Data on morbidity and mortality of very premature infants are largely based on studies conducted before the extensive use of steroids and surfactant, and other innovations that have significantly improved the prognosis of these infants. Kilpatrick and colleagues reviewed data on infants born at 24 to 26 weeks of gestation to assess rates of mortality and morbidity in these infants.
The authors identified 138 infants born between 1990 and 1994 from obstetric records and used early examination or ultrasonic estimation as measures of gestational age. Patients who underwent termination of pregnancy or had intrauterine fetal demise were excluded from the study. Infants with severe congenital anomalies were also excluded from the estimations of mortality and morbidity. During the study period, antenatal steroids were used routinely, and surfactant was given to all infants born before 27 weeks of gestation.
Spontaneous preterm labor was the cause of delivery in 54 of the 138 infants (39 percent). In the remaining cases, premature birth was attributed to premature rupture of membranes, preeclampsia, abruption or placenta previa. Seven infants were stillborn and three of those born at 24 weeks of gestation were not resuscitated. Eighteen of the infants born at 24 weeks (43 percent), 31 of those born at 25 weeks (74 percent) and 45 infants born at 26 weeks (83 percent) survived.
One third of the infants born at 24 weeks of gestation had severe retinopathy or chronic lung disease, but this incidence decreased by about one half for every additional week gained in utero. Only two of the infants born at 26 weeks of gestation had severe retinopathy, and three had chronic lung disease. The mean duration of hospital stay for infants born at 24 weeks of gestation was 4.0 months, compared with 2.9 months for the infants born at 25 weeks of gestation and 2.7 months for infants born at 26 weeks of gestation. The cost per survivor was calculated to be $294,749 for infants born at 24 weeks of gestation, $181,062 for those born at 25 weeks and $166,215 for those born at 26 weeks.
In a related article, Piecuch and colleagues report on the one-year follow-up of 86 infants born at 24, 25 or 26 weeks of gestation. The incidence of cerebral palsy was similar in all three groups: two of 18 infants born at 24 weeks of gestation (11 percent), six of 30 infants who were born at 25 weeks (20 percent) and four of 38 infants who were born at 26 weeks (11 percent).
Cognitive development was strongly related to gestational age. Five of the infants born at 24 weeks of gestation (28 percent) had normal cognitive development. Fourteen of the infants born at 25 weeks (47 percent) and 27 of the infants born at 26 weeks (71 percent) had normal cognitive development. Cognitive outcome showed a significant relationship with four risk factors: chronic lung disease, intracranial hemorrhage or periventricular leuko-malacia, substance abuse and high social risk.
The percentage of infants who were neurologically normal also was related to gestational age. Twelve of the infants born at 24 weeks (67 percent) demonstrated normal neurologic outcome, compared with 22 of the infants born at 25 weeks (73 percent) and 34 of the infants born at 26 weeks (89 percent). Poor neurologic outcome correlated with grade 3 or grade 4 intracranial hemorrhage or periventricular leukomalacia. It did not correlate with chronic lung disease, sex of the infant, substance abuse or high social risk.
The authors calculate that the chances of an infant having normal or borderline-normal cognitive outcome is 26 percent in those born at 24 weeks of gestation, 52 percent at 25 weeks and 74 percent at 26 weeks.