Viability of infants born at 22 to 25 weeks' gestation

To the Editor: A methodologic problem besets the evaluation of the appropriate health care for very premature infants — namely, the unaccounted-for heterogeneity in obstetrical and neonatal care received by these fetuses and infants. Unless this factor is taken into consideration, differences in outcome attributed to gestational age could, in fact, be due to gestational-age-dependent differences in the intensiveness of care. Dr. Allen and her colleagues (Nov. 25 issue)¹ describe gestational-age-determined differences in the intensiveness of obstetrical care offered to fetuses in their cohort. They report that obstetricians tried to avoid performing cesarean sections at 22 to 24 weeks' gestation.