THE LIMIT OF VIABILITY - NEONATAL OUTCOME OF INFANTS BORN AT 22-WEEKSTO 25-WEEKS GESTATION

Background. With improved survival of preterm infants, questions have been raised about the limit of viability. To provide better informatio n and counseling for parents of infants about to be delivered after 22 to 25 weeks' gestation, we evaluated the mortality and neonatal morbi dity of preterm infants born at these gestational ages. Methods. We st udied retrospectively all 142 infants born at 22 to 25 weeks' gestatio n (as judged by best obstetrical estimate) from May 1988 through Septe mber 1991 in a single hospital. Mortality in the first six months, inc luding stillbirths, and neonatal morbidity (i.e., the presence of intr acranial pathologic conditions, chronic lung disease, and retinopathy of prematurity) were analyzed. Results. Fifty-six infants (39 percent) survived for six months. Survival improved with increasing gestationa l age; none of 29 infants born at 22 weeks' gestation survived, as com pared with 6 of 40 (15 percent) born at 23 weeks, 19 of 34 (56 percent ) born at 24 weeks, and 31 of 39 (79 percent) born at 25 weeks. There were seven stillbirths at 22 weeks' gestation and four stillbirths at 23 weeks. The more immature the infant, the higher the incidence of ne onatal complications as determined by the number of days of mechanical ventilation, the length of the hospital stay, and the presence of ret inopathy of prematurity, periventricular or intraventricular hemorrhag e, or periventricular leukomalacia. Only 2 percent of infants born at 23 weeks' gestation survived without severe abnormalities on cranial u ltrasonography, as compared with 21 percent of those born at 24 weeks and 69 percent of those born at 25 weeks. Conclusions. We believe that aggressive resuscitation of infants born at 25 weeks' gestation is in dicated, but not of those born at 22 weeks. Whether the occasional chi ld who is born at 23 or 24 weeks' gestation and does well justifies th e considerable mortality and morbidity of the majority is a question t hat should be discussed by parents, health care providers, and society .