Development of valves in the small saphenous vein in human fetuses.

The study was performed on 82 small saphenous veins in human fetuses of both sexes aged 9 to 37 weeks. The earliest valves were observed in 13 week-old fetuses. In fetuses between 13 and 18 weeks old the number of valves increased from 1 to 8. In the older fetuses between 19 and 37 weeks the number of valves varied from 5 to 9 and does not seem to be related to age. During development more valves were found in the upper part of the small saphenous vein. The height of valves increases with age and differs between particular valves of the same vein.