Risk factors for asphyxia associated with substandard care during labor. 
To identify maternal, pregnancy, delivery and infants characteristics related to neonatal asphyxia and associated with substandard care.  A nation-wide case-control study in Sweden.  Infants born between 1990 and 2005 with a gestational age > or = 33 weeks and a spontaneous or induced onset of labor.  Cases were 177 previously identified infants suffering from encephalopathy caused by asphyxia where there was suspected substandard care during labor, and where claims for financial compensation were filed.  Controls were identified from the population-based Swedish Medical Birth Register, had an Apgar score of 10 at five minutes, and were alive at 28 days of age.  Severe asphyxia associated with substandard care during childbirth.  Maternal and delivery factors associated with asphyxia included maternal age > or = 30 years, short maternal stature (< or =159 cm), previous cesarean delivery, insulin-dependent diabetes before pregnancy and gestational diabetes, induced deliveries and delivery at night, with adjusted odds ratios (ORs) ranging from a two- to fourfold increase in risk.  Compared with non-dystocic deliveries, the OR for dystocic deliveries was fivefold higher, and was further increased if epidural anesthesia or opioids were used.  Small- and large-for-gestational age infants, post-term (> or =42 weeks) births, twins and breech deliveries had a three- to eightfold increase in risk of asphyxia when there was substandard care during labor.  Dystocia of labor, especially if epidurals and/or opioids are used, is the strongest risk factor associated with substandard care causing severe asphyxia during labor.