Dynamics of Umbilical Cord Circulation: During gestation, the fetus relies on the circulation of blood through the umbilical cord to exchange oxygen, carbon dioxide, nutrients, and waste products with the placenta. The fetus and the placenta develop a delicate balance in distributing blood to promote growth and development. Doppler velocimetry of the uteroplacental and fetoplacental circulations is commonly used by obstetricians to assess fetal growth restriction.

Placental Transfusion: After birth, part of the blood contained in the placenta can be transferred back to the newborn, known as placental transfusion. There are several methods to indirectly assess the size of placental transfusion. One such method is measuring the residual placental blood volume (RPBV) after cord clamping. Studies have shown that RPBV decreases from approximately 109 ml to 17 ml when cords are clamped immediately, indicating a smaller transfusion. Similarly, comparing the weight of babies after early and delayed cord clamping shows an average weight gain of 86-96 g in delayed clamping cases, corresponding to a placental transfusion of approximately 30 ml/kg.
Other methods to indirectly demonstrate placental transfusion include measuring neonatal blood volume, which has shown an increase of 14-20 ml/kg in delayed cord clamping cases. Hematocrit and hemoglobin levels in neonates have consistently been found to be higher after delayed cord clamping, with differences of approximately 1.5 g/dL and 10%, respectively. Improved iron stores have also been observed up to 8 months after birth in cases of delayed cord clamping.

Beneficial Effects and Optimal Timing: Delayed cord clamping has been associated with numerous benefits, such as improved iron stores, reduced anemia, enhanced neurodevelopment, and lower transfusion requirements in preterm infants. Studies have shown that waiting at least 2-3 minutes after birth for cord clamping is recommended to achieve optimal outcomes.

Conclusion: Understanding the dynamics of umbilical cord circulation and placental transfusion is essential for healthcare professionals and individuals interested in medicine. Through a review of extensive literature, it is clear that delayed cord clamping leads to various benefits for newborns. Recommending a minimum of 2-3 minutes for cord clamping after birth can help optimize outcomes. Further research and ongoing studies, such as the SAVE-study, contribute to our understanding of sustained cord circulation and its implications for neonatal health.

Read more: https://doi.org/10.1016/j.semperi.2023.151739