[In utero measurement of the umbilical cord in full term pregnancy]
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A Durand1, P Descamps, P Vieyres
1Unité INSERM 316, Laboratoire de Biophysique Médicale, Tours.
Objective:
The length of the umbilical cord varies widely from one pregnancy to another. Although its average length is 50 cm, this measurement could vary from as little as 20 cm to more than one metre. The purpose of our study was to evaluate, in utero, the length of the umbilical cord during the third trimester of pregnancy knowing the propagation velocity of the pressure wave along the cord.
Material And Methods:
The computation of the apparent length requires two ultrasound transducers, one situated at the aortic fetal arch, the other at the placental extremity of the umbilical artery. Knowing the velocity of the pressure wave (v), as well as the time interval between the systolic peak of two waves (delta t), we can deduce the length of the umbilical cord (delta t x v).
Results:
The comparison between the calculated length and the actual length measured shows a significant correlation with a probability of 1%.
Conclusion:
The knowledge of the length of the umbilical cord is quite useful in the physio-pathological interpretation of the placental resistance index. It is also of interest, before the delivery, to know the length of the cord in order to foresee dystocy and how it relates cord which is either too short or too long.