Early and Late Gestational Weight Gain with Infant Birth Size.
abstract: OBJECTIVE
  Associations of gestational weight gain (GWG) during specific periods of pregnancy with infant birth size have been inconsistent. Infant sex-specific differences in these associations are unknown
  
  
  METHODS
  Information on GWG (kg) [total, early (<20 weeks gestation), and late (≥20 weeks gestation)] and indices of infant birth size including birthweight (BW), ponderal index (PI), crown-heel length (CHL), and head circumference (HC) was collected from 3,621 pregnant women. We calculated adjusted mean differences and 95 % confidence intervals (CIs) relating total, early and late GWG to infant birth size using multivariable linear regression procedures. We used stratified analyses and interaction terms to test whether associations differed by infant sex.
  
  
  RESULTS
  One-kg increases in total, early or late GWG were associated with BW increases of 17.2 g (95 % CI 13.8-18.9), 14.1 g (95 % CI 10.3-18.0), and 21.0 g (95 % CI 16.7-25.4), respectively. Early GWG-BW and late GWG-BW associations were different (p = 0.026). Sex-stratified total GWG-BW associations were similar to overall results. There were sex-specific differences in early GWG-BW and late GWG-BW associations. Among females, early GWG-BW (12.0 g, 95 % CI 6.7-17.2) and late GWG-BW (24.2 g, 95 % CI 18.2-30.3) associations differed (p = 0.0042); the corresponding associations did not differ among males. Total, early, and late GWG were associated with CHL and HC, but not with PI. Associations did not differ for early or late GWG.
  
  
  CONCLUSIONS
  For comparable GWG, late-GWG-related BW increase is greater than early-GWG-related BW increase, particularly among female infants.
authors.affiliation: Department of Epidemiology, University of Washington, 1730 Minor Avenue, Suite 1360, Box 358085, Seattle, WA, 98101, USA. lwander@u.washington.edu.|Department of Medicine, University of Washington, Seattle, WA, USA. lwander@u.washington.edu.
authors.forename: Pandora L
authors.initials: PL
authors.lastname: Wander
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA, USA.
authors.forename: Colleen M
authors.initials: CM
authors.lastname: Sitlani
authors.affiliation: Department of Epidemiology, University of Washington, 1730 Minor Avenue, Suite 1360, Box 358085, Seattle, WA, 98101, USA.
authors.forename: Sylvia E
authors.initials: SE
authors.lastname: Badon
authors.affiliation: Department of Epidemiology, University of Washington, 1730 Minor Avenue, Suite 1360, Box 358085, Seattle, WA, 98101, USA.|Department of Medicine, University of Washington, Seattle, WA, USA.|New York Academy of Medicine, New York, NY, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Siscovick
authors.affiliation: Department of Epidemiology, Harvard University, Boston, MA, USA.
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Williams
authors.affiliation: Department of Epidemiology, University of Washington, 1730 Minor Avenue, Suite 1360, Box 358085, Seattle, WA, 98101, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Enquobahrie
mesh_terms: D000328:Adult; D001724:Birth Weight / Q000502:physiology*; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology*; D005260:Female; D047109:Fetal Development; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D017533:Marital Status; D008423:Maternal Age; D011247:Pregnancy / Q000706:statistics & numerical data*; D011248:Pregnancy Complications; D011264:Pregnancy Trimesters; D011446:Prospective Studies; D013997:Time Factors; D014861:Washington; D015430:Weight Gain / Q000502:physiology*; D055815:Young Adult
keywords: Birth weight; Fetal growth; Gestational weight gain; Infant sex