Guest post by IBMS student Savanna Barcus
Physiological Cord Clamping
As our 17-year-old moved out of the home this very week, my husband reassured me that it was time to cut the cord. I lamented that we cut the cord a long time ago, but it was probably too soon even then! In researching cord clamping I have narrowed down the ideal cord clamping time to somewhere between when a child is born, to when the child turns into a young adult and leaves the home. A more specific time than that has been the center of much debate over the last few centuries. I propose that time isn’t what we should be measuring when deciding when to clamp and cut the umbilical cord, but we should be looking at the baby for physiological signs that the newborn is ready.
Starting in the 17th century with male midwives attending deliveries women began delivering lying down in bed. This positional change made it more difficult for the placenta to spontaneously deliver, necessitating cutting the cord and manually removing the placenta. The practice of clamping and cutting the cord continued to grow in popularity over the centuries. Other thoughts on why cord clamping became the norm; to avoid blood loss from the baby, the clamp made it easy to determine when the cord lengthened indicating the placenta had separated and was ready for manual removal, and to keep the bedding clean by not allowing placental blood to leak out of the cut cord.
Interestingly in 1801 Erasmus Darwin, grandfather of Charles Darwin, wrote that “Another thing very injurious to the child is the tying and cutting of the navel string too soon: which should always be left til the child has not only repeatedly breathed, but till all pulsation in the cord ceases. As otherwise the child is much weaker than it ought to be; a part of the blood being left in the placenta, which ought to have been in the child.” Educated men of the time recognized the value of not clamping and cutting the cord, and even recognized physiological signs indicating time for the cord to be clamped. How did we stray so far from respecting and allowing the physiological process to be carried out the way nature intended?
There have been many misconceptions over cord clamping, with good intentions, which has led to the common practice of immediately clamping the cord. Early in the 20th century more scientific reasons for cord clamping were realized. One being RH blood type incompatibilities were understood to be the cause of hemolytic disease of the newborn. By clamping the cord early, excessive amounts of maternal blood were prevented from entering the newborn. However, in the 1960’s RH Immune Globulin and testing of blood types removed the need for early cord clamping. Twilight sleep and the use of intravenous and intramuscular pain medications in labor became another reason to clamp immediately. A newborn with respiratory depression due to maternal narcotics needs the cord clamped immediately to stop the transfer of medication and begin respiratory resuscitation. Better understanding of maternal fetal transfer of medications has led to safer use of pain medications such as not giving IV narcotics near time of delivery. Currently epidurals are the primary method of pain control utilized in the United States. This allows very little transfer of medication to the infant. Other concerns were increased risk of jaundice due to excessive blood cells from prolonged clamping. In a 2017 study Cernadas however, found that there were no differences observed between groups of immediate, 1 minute, and 3 minute cord clamping in terms of bilirubin levels and indication for phototherapy. Winkler also confirmed this in their 2022 study stating that concerns around the need for phototherapy in relation to delayed cord clamping can be abandoned.
Now that we have dispelled the common myths around need for immediate cord clamping let’s turn and look at the benefits of delayed cord clamping The recent 2022 study by Winkler found that delaying cord clamping for 3-5 minutes in term infants allowed them to receive a placental transfusion of 25%-35% of their total blood volume. This would amount to 80-100ml of blood according to Cernadas. Benefits of receiving the full amount of placental blood destined for the newborns circulation includes improved oxygenation immediately after birth, reducing the risk of iron deficiency in the infant at 3-8 months of age, improving neurodevelopment at 12 and 48 months, and improving brain myelin content during infancy (Winkler, 2022). In preterm infants this reduces mortality by approximately 30% (Winkler, 2022). Along with increasing the newborn’s total blood volume come stem cells, and other protective components of blood cells (erythrocyte, catalase, superoxide dismutase, tumor necrosis factor receptor 2 and more) which offer protection against free radicals and oxidative stress (Cernadas 2017). Winkler also determined that maternal postpartum blood loss was reduced with delayed cord clamping, and that delaying cord clamping beyond 3 minutes was not associated with any negative consequences for the mother or baby.
Understanding the myths, and now the benefits we can go back to our original questions, when is the ideal time to clamp the cord? In 2016 Hooper et al. published a study stating that the most dominant factors in umbilical cord clamp timing are lung aeration, spontaneous inspirations, crying, and uterine contractions. Hooper concluded that the timing of umbilical cord clamping should be based on the infant’s physiology rather than a stopwatch. In particular whether the infant is breathing or not. Aerating the lungs is the catalyst for the infant to switch from umbilical blood flow (mothers’ placenta) as the primary source of oxygenation to pulmonary blood flow within their own lungs. If the cord is cut prior to the infant breathing spontaneously, and blood has not yet been directed to the circulation around the lungs, then the infant is born with a deficit of blood. Given this understanding, it is clear that routine practices such as immediate cord clamping and even clamping and cutting the cord to allow for resuscitation of the newborn needs to be re-evaluated in order to support the physiological process of newborn transition with an intact cord.
Humans like routine, and time may be an easier marker for birth attendants to monitor, but as we have learned time isn’t the most important factor in deciding when to clamp and cut the cord, if at all. Monitoring the infant for the first breaths and cries, palpating the cord for pulse, and observing signs such as the cord becoming limp and pale are the signs we should be looking for to know when to clamp and cut the cord, if the parent is ready. As far as the teenager cutting the cord and leaving home…. that’s for another paper, but let’s leave those newborns attached!
Ceriani Cernadas JM. Timing of umbilical cord clamping of term infants. Arch Argent Pediatr.
2017 Apr 1;115(2):188-194. English, Spanish. doi: 10.5546/aap.2017.eng.188. PMID: 28318187.
Downey CL, Bewley S. Historical perspectives on umbilical cord clamping and neonatal transition. J R Soc Med. 2012 Aug;105(8):325-9. doi: 10.1258/jrsm.2012.110316. PMID: 22907549; PMCID: PMC3423128.
Hooper SB, Binder-Heschl C, Polglase GR, Gill AW, Kluckow M, Wallace EM, Blank D, Te Pas AB. The timing of umbilical cord clamping at birth: physiological considerations. Matern Health Neonatol Perinatol. 2016 Jun 13;2:4. doi: 10.1186/s40748-016-0032-y. PMID: 27298730; PMCID: PMC4904360.
Hooper, SB, GR Polglase, and AB te Pas. 2015. “A physiological approach to the timing of umbilical cord clamping at birth.” Arch Dis Child Fetal Neonatal Ed 100(4): F355–60.
Winkler, A, Isacson, M, Gustafsson, A, Svedenkrans, J, Andersson, O. Cord clamping beyond 3 minutes: Neonatal short-term outcomes and maternal postpartum hemorrhage. Birth. 2022; 00: 1- 9. doi: 10.1111/birt.12645