Placental transfusion strategies in extremely preterm infants: the next piece of the puzzle.

Evidence is growing on the potential value of enhancing placental-fetal transfusion at birth, with recent endorsement of the practice by the World Health Organization and American College of Gynecologists. However, these recommendations provide clinicians with little guidance on the optimal practice among infants born extremely premature (<28 weeks gestation) and those requiring immediate resuscitation. The goals of this review are to: 1) provide rationale for better outcomes among extremely preterm infants following delayed cord clamping or umbilical cord "milking" than with immediate cord clamping; 2) describe clinical situations that warrant immediate cord clamping following delivery and explore the controversy regarding optimal cord clamping practice among extremely premature infants, including those requiring immediate resuscitation; 3) discuss the quality of evidence in this subgroup of infants; 4) consider areas for future research, with a focus on characterizing if placental-fetal transfusion affects the magnitude or timing of variables associated with physiological transition. The review provided herein suggests that delayed cord clamping or umbilical cord milking can be applied safely to infants born prior to 28 weeks gestation, but the lack of evidence on the best practice among infants born severely depressed and requiring immediate resuscitation, who comprise a greater proportion of infant deliveries at the lowest gestational ages, is recognized. Future studies using well-defined physiologic outcome measures are needed to understand the role of placental transfusion in premature infants' adaptations to extrauterine life.