title: Are early first trimester weights valid proxies for preconception weight?
abstract: An accurate estimate of preconception weight is necessary for providing a gestational weight gain range based on the Institute of Medicine's guidelines; however, an accurate and proximal preconception weight is not available for most women. We examined the validity of first trimester weights for estimating preconception body mass index category.
  
  
  
  Under identical measurement conditions, preconception weight and two first trimester weights (i.e., 4-10 and 12 weeks gestation) were obtained (n = 43).
  
  
  
  The 4-10 week and the 12 week weight correctly classified 95 and 91% women, respectively. Mean weight changes were relatively small overall (M = 0.74 ± 1.99 kg at 4-10 weeks and M = 1.02 ± 2.46 at 12 weeks). There was a significant difference in mean weight gain by body mass index category at 4-10 weeks (-0.09 ± 1.86 kg for normal weight participants vs. 1.61 + 1.76 kg for overweight/obese participants, p = 0.01), but not at 12 weeks (0.53 ± 2.29 kg for normal weight participants vs. 1.54 ± 2.58 kg for overweight/obese participants).
  
  
  
  Assigning gestational weight gain guidelines based on an early first trimester weight resulted in 5-9% of women being misclassified depending on the gestational week the weight was obtained. Thus, most women are correctly classified based on a first trimester weight, particularly an early first trimester weight, although it is possible that modeling strategies could be developed to further improve estimates of preconception body mass index category.
  
  
  
  Clinicaltrials.gov # NCT01131117 , registered May 25, 2010.
authors.affiliation: Department of Preventive Medicine, University of Tennessee Health Science Center, 66 N. Pauline St, Memphis, TN, 38163, USA. rkrukows@uthsc.edu.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Krukowski
authors.affiliation: Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia, SC, USA.
authors.forename: Delia S
authors.initials: DS
authors.lastname: West
authors.affiliation: Arkansas Department of Health, Office of Health Communications, Little Rock, AR, USA.
authors.forename: Marisha
authors.initials: M
authors.lastname: DiCarlo
authors.affiliation: Department of Pediatrics, Arkansas Children's Nutrition Center, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
authors.forename: Kartik
authors.initials: K
authors.lastname: Shankar
authors.affiliation: Pediatrics Biostatistics, Arkansas Children's Nutrition Center, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, AR, USA.
authors.forename: Mario A
authors.initials: MA
authors.lastname: Cleves
authors.affiliation: Pediatrics Biostatistics, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, AR, USA.
authors.forename: Marie E
authors.initials: ME
authors.lastname: Saylors
authors.affiliation: Department of Pediatrics, Arkansas Children's Nutrition Center, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
authors.forename: Aline
authors.initials: A
authors.lastname: Andres
mesh_terms: D000328:Adult; D015992:Body Mass Index; D001835:Body Weight; D005260:Female; D005865:Gestational Age; D006801:Humans; D008137:Longitudinal Studies; D015969:National Academies of Science, Engineering, and Medicine, U.S., Health and Medicine Division; D050177:Overweight / Q000150:complications / Q000175:diagnosis; D011237:Predictive Value of Tests; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis / Q000209:etiology; D011261:Pregnancy Trimester, First / Q000502:physiology*; D011295:Prenatal Care / Q000379:methods*; D011296:Prenatal Diagnosis / Q000379:methods*; D012307:Risk Factors; D014481:United States; D015430:Weight Gain
keywords: Obesity; Obstetrics; Preventive medicine