In the past, the newborns' umbilical cord was not clamped right after birth, thus allowing the blood flow to stop naturally. This practice, known as "late clamping", was replaced by "early clamping", that is, cutting the cord immediately after the infant is expelled. However, this new practice lacks studies corroborating its benefits. In fact, recent studies on the importance of when clamping should be done have shown contradictory results.
A doctoral thesis carried out at the Department of Obstetrics and Gynecology at the University of Granada (Universidad de Granada [http://www.ugr.es]) by Catalina de Paco Matallana shows that the clamping of the umbilical cord of newborns from full-term pregnancies (that is, infants born after a nine-month pregnancy) two minutes after the infant is expelled from the womb makes no difference to hematocrit or hemoglobin levels of the umbilical cord vein compared to clamping the cord within 20 seconds. Thus, the study shows that early clamping (which is widely performed) is not justified.
Analysis of 151 umbilical cords
The doctoral thesis Repercusiones clnicas y fisicoqumicas del tiempo de ligadura del cordn umbilical en recin nacidos a trmino (Clinical and Physiochemical Repercussions of Clamping Time of the Umbilical Cord of Newborns from Full-Term Pregnancies) analyzed a total of 151 umbilical cords of newborns from full-term pregnancies. In 79 cases, the umbilical cord was cut within 20 seconds, and in 72 cases it was clamped two minutes after the infant was expelled.
The study found that the partial pressure of oxygen in the umbilical artery of the newborn babies who had late clamping had risen, while there was a lesser need of oxygenotherapy after birth. There were no differences in the removal time of the placenta and the mother's bleeding after birth - one of the reasons why early clamping of the umbilical cord started to be practiced.