A narrative review of delaying cord clamping 2020—who, what, when, where, why and how?

Abstract

: Delayed cord clamping (DCC) facilitates transfusion benefit for infants with spontaneous ventilation. Visibly apneic infants with normal heart rate and cardiac output, while still connected to intact placental circulation are capable of oxygenation and ventilation through the placental fetal-maternal respiratory membrane as they achieve normal perinatal cardiorespiratory and hemodynamic transition, and optimal mother-infant bonding. We aim to describe recent human physiology studies during DCC and implications for clinical practice. The risks of maternal hemorrhage and/or interruption of fetoplacental gas exchange due to premature and occult placental separation prior to establishment of this transition, occur in ~10% of deliveries. These risks must be carefully adjudicated as we seek to provide benefit to the majority (~90%) of infants at birth. Recognizing risk to the mother or infant peri-partum is critical to distinguishing these two groups, resulting in inability to provide DCC, or truncating its intended duration. This narrative review focuses on optimal placental transfusion duration, increased infant iron stores, improved early brain myelination and long-term neurodevelopmental advantage. Term infants with five minutes of DCC show ~100g birthweight increase, presumably the weight of additional transfused blood. Extremely preterm infants (<28–29 weeks gestation) or extremely low birth weight (ELBW) (<1,000 g) neonates, optimally prepared (with antenatal steroids and infant neuro-protective magnesium sulfate) have survival advantage, improved euthermia, less likelihood of intubation in the delivery room (DR) and/or during hospitalization, improved hematocrit, less transfusion risk and enhanced iron transfer. Improved iron transfer results in optimal infant brain myelination, a putative mechanism for neurodevelopmental functional enhancement. Optimal DCC duration is unknown but 2–5 minutes is likely safe and effective for most infants (being not feasible in all) and probably of greatest benefit to the least mature, without adversely affecting cord blood gases at birth, nor increasing maternal risk of postpartum hemorrhage. Absolute contraindications for DCC include perinatal sentinel events such as premature placental separation, cord prolapse, uterine rupture and certain maternal life-threatening events. Relative contraindications include prolonged infant apnea. Truncation of intended DCC duration is appropriate if infant cardiac output and/or utero-placental integrity are not reassuring.