title: Variation in newborn size according to pregnancy weight change by trimester.
abstract: BACKGROUND
  The timing of maternal weight change in pregnancy may be an important determinant of the newborn's size.
  
  
  OBJECTIVE
  The purpose was to identify effects of maternal weight change by trimester on newborn size, under the hypothesis that low weight gain early in pregnancy predicts proportionately smaller newborns.
  
  
  METHODS
  Women planning to become pregnant were followed by clinic visits and questionnaires through delivery. This study includes 389 women and their singleton infants born at a gestational age of > or = 241 d.
  
  
  RESULTS
  In multiple regression analyses including a variety of potential confounders, maternal weight gain in the first and second trimesters predicted newborn weight (1-kg weight gain in the first trimester predicted a 31-g increase in newborn weight, P < 0.0007, and 1-kg weight gain in the second trimester predicted a 26-g increase in newborn weight, P < 0.007), but weight gain in the third trimester did not. Newborn ponderal index (in kg/m(3)) was predicted by weight gain in the first (1-kg weight gain predicted an added 0.21 units, P < 0.0003) and third (1-kg weight gain predicted an added 0.12 units, P < 0.03) trimesters but not in the second trimester. Newborn weight was 211 g lower (P < 0.006) and ponderal index 1.2 units lower (P < 0.02) in infants born to women who lost weight in the first trimester.
  
  
  CONCLUSIONS
  The use of measured prepregnancy weight in tests of the effect on newborn size of weight gain by time in pregnancy produces different results than does the use of recalled prepregnancy weight. Maternal weight change in the first trimester of pregnancy more strongly influences newborn size than does weight change in the second or third trimester.
authors.affiliation: Department of Public Health Nutrition, School of Public Health, University of Minnesota, Minneapolis 55454-1015, USA. brown_j@epi.umn.edu
authors.forename: Judith E
authors.initials: JE
authors.lastname: Brown
authors.forename: Maureen A
authors.initials: MA
authors.lastname: Murtaugh
authors.forename: David R
authors.initials: DR
authors.lastname: Jacobs
authors.forename: Helen C
authors.initials: HC
authors.lastname: Margellos
mesh_terms: D000328:Adult; D001724:Birth Weight; D015992:Body Mass Index; D005314:Embryonic and Fetal Development; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011248:Pregnancy Complications; D011264:Pregnancy Trimesters; D011446:Prospective Studies; D012044:Regression Analysis; D015430:Weight Gain