Infant mortality of very preterm infants by mode of delivery, institutional policies and maternal diagnosis.

OBJECTIVE: The aim of this study was to analyse infant mortality among infants born extremely preterm in relation to mode of delivery, maternal diagnosis, and different institutional policies.
METHODS: We conducted a national tertiary health care center study using Swedish Medical Birth Register (MBR) data from 1990 to 2002, to examine the 2,094 live births of infants at 23+0 to 27+6 weeks gestation. We assessed the association between mode of delivery, gestational age (GA), calendar year, maternal condition, and institutional policies on infant mortality outcome.
RESULTS: At 23-25 weeks, 38% of infants (range: 34-69%) were delivered by cesarean section (CS), while at 26-27 weeks, 66% (59-80%) were delivered by CS. The CS rate for fetal or maternal indications was 98% in cases of pre-eclampsia/eclampsia, 42% for premature rupture of membranes (PROM), 68% for hemorrhage, 76% for PROM+hemorrhage, 56% for breech presentation, and 30% for preterm vertex with no other complications. After cases of pre-eclampsia/eclampsia were excluded, vaginal delivery was associated with a small increase of risk for infant death. Vaginal delivery was associated with a significantly increased risk for infant death in breech presentations and multiple births, while vaginal delivery posed a non-significant risk increase for PROM and hemorrhage. For preterm vertex without any other complications, 4 out of 5 infants were delivered vaginally without any risk increase.
CONCLUSION: This study reports high CS rates for very preterm births at Swedish hospitals. In performing CS for very preterm infants, this study suggests a survival advantage for certain maternal conditions, but not for preterm labor with a vertex presentation without other obstetrical complications.