Limits of viability

Antenatal and Perinatal Management

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 10-15%, and at 24 weeks survival is 50 - 60%. Survival at these ages, however, is accompanied by a high incidence of morbidity.

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 serially.

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 However, after more information is gathered about such an immature infant, support may be withdrawn.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.

Counseling the parents

“The anticipated birth of a neonate at the threshold of viability (25 or fewer completed weeks of gestation) presents a variety of complex medical, social, and ethical concerns.”  The American Academy of Pediatrics and American College of Obstetricians and Gynecologists recommend that obstetric and neonatal health care providers confer regarding the approach to such a delivery, and then counsel the parents consistently and compassionately as to reasonable expectations for the infant’s outcome and care.

Neonatology counseling in anticipation of extreme preterm birth should include the following information:

• A range of the current possible survival rates (preferably institution-specific figures)

• An overview of potential medical problems and their treatment and complications

• The possibility of long-term disabilities, including mental retardation, cerebral palsy, blindness, deafness, and learning disabilities/need for special education

• The possibility that expectations may change after delivery, based on a more accurate assessment of the gestational age and condition of the newborn

• Care should be taken not to include interventions of unproven benefit as “doing everything possible” for the neonate.

The neonatologist counseling the expectant mother of an extremely immature infant should document their discussion either in the mother’s written chart or in the mother’s electronic StarChart.  Documentation should include:

• When the discussion occurred

• Who spoke to whom (include all individuals present)

• Identifying specifics of the particular case and conversation

• The conclusion reached regarding the desires of the family

• Need for ongoing evaluation and discussion as the situation evolves

• Possible reassessment based upon the condition of the infant.

The following graphs and statistics may prove useful in counseling the pregnant mother of a fetus at the threshold of viability.  A handout is available to provide to parents anticipating the birth of an extremely premature infant to assist them in making informed difficult decisions.

National and international survival data were published in Pediatrics, Nov. 2002:

Neonatal Survival/Morbidity by Gestational Age and Birth Weight

Factor                             Mean Survival Rates (%)                    Moderate or Severe Disability (%)

*Too few infants to assess

Vanderbilt’s survival and morbidity statistics from 2001 are similar:

Problems of prematurity include, of course:

• Lung immaturity

• PDA

• Infection

• NEC

• Brain injury

• Inadequate nutrition and growth

• Retinal injury

 These infants have lengthy hospital stays and are generally discharged near their due dates (graphic below is from Stoll, et all for the NICHD-NRN, Pediatrics 2010;126:443–456).

Recently published NICHD data are summarized below (Pediatrics 2005 looking at <25 weeks’ EGA and overall 22-28 weeks’ Pediatrics 2010):

Serious Neonatal Morbidities in Premature Infants 22-28 weeks EGA

Long term problems and handicaps associated with extreme prematurity include:

It is important to remember, and to emphasize to parents, that the chances of survival at any given gestation may vary depending upon that particular infant’s risk factors and clinical condition. Epidemiologic factors including gender, race, and inborn vs. outborn status significantly influence survival. Also, associated medical conditions may worsen odds of survival and prognosis including preterm prolonged premature rupture of membranes, maternal chorioamnionitis, and placental abruption.

Survivors at 23 to 24 weeks’ EGA are more likely to be discharged on oxygen, a monitor, or medications; remain on oxygen or a monitor or require tube feeds beyond the 1st birthday; and have a special health care need (SHCN) at any time than survivors born at 25 to 27 weeks. The strongest predictor of SHCN at discharge is typically BPD/CLD and although rates decrease with increasing age, as many as 40% have persistent SCHN at 18 months (Vohr B, et al: Pediatrics 2010;125:1152–1158).