“Umbilical blood flow is complex,” he said. Blood flows toward the baby via the umbilical vein during inhalation, but stops or reverses during crying. The umbilical artery primarily carries blood to the placenta, and flow stops after about 4 minutes in more than half of infants. Gravity’s role in blood flow is controversial (Lancet. 2014 Jul 19;384[9939]:235-40).
The two options for placental transfusion are delayed cord clamping and milking the umbilical cord (also called “stripping”). In vaginal births, delayed clamping allows 20 mL/kg blood to transfer to the baby by 3 minutes after birth, with 90% of that reaching the baby in the first minute (Lancet. 1969 Oct 25;294[7626]:871-3).
Blood transfer is less efficient in cesarean births, so milking may be more efficient than simply delaying clamping, according to a small randomized controlled trial of preterm infants around 28 weeks’ gestational age. No difference between the methods was seen in vaginal births. To milk the cord, pinch it near the placenta and squeeze it toward the newborn for 2 seconds; then release, refill and repeat.
The biggest benefits in delayed cord clamping or milking occur among preterm infants: decreased mortality, higher mean arterial pressure on day 1, and a lower risk of blood transfusion, necrotizing enterocolitis, and a Bayley Motor score below 85 at 18-22 months. Term babies also get benefits, though: increased hemoglobin at birth (approximately 2 g/dL), a 0.5- to 5-point average increase in boys’ Ages & Stages fine motor and social domain scores at age 4 years, and among high-risk infants, a lower risk of iron deficiency anemia at age 1 year (JAMA Pediatr. 2017;171[3]:264-70).
According to current guidelines from the American Academy of Pediatrics, “delayed cord clamping longer than 30 seconds is reasonable for both term and preterm infants who do not require resuscitation at birth,” but “there is insufficient evidence to recommend an approach to cord clamping for infants who require resuscitation.” They also recommend against routine milking for newborns less than 29 weeks’ gestation (Pediatrics. 2015 Nov;136 Suppl 2:S196-218).
Meconium-related complications
Meconium-stained amniotic fluid (MSAF) is common, occurring in about 8% of deliveries and increasing with gestational age, but meconium aspiration syndrome (MAS) is less common, occurring in about 2% of all MSAF cases (Int J Pediatr. 2012. doi: 10.1155/2012/321545).
Risk factors for severe MAS include thick meconium and an abnormal fetal heart rate. But about two-thirds of MAS cases are mild, not requiring ventilation or continuous positive airway pressure (CPAP), Dr. Weiner said. Practice should be driven by evidence from randomized controlled trials (RCTs).
“Nonrandomized observational studies can be misleading, and rational conjecture has led to many mistakes in medicine,” he said. “Be willing to challenge conventional wisdom.” For example, the standard of care in the 1970s, based on two nonrandomized retrospective reviews of 175 babies, included orapharyngeal and nasopharyngeal suction by the obstetrician and endotracheal tube (ETT) suction by the pediatrician. In the 2000s, however, an RCT of 2,500 infants found no benefit from orapharyngeal and nasopharyngeal suction, even with thick MSAF, (Lancet. 2004 Aug 14-20;364[9434]:597-602) and another RCT with 2,100 infants found no benefit from ETT suction (Pediatrics. 2000 Jan;105[1 Pt 1]:1-7).
More recent, smaller studies have confirmed those conclusions and found similar lack of benefit from ETT in non-vigorous infants, contributing to the new recommendation (Resuscitation. 2016 Aug;105:79-84Indian J Pediatr. 2016 Oct;83[10]:1125-30).
“Routine tracheal suction is no longer recommended for nonvigorous babies with meconium stained fluid,” Dr. Weiner said. Since MSAF is risk factor for resuscitation, though, at least two clinicians with Neonatal Resuscitation Program (NRP) training should be present, as well as a full team if resuscitation is expected.
Heart rate assessment and tracking
“The baby’s heart rate needs to be monitored during PPV [positive pressure ventilation] because a prompt increase in the baby’s heart rate is the most important indicator of effective PPV,” Dr. Weiner said in an interview. “Half of errors made during NRP [Neonatal Resuscitation Program] simulations are the result of incorrect heart rate assessment.”
Recent evidence comparing pulse oximetry to an EC monitor favored the latter for tracking heart rate, leading to the other new recommendation.
“The baby’s heart rate can be monitored using the pulse oximeter,” Dr. Weiner said. “However, health providers should consider using an electronic cardiac monitor in addition to pulse oximetry because studies show that it achieves a reliable signal faster.” He cited a study of 20 newborns that showed an EC monitor determined the heart rate in a median 34 seconds, compared with 122 seconds with the pulse oximeter (Pediatr Int. 2012 Apr;54[2]:205-7).
Pulse oximetry takes 90-120 seconds to attain a reliable signal and may not work if there’s poor perfusion, but an EC monitor provides continuous heart rate monitoring even with poor perfusion. So an initial heart rate assessment by auscultation is fine, but if PPV begins, EC monitoring may be better and is the preferred method with anticipated resuscitation or chest compressions.
However, pulse oximetry is still recommended “whenever positive pressure ventilation is started or oxygen is administered in order to guide the appropriate amount of oxygen supplementation,” Dr. Weiner noted.
He added that “preliminary studies suggest that handheld Doppler fetal heart monitors correlate well with ECG, provide a rapid audible heart rate and may be a promising alternative in the future” (Pediatr Int. 2017 Oct;59[10]:1069-73).
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