[Birth asphyxia and hypoxic ischemic encephalopathy, incidence and obstetric risk factors]

Modern medical practice has changed dramatically during the past decades because of improved technology. Still, fetal surveillance during labor is relatively unchanged since 1960 s when fetal heart rate monitoring (FHR) became standard practice. Newborn infants are still suffering from birth asphyxia and in severe cases leading to hypoxic ischemic encephalopathy (HIE) which sometimes results in permanent neurological damage. The incidence of birth asphyxia and HIE in Iceland is unknown and so are the risk factors for severe asphyxia. The objective of this study was to assess the incidence, obstetric risk factors and the sequela of severe asphyxia at Landspitali university hospital (LSH).

All term infants born at LSH from 1.1.1997- 31.12.2001 with birth asphyxia, defined as five minute Apgar score %lt;6, were included in the study (n=127). Clinical information were collected retrospectively from maternal records on maternal diseases during pregnancy, cardiotocogram (CTG), type of birth, the presence of meconium and operative delivery rates. Information was also collected regarding birth asphyxia and HIE in the neonatal period.

The incidence of birth asphyxia was 9.4/1000 live term births during the study period, with increasing incidence during the three last years. The incidence of HIE was 1.4/ 1,000 live term births. Severe maternal diseases during pregnancy were not a significant risk factor for asphyxia. The amniotic fluid was meconium stained in fifty percent of cases and the umbilical cord was wrapped around the fetal neck in 41% of cases. Abnormal CTG tracing was observed in 66% of cases in the study group and in 79% of the HIE cases. Operative deliveries were significantly more common in the study cohort compared with other deliveries at LSH at the same time: ventouse delivery 22% vs 6.8% (p<0,001), forceps delivery 6.3% vs 1,03% (p<0,001), emergency cesarean section 19.7% vs 11.4% ( p=0,008).

The incidence of birth asphyxia is higher in LSH compared with the incidence found in other studies. Signs of fetal distress on CTG and delivery with operative interventions are common. With current available methods to detect intrapartum asphyxia there is a poor correlation with CTG and the development of HIE after severe asphyxia. The presence of severe maternal diseases does not correlate with increased incidence of asphyxia, presumably due to increased surveillance of these pregnancies and a lower treshold for intervention during delivery. In low risk pregnancies there is a lack of appropriate methods with high sensitivity and specificity to detect intrapartum asphyxia.