Is medicine changing human genetics, eventually leading to a physically less-capable type of human?
Yes, is the surprising implication of research by Dr. Michael W. Varner and others at the University of Utah. Their article, "The Intergenerational Predisposition to Operative Delivery," is the lead piece in the June issue of the journal Obstetrics & Gynecology.
The research focused on the question of whether women who were born by Caesarean section were also more likely to have children by the operation once they reached adulthood themselves. Varner, chief of the material-fetal division in the University of Utah Hospital of Obstetrics and Gynecology, headed a study that compiled birth certificate statistics.
The team examined birth certificates of women who were born in Utah between 1947 and 1957, as well as of their children who were born in the period 1970-1991, checking for which ones were born by Caesarean delivery.
Until recent decades, it was considered so dangerous that it was an operation of last resort, when the mother or child's life would be jeopardized by normal birth.
"Women who were delivered by Caesarean were at increased risk of subsequently delivering their children by Caesarean," concludes the report by Varner, Alison M. Fraser, Cheri Y. Hunter, Patrice S. Corneli and Ryk H. Ward, all of the University of Utah.
"The State Health Department allowed us access to these records on a strict promise of confidentiality, so no names are available, and there's no way for us to identify any individuals, or contact people," Varner said in an in-ter-view.
"The bottom line, basically, is that if you take all women born by Caesarean section . . . they're 41 percent more likely to have to have a Caesarean section themselves."
Results are even more telling in particular categories. Women born by the use of mid- or high-forceps are 72 percent more likely to have babies by Caesarean section today. Women who were delivered by Caesarean section because they were too big for normal births, were 83 percent more likely to have babies by the procedure.
"The biggest risk of all was if the mother's labor was considered abnormal - it's called dysfunction. It's 597 percent, a six-times greater risk" that if she should have a child herself, it would be delivered by C-section.
What this may mean is that traits that in the past killed many mothers during childbirth - such as uteruses or pelvises that are poorly equipped for child-bearing - no longer take the same terrible toll. Nowadays, such traits can be passed on to children who would have died in an earlier era.
By far, most increases in Caesarean rates can be attributed to physicians changing the way they manage pregnancy. "Nevertheless, our data identify a real biologic phenomenon," the study adds. Its data jibe with the likelihood that women can inherit physical conditions that cause poor uterine contractions or soft tissue relaxation during labor.
By what percentage did Caesarean sections increase in mothers who were themselves born that way? "It turns out that the answer . . . is only 31/2 percent," he said.
That figure doesn't seem high. But it is the change in one generation, and "over a course of some number of generations, it will likely become more of a problem, just because the selective advantage of being able to have a vaginal delivery may no longer exist."
Another study Varner and his colleagues recently completed shows that if a Utah woman was born prematurely - particularly if she was born at least six weeks early - she's twice as likely to have premature children.
By saving more mothers and children through Caesarean section, better care of women with dangerous complications at childbirth and the saving of more premature babies, "we may be creating more problems in future generations," he said.
"At some point, long beyond our lifetimes, that may be associated with a profound difference in how babies are delivered."
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Additional Information
Longtime doctor detects a birth pattern
Dr. Michael Varner discovered a pattern over many years of practice as an obstetrician/gynecologist:
"You work for a very long time with somebody in labor to try to get them delivered vaginally. It just isn't going to work. You go out into the waiting room and talk to the family, say `I'm sorry, this is just going to come to a Caesarean section.' They say, `Oh, we're not surprised. She (the mother-about-to-be) was delivered by Caesarean section, and all of her brothers and sisters were too."
Could the fact that her mother had a successful C-section influence a woman to think she also should deliver that way? "We haven't really addressed anything in terms of psychology of all of this," he said.
Are more women having Caesarean section? "That's very much an issue. The historic reality of Caesarean section as a life-threatening, last-resort procedure no longer exists. In fact, it is widely perceived as being less risky, less painful, than normal delivery."
However, the facts go against that perception. Women with C-sections are about four times as likely to be at risk than if they are able to have the baby vaginally.