Prenatal and intrapartum events and sudden infant death syndrome. 
The purpose of this study was to evaluate specific pregnancy and labour and delivery events that may increase the risk of sudden infant death syndrome (SIDS).  A matched case-control study was conducted in five counties in southern California, using California death certificate records.  The sample consisted of 239 Caucasian, African-American, Hispanic and Asian mothers of SIDS infants and 239 mothers of control infants matched on sex, race, birth hospital and date of birth.  Mothers participated in a detailed telephone interview and provided access to obstetric and paediatric records.  More case than control mothers reported a family history of anaemia (OR=2.12, P < 0.001).  Placental abruptions were strongly associated with SIDS (unadjusted OR=7.94, [95% CI 1.34,47.12]).  There was an increased risk of SIDS death associated with maternal anaemia during pregnancy (OR=2.51, [95% CI 1.25,5.03]), while simultaneously adjusting for maternal smoking during pregnancy, maternal years of education and age, parity, infant birthweight, gestational age, medical conditions at birth, infant sleep position and post-natal smoking.  Interactions of anaemia and prenatal smoking as well as anaemia and post-natal smoking were not statistically significant.  There were no other statistically significant differences between case and control mothers for pregnancy conditions, labour and delivery events (e.g. caesarean sections, anaesthesia, forceps) or newborn complications (e.g. nuchal cord, meconium aspiration).  Anaemia and placental abruptions were significantly associated with an increased risk of SIDS; both are circumstances in which a fetus may become hypoxic, thereby compromising the subsequent growth, development and ultimate survival of the infant.