Uterine size, parity and umbilical cord length

It seems to be a widely held notion that the uterine cavity is larger during a woman's later pregnancies than during her first pregnancy. The direct evidence for this is, however, scarce. The umbilical cord length at term is one measure of the fetal intrauterine mobility, and therefore indirectly of the space in which the fetus moves. If the uterine cavity is larger during later pregnancies, the cord length of the babies in these pregnancies should be longer. We have compared the cord lengths of 1839 babies, divided into three groups: babies born of primiparous, secundiparous and tertiparous women. The difference in mean cord length is statistically significant between the first and the third group. This supports the theory of a larger intra-uterine space in later pregnancies. We also examined 159 mothers, measuring the umbilical cord length of their first and second babies. A significant positive correlation was found, in that the first baby tended to have the shorter cord. A control group with matching, but unrelated babies showed no such correlation. The results seem to us to support the stated theory further.