title: Factors affecting fetal weight distribution in women with type I diabetes.
abstract: OBJECTIVE
  To identify factors independently affecting fetal weight in women with type I diabetes.
  
  
  METHODS
  Prospectively recorded data in consecutive women with type I diabetes, between 1975-1992.
  
  
  METHODS
  Simpson Memorial Maternity Hospital, Edinburgh. Population Three hundred and two pregnancies with type I diabetes identified before pregnancy, with antenatal care and delivery in the Simpson Memorial Maternity Hospital, a singleton pregnancy, and the same diabetic physician.
  
  
  METHODS
  Normal ranges for birthweight were established for the total hospital population. All cases and the total population had pregnancy dating by ultrasound. The relation between standardised birthweight and explanatory variables was investigated using correlation analysis, t tests and chi2 tests as appropriate, and subsequently using multiple linear regression.
  
  
  RESULTS
  Standardised birthweight in cases, compared with the reference population, showed a unimodal, approximately normal distribution, markedly shifted to the right (mean + 1.26 SD). The most predictive variable was glycated haemoglobin concentration at 27-33 weeks, which explained 6.3% of the birthweight variance, while smoking explained 2.7% and maternal weight 2.0%. There was a trend towards a negative relationship with glycated haemoglobin concentration at 6-12 weeks. Smoking and glycated haemoglobin concentration were strongly intercorrelated.
  
  
  CONCLUSIONS
  Most of the variance in standardised birthweight remains unexplained, but glycated haemoglobin concentration at 27-33 weeks is the most powerful explanatory variable. Possible reasons why there is not a stronger relationship between markers of maternal glycaemia and birthweight are discussed.
authors.affiliation: Simpson Memorial Maternity Pavilion, Edinburgh.
authors.forename: F D
authors.initials: FD
authors.lastname: Johnstone
authors.forename: J H
authors.initials: JH
authors.lastname: Mao
authors.forename: J M
authors.initials: JM
authors.lastname: Steel
authors.forename: R J
authors.initials: RJ
authors.lastname: Prescott
authors.forename: R
authors.initials: R
authors.lastname: Hume
mesh_terms: D001724:Birth Weight / Q000502:physiology*; D003922:Diabetes Mellitus, Type 1; D005260:Female; D020567:Fetal Weight / Q000502:physiology*; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006456:Hemoglobinuria; D006801:Humans; D007003:Hypoglycemia; D007231:Infant, Newborn; D011247:Pregnancy; D011254:Pregnancy in Diabetics; D011446:Prospective Studies; D012307:Risk Factors; D012606:Scotland; D012907:Smoking
chemical_list: D006442:Glycated Hemoglobin