Sex Can Prevent Pregnancy Complications
Could lots of unprotected and oral sex help ward of pre-eclampsia and other complications?
The question that animates much of my scientific research and a great deal of my writing is the same question that troubles so many people from adolescence onward:
Why is sex so complicated?
To reproduce sexually is to combine half of one’s DNA with half the DNA from another individual to make a new individual. The complications arise because sex involves a deal. Each offspring only gets half of your genes, so the other parent needs to bring something worthwhile to the deal. That cold biological reality applies to every fungus, plant, or animal that reproduces sexually.
Humans provide no exception. We lavish care on our children for decades, a wonderful and rewarding synergy, but one that makes each parent vulnerable to being manipulated, exploited, or harmed. And that vulnerability begins in the womb.
I was delighted that so many people read my recent story about pre-eclampsia. It highlighted a counterintuitive theory that this dangerous complication of late pregnancy occurs because, in the very early days of the pregnancy, the placenta doesn’t invade the lining of the mother’s uterus sufficiently.
To understand why, you need to realize that from the mother’s point of view, the embryo seems much like a disease or tumor. When the fetus and placenta grow larger, they come to resemble a relentless parasite, draining the mother of more resources than her body would prefer to give.
I know this view is pretty bleak, but it makes sense. If you want to understand the conflict that pits the mother against the fetus, then I recommend you read my “War in the Womb” article. Suffice to say, anything that lets the embryo ingratiate itself more intimately with the uterus could help both mother and fetus avoid the life-threatening panic of pre-eclampsia.
Dangerous dads
Even though scientists have long found themselves stumped over why three to ten percent of pregnancies result in pre-eclampsia, they have documented some reliable patterns. For one thing, women carrying their first child suffer higher rates of pre-eclampsia than those having a second or subsequent child. At first, doctors reasoned that first-time mother’s bodies might somehow not have been accustomed to the demands of gestation. After surviving their first pregnancy, these women acquire the ability to carry their next baby to term without developing pre-eclampsia.
But every woman having her first child is also having her first child with that father. When researchers looked more closely at pre-eclampsia rates of women who had already had children by one father and were pregnant for the first time to a second father, they noticed that pre-eclampsia risk was higher than for women who had both children by the same father. So far, the risk seems to arise from first pregnancies with a particular father.
Some mothers, too, seem to be at high risk for pre-eclampsia. Instead of women’s bodies being unaccustomed to pregnancy, it appears that pre-eclampsia may arise from a complex interaction between mother and father.
A reason to have more sex?
The picture grows more interesting when research accounts for how long a couple has been having sex with each other. Couples who have a lot of sex with each other — by being together a long time or being very busy in the bedroom — conceive pregnancies that are less likely to result in pre-eclampsia or the birth of a chronically small baby — a related risk. It is possible that women’s immune systems ‘learn’ to recognize molecules called HLA antigens in the man’s semen, and that this recognition extends to embryos fathered by that man.
Immune cells in the woman’s uterus often attack and eliminate sperm as though it were an invading germ (which it is). These findings constitute circumstantial evidence that immune recognition of sperm from a long-term mate, and of embryos conceived by that mate, might be the keys to the palace of full placental invasion.
Two further intriguing possibilities present themselves. First, perhaps women are physiologically more prepared to invest in the offspring of long-term partners, so their immune systems allow the placentas bearing these men’s genes to implant more deeply? These men have, by sticking around and having plenty of sex with her, demonstrated some depth of commitment. Compare this with a man who gets her pregnant on their first sexual encounter. He may embody loyalty and kindness, always acting with her interests at heart. Or he could be a flight risk, likely to disappear and leave her holding the baby.
How long a couple has had sex may be the best predictor a women’s body has of just how closely their long-term evolutionary interests align. I predict that women whose bodies are — subconsciously — confident of their partner’s commitment might somehow ‘allow’ deep implantation and cede some ground to the fetus and placenta. It is a left-field prediction, one I have thus far been unsuccessful in persuading my medical colleagues to test.
The second possibility, supported by some evidence but by no means unequivocally, is that women’s immune systems might recognize a male’s HLA antigens due to activities other than vaginal intercourse. A woman who has had a blood transfusion from her partner is much less likely to suffer subsequent pre-eclampsia. Also, couples who participate in frequent oral sex of the type that involves the ingestion of sperm by the woman may experience a lower risk of pre-eclampsia.
I was fortunate enough to correspond with Texas-based ObGyn and Medium Author Dr. Jeff Livingston about this article. He told me that the fellatio article is famous in Obgyn training programs, but that no one quite knows what to do with the information.
One can understand why.
To say that men and women have conflicting interests over fellatio and what happens to the semen after that seems a titillating truism. But perhaps fellatio has a real evolutionary function rather than being a convenient discovery for generation after generation of frustrated teenagers. In a long evolutionary history before effective contraception, some authors have suggested that perhaps fellatio served not only to alleviate that frustration but also served as an immunological primer, warding off pre-eclampsia later on.
The underlying hypotheses may well turn out to be true. More unprotected sex and more fellatio might well protect against pre-eclampsia. We need much more high-quality evidence before we can be sure. But even if such evidence eventuates, it is easier to foresee the information being the subject of listicles and tittering gossip pieces than any professional prescription.
Few, if any, couples agree perfectly on when to start having sex, how to go about it, and how often they want to do it. And the choice of sex acts they are willing to engage in can provoke further differences of opinion. But despite all the conflict, sex remains an intensely cooperative act, and the subject remains so exquisitely complex because of the ever-present tension between cooperation and conflict. A woman and her mate might have different opinions about how much sex to have or what happens to the semen, but they both would share the benefit if, by participating, they lowered the risks of pre-eclampsia.