Evidence of intrapartum hypoxia-ischemia is not present in the majority of cases of neonatal seizures

To determine the extent to which neonatal seizures are associated with intrapartum hypoxia-ischemia. In this case-control study, all neonates diagnosed with seizures at a single institution from 1988 to 1999 were compared to a control group without seizures matched in a 2:1 fashion for gestational age at delivery, birth weight and mode of delivery. Data were abstracted from the maternal and neonatal charts. Parametric variables were compared using an independent samples t test, and non-parametric variables were compared using a Fisher exact test, with p < 0.05 being considered significant. There were 13 cases of neonatal seizures identified, of which one was chromosomally abnormal and excluded from further analysis. For the cases, the mean gestational age at delivery was 34.8 +/- 6.9 weeks, with four preterm and eight term deliveries. The mean birth weight for the cases was 2684 +/- 1369 g (range 590-4350 g). For both cases and controls, 83% were delivered vaginally and 17% by Cesarean section. For term neonates with seizures, the mean length of stay was 11.6 +/- 5.0 days, as compared to 2.5 +/- 0.9 days in the control group (p < 0.001). A 1-min Apgar score of < 7 was found in six of 12 (50%) cases and seven of 24 (29%) controls, and a 5-min Apgar score of < 7 was found in four of 12 (33%) cases and four of 24 (17%) controls (non-significant). In the controls, the mean base excess was -2.8 +/- 2.6 mEq/l, and the mean umbilical arterial pH was 7.28 +/- 0.09. In the case group, two infants born at 24 weeks did not have an umbilical arterial blood gas obtained; in the remaining cases, the mean base excess was -7.6 +/- 6.9 mEq/l (p = 0.02), and the mean cord pH was 7.17 +/- 0.23 (p = 0.065), with only three of ten (30%) having a pH < 7.00 (p = 0.02). Clinically significant acidosis was found in only 30% of neonates who developed seizures, and only one of 12 cases (8%) could possibly have met the criteria of the American College of Obstetricians and Gynecologists for neurological morbidity linked to intrapartum asphyxia. The majority of cases of neonatal seizures were not associated with evidence of intrapartum hypoxia-ischemia.