The survival of infants at the limits of viability at Vanderbilt is similar to published national statistics. At 22 weeks (<23 weeks completed gestation) survival is 0%. At 23 weeks gestation survival is 25%, and at 24 weeks survival is 50 - 60%. Obviously, survival at these ages is accompanied by a high incidence of neuro-developmental handicap.

In light of these statistics, Vanderbilt obstetricians and perinatologists do not offer operative deliveries to pregnant women with an estimated gestational age of <24 weeks, except in extreme or unusual circumstances. Continuous electronic fetal monitoring is not indicated at <24 weeks. Instead, auscultation of the fetal heart rate is performed q8 hours.

Neonatology should be consulted to counsel pregnant women if possible prior to the delivery of an infant at 22-25 weeks gestational age. A neonatology fellow or attending should talk to the mother and document their discussion in the maternal chart.

At 22 weeks gestation, no resuscitation will be offered. At 23 weeks gestation, survival is so low and neuro-developmental outcomes so poor that resuscitation is discouraged. At 24 weeks, parents are usually offered evaluation of the infant in the delivery room with resuscitation commenced if the infant is of reasonable size and condition. However, after more information is gathered about such an immature infant, support may need to be withdrawn. Outcomes remain so uncertain for 24 week infants, though, that a parent’s request for comfort measures only should probably not be challenged. At 25 weeks, survival is >75% and neuro-developmental outcomes much improved (albeit not ideal); therefore, resuscitation should be routine for 25 week infants in the delivery room.

Both physicians and parents alike should be cautioned that gestational ages and weights determined by fetal ultrasound are only estimates, and 2 weeks and 200g can make a substantial difference in an extremely preterm infant’s prognosis. Therefore, neonatologists should be present to assess all infants delivered at the limits of viability to confirm estimated gestational age. Parents should be counseled prior to delivery that a resuscitation plan may need to be reconsidered in light of new data once the infant is born. For example, outcomes for incredibly-low-birth-weight infants born without a detectable heart rate are so abysmal that resuscitation should cease in any infant <750g with Apgars of 0¹ and 0⁵.

Reference:

American Academy of Pediatrics. Perinatal care at the threshold of viability. Pediatrics 1995; 96: 974-6.

Allen, MC, et al. The limit of viability-Neonatal outcome of infants born at 22 to 25 weeks gestation. N Engl J Med 1993; 329: 1597-601.

Resolved at Clinical Faculty Quality Improvement Conference 11/12/97 and revisited 1/01.