Determinants of fetal haemoglobin in newborn infants.

Percentage fetal haemoglobins (% HbF) were measured in 7081 newborns at the University Hospital, Nottingham, between 1990 and 1992 to assess the effects of a range of factors, and to determine if there was an association between % HbF at birth and risk of SIDS (sudden infant death syndrome). Data from the obstetric clinical records were analysed by multiple linear regression to establish the major determinants of % HbF. New findings were the identification of maternal smoking, twin pregnancy, ethnic origin, and season of birth as significant determinants. Alcohol use, drug and vitamin intake, and duration of labour were not found to be important. The previously reported correlations between % HbF and sex, gestational age, and birthweight were confirmed, and the relative effects quantified. Overall, the major determinants of an increase in % HbF in neonates are similar to the known antenatal risk factors for sudden infant death syndrome (SIDS).