Placental Transfusion in the Newborn

KEY POINTS

• 1.

  Delayed cord clamping (DCC) is a very powerful yet simple, no-cost intervention practice that can transform the lives of children and mothers around the world.

• 2.

  DCC is a practice of waiting to cut the umbilical cord until sufficient time (3–5 minutes) has elapsed to permit blood flow from the placenta to the newborn while the baby is transitioning to extrauterine life.

• 3.

  DCC facilitates placental transfusion and maintains systemic cardiac output until the newborn lungs establish lung circulation with the initiation of spontaneous breathing.

• 4.

  Placental transfusion can also be accomplished by umbilical cord milking or cord milking through an intact umbilical cord.

• 5.

  Placental transfusion volume to the newborn depends on the time to clamp the cord after birth, the position of the newborn relative to the location of the placenta, placental contractions, and the onset of spontaneous breathing in the newborn.

• 6.

  DCC is an easily implemented intervention that requires joint cooperation among healthcare providers involved in childbirth and a participatory culture change in public health.

• 7.

  Major benefits of DCC include improved cardiopulmonary transition, improved survival rates with reduced hospital mortality for preterm infants, reduction in iron-deficiency anemia in term infants during the first year of life through improved iron stores, and positive impact on neurodevelopment at 4 years of age.

Introduction

The transition from fetal to newborn life is characterized by both initiation of spontaneous breathing and changes to circulation. Delayed cord clamping (DCC) is a practice of waiting to cut the umbilical cord until sufficient time (3–5 minutes) has elapsed to permit blood flow from the placenta to the newborn while the baby is transitioning to extrauterine life. DCC facilitates placental transfusion, or the transfer of warm oxygenated blood from the placenta to the newborn at a slow rate, facilitated by uterine contraction. ^, DCC permits placental transfusion, and a passive transfer of stem cells, antibodies, and iron-rich blood from the placenta to the newborn occurs. DCC has enormous proven benefits for both premature and term infants. In the preterm infant, DCC assists with improved cardiopulmonary transition with stable blood pressures, reduction in intraventricular hemorrhages (IVH), reduced infection rates, reduced use of blood products in the neonatal intensive care unit, and improved survival rates. In the term infant, DCC is associated with reduction of both iron-deficiency anemia and improved neurodevelopmental outcomes at 4 years of age.

DCC is an age-old practice that has shifted to immediate clamping during the decades since the 1950s without conducting randomized controlled trials on this change. ^, Currently, the umbilical cord is clamped early, from immediately to within 15 seconds of birth, while there is still a significant circulation occurring through the umbilical vessels. The newborn is then quickly transferred to the pediatric provider in an effort to avoid delayed resuscitation. Immediate clamping of the cord is both a nonphysiologic and avoidable intervention that abruptly interrupts the natural process of placental transfusion. Immediate cord clamping prevents acquisition of adequate blood volume and thus may cause more harm than benefit to the baby. Reports from a systematic review and meta-analysis of delayed versus early umbilical cord clamping for preterm infants report a 28% to 30% increase in hospital deaths for preterm infants who had their cords clamped immediately after birth. ^,

It has been reported that 80 to 100 mL of blood transfers from the placenta in the first 3 minutes after birth. ^{, ,} Clamping the umbilical cord while significant circulation is still occurring through the umbilical vessels drops the cardiac output by approximately 40%. This deprives the newborn of the benefit of added circulating blood volume (up to 100 mL) from continuing placental transfusion. Sick and preterm infants are especially likely to benefit from the additional blood volume achieved by DCC, besides term infants. ^{, ,} Despite endorsements for DCC by numerous governing bodies and stakeholders ( Table 7.1 ) including the International Federation of Gynaecology and Obstetrics (2003), European Confederation of Midwives (2003), Society of Obstetricians and Gynaecologists of Canada (2009, 2016), International Liaison Committee on Resuscitation (2010, 2015), International Consensus on Cardiopulmonary Resuscitation (2011), World Health Organization (2014), National Institute for Health and Care Excellence (NICE) of the United Kingdom (2015), Royal College of Obstetricians and Gynaecologists (2016), Textbook of Neonatal Resuscitation , 7th edition (2016), Helping Babies Breathe, 2nd edition (2016), American Academy of Pediatrics (2017), American College of Obstetricians and Gynecologists (2017), and European Association of Perinatal Medicine, the practice of DCC has been slow to be adopted.

Pathophysiology of Placental Transfusion

In the fetus, the lungs are filled with fluid. No gas exchange occurs, and this results in approximately 15% of the right ventricular cardiac output entering the fetal lungs. The oxygenated umbilical venous blood from the placenta that enters the right atrium is shunted across the foramen ovale to enter the left atrium. This serves as a preload for the left ventricle to supply oxygenated blood to the head and neck vessels. The umbilical venous blood that enters the right ventricle and pulmonary artery is then shunted across the ductus arteriosus to supply the rest of the body tissues. However, soon after birth, when the baby initiates breathing, the lungs are filled with air that assists with the drop in pulmonary vascular resistance and increases blood flowing into the pulmonary circulation. Thereafter, blood returns to the left ventricle to maintain systemic cardiac output. The newly accelerated pulmonary blood flow now replaces the umbilical venous blood as the source of the preload. This results in improved left ventricular output and systemic blood flow.

Clamping the umbilical cord resulted in a drop of right ventricular output and thereafter the systemic cardiac output in preterm lamb studies. If immediate clamping of the umbilical cord is performed before breathing is established, this blocks the acquisition of added blood volume from the placenta. This results in hypovolemia in a newborn, especially when compromised by asphyxia. Experimental studies in preterm lambs have shown positive effects for both systemic and cerebral hemodynamic parameters, including oxygen saturation when respiratory support is initiated prior to clamping the umbilical cord. The drop in right ventricular output is mitigated when the cord is clamped after breathing is established. The umbilical venous blood now serves as a source of left ventricular preload until the pulmonary venous return is established with breathing and systemic blood flow is thereafter maintained.

Thus establishing lung inflation and pulmonary circulation through effective breathing prior to the clamping of the umbilical cord could lead to smoother cardiovascular transition and reduce the risk of IVH. Therefore placental transfusion is an effective method of enhancing arterial oxygen content from the additional blood volume, maintaining cardiac output and increasing oxygen delivery during the transition period while the baby is attempting to establish breathing and pulmonary circulation. In addition, placental transfusion has been associated with lower incidences of sepsis and necrotizing enterocolitis in preterm infants. Placental blood remains an untapped physiologic reservoir of hematopoietic and pluripotent stem cell lines.

Factors That Determine Placental Transfusion

Several important factors determine the volume of residual placental blood that is transferred to the neonate ( Fig. 7.1 ). They are as follows.