Wider pelvis is said to facilitate childbirth
Women naturally have a slightly wider pelvis than men so that there is enough space for the baby's head at birth. As a Swiss study has now shown, the pelvis obviously becomes particularly wide when the woman reaches her most fertile age. As the scientists at the University of Zurich currently report in the journal "Proceedings of the National Academy of Sciences", the width of the female pelvic girdle increases significantly from the beginning of puberty, but then becomes narrower again from around 40 years of age. This “reprogramming” is therefore probably directly related to the changes in the female hormone balance.
Widening begins with the onset of puberty
If a woman is relatively broad in the middle of the body, this is often colloquially referred to as a “childbearing pool”. Not without reason, because the female pelvis expands in the course of childbearing time to prepare the body for an upcoming birth. A wide pelvis makes it easier for the child to exit, while a very narrow pelvis exit can cause complications during birth. Now researchers led by Marcia Ponce de León from the University of Zurich report in the "Proceedings" how exactly these changes in the female anatomy take place. Accordingly, the widening begins from the beginning of puberty until the female pelvic girdle reaches its maximum width at the most fertile time. In the further course of life the pelvis would narrow again.
"From the age of about ten, the development in women changes substantially, while the male development continues its earlier course," the experts write in their article. "Around the age of 40 to 45 years, female development changes again, in a direction that largely corresponds to male development," the scientists continued.
Only minor differences between the sexes in childhood
For their project, the scientists had examined a total of 275 healthy people using computer tomography (CT) in order to be able to understand the development of the pelvis over time. It was shown that there are slight differences in this area between the sexes from the outset - but these only really became clear at the beginning of puberty. Because between the ages of 15 to 25 years, women would e.g. change the location of the ischium-pubic region, which widens the pelvic exit and the distances between the acetabular cups. "All in all, these changes in development lead to a broad birth channel that is favorable for birth," the team continued. These changes would culminate between the ages of 25 and 30, and it was irrelevant to the researchers whether the woman had a child or not.
Interplay of genes and hormones
This special structure of the female pelvis is probably due to a complex interplay of hormones such as Attributed to estrogen and certain genes and would be preserved until menopause. "The female organism can obviously broaden the pelvis on demand" and is not simply at the mercy of a genetically determined development program, "Ponce de León is quoted in a statement from the University of Zurich. At the same time, the hormones are also heavily influenced by nutrition and environmental factors. “Accordingly, birth difficulties are less of an evolutionary problem. Rather, it seems to be a question of the balance between the hormones and external factors that influence the size of the birth canal and the prenatal development of the child. "
But why does the width of the pelvis decrease again after the woman of childbearing age? According to the researchers, this is probably related to the upright walk. Because a narrower pelvis has a stabilizing effect on the pelvic floor and thereby helps to absorb the high pressure that arises from walking in the lower abdomen. “During a woman's life, the dilemma is first alleviated in one direction by widening the birth canal during the most fertile phase, and then in the other by narrowing the dimensions after menopause,” the scientists conclude in their article. (No)