Born Female: The Relationship Between Stress, Miscarriage, and Girl Power

Wednesday, November 01, 2017 by Meg   •   Filed under Psychology of Motherhood

Do we prefer baby boys over baby girls?

We have certainly heard about these preferences in other countries. Some places have seen parents murdering infant girls so they can try for a boy, particularly where population restraints made more children illegal. In these cultures, there was a time when not bearing a son was grounds for divorce. Obviously some cultures have a strong male preference. 

But this isn’t just an issue overseas. The preference for boys over girls is rampant here in the US of A.

Isn’t it? 

Research has shown that women who have first-born girls are less likely to marry1. Even in utero, an ultrasound tech’s exclamation of, “Daughter!” reduced the chance of nuptials. Women with first-born daughters were also more likely to end up divorced and fathers were more likely to seek custody of sons following divorces1. Researchers believed that this was due to either an overt or subconscious preference for boys over girls1

Of course such assertions make sense in a patriarchal society. After all, girls are weaker. We’re more emotional. We need too much. We are less likely to succeed. The odds are stacked against us. Why wouldn’t we want boys, even if only on a subconscious level? 

Why not desire boys? Because the conclusions of theses earlier researchers might be fucking baloney. Things are not always what they seem.

Why Women With Girls Are Statistically Less Likely To Marry (SPOILER ALERT: It’s Not the Girls)

While pregnant women who end up having daughters do indeed get dealt a shittier hand in terms of marriage prospects and divorce rates, it might have less to do with the child and more to do with the fact that females, even in embryonic states, tend to fare better in harsher uterine environments than male embryos2. So, when the stress hormones are too high during pregnancy, a woman who happens to be carrying a boy may experience miscarriage, often even before she knows she’s pregnant. Girls are heartier. We can withstand more, even in the womb.

This female survival advantage is not new; evolutionary psychologists, anthropologists and contemporary research psychologists and sociologists can all show evidence that women of all ages tend to be statistically more likely to survive until their next birthday. This may have to do with reproduction and the survival of the species overall, as mothers and other close females were more instrumental in offspring survival, therefore more vital to the survival of the species as a whole. From this standpoint, females are just stronger in terms of longevity and can withstand more before breaking (or dying). Just as sperm carrying females tend to be slower but heartier than the fast but more easily killed male sperm, baby girls are less likely to end up miscarried. 

Girl power, and all that shit. But how would this come about? 

Stress and The Evolutionary Advantage of Miscarriage

Stressful environments have historically been ones to lead to infant demise. And the sheer use of resources needed to actually complete a pregnancy make costs extremely high for mothers. In other words, no use wasting resources carrying a pregnancy to term if the environment is stressful enough to make survival of the child unlikely.

Mechanisms for miscarriage (also known as “spontaneous abortion” in the literature) is present in other primates. In The Woman That Never Evolved, Sarah Blaffer Hrdy notes that in primate populations, dominant primates can trigger spontaneous abortion in subordinate members of the group, females that tend to be generally more stressed than their more dominant counterparts3

Why would slightly more evolved women not come equipped with such a default mechanism? That’s just poor evolutionary planning. 

And Mother Nature ain’t no sucker. 

In humans, this mechanism has been difficult to research because spontaneous abortion tends to occur VERY early, often before most women even know they are pregnant. This is part of the reason for the lack of research in this area; because women who don’t know they are pregnant can’t very well join a study about it.  

What meager research there is indicates that high cortisol—a chemical actively involved in the stress response—is associated with higher rates of spontaneous abortion4. It also indicates that higher stress may be a factor in recurrent miscarriage5 and that severe stress—such as exposure to rocket attacks both before conception and in early pregnancy— is associated with spontaneous abortion in the absence of any physical harm6.

It’s only recently that researchers have started trying to crack the code about what mechanism might actually be in play here. 

Some recent studies note that stress triggers the release of corticotropin-releasing hormone (CRH) which causes the hypothalamic-pituitary-adrenal (HPA) axis to kick into gear7

Okay, that was a hell of a lot of big words. Let's stick with the acronyms, shall we? 

CRH is released in response to stress and is also produced by the placenta to trigger contractions for delivery. But CRH and it’s analog urocortin (Ucn) are also released in other areas outside the brain where they target mast cells. 

Mast cells are most often associated with allergic reactions and are abundant in the uterus. This is one reason that occasional   researchers hypothesize that overreaction of these cells might trigger morning sickness in some women if responses are misinterpreted as an allergy to the foreign fetal DNA. However this is another area that needs more study.

But back to the CRH released in response to stress. Aside from theoretically making some of us puke our guts out, research indicates those mast cells may respond to the extra CRH by secreting trypase and interleukin-8 that in turn leads to miscarriage7. And as noted earlier, girls may be able to survive these stresses at higher rates. 

In these early phases of pregnancy, boys may simply be lost more, often without women realizing it. This might explain the fact that highly stressed women have more girls: they may be more likely to be under pressure due to a stressful home environment already. The divorce or lack of relationship stability may be a contributor to miscarrying boys as opposed to girls being a trigger for relationship strain. 

Some of us were born only because we happened to be girls. And girls rule.

Now, some of this might have people a little up in arms. After all, if increased stress has the potential to cause miscarriage, doesn’t that mean that it’s our fault?

“What the hell, Meg! I thought you always said don’t be a dick! Now you’re going to try to blame bereaved mothers for losing a pregnancy?”

No. No, no and good, god no. Because again, the vast majority of miscarriages that occur later in pregnancies are the result of genetic abnormalities, not stress. The majority of these spontaneous abortions occur before a woman even knows she is pregnant at all, usually within the first three weeks of pregnancy, or five weeks from the date of the last period4. If you are grieving the loss of a pregnancy you were well aware of, rest assured that in all likelihood, the statistics favor other factors besides stress-related miscarriage. 

Plus, let’s be honest, we all try to be mellow. No one chooses being stressed on purpose. Unless you happen to be the woman married to Ronald Sterling. Or maybe you’re dating Donald Trump, or for-fuck’s-sake-why Rush Limbaugh. GET OUT NOW, GIRL! 

But I digress. What does all this mean for us now that we’re here? Might these issues be the reason women are statistically more likely to suffer from certain mental illnesses and issues with anxiety in particular?

Stress in Utero and Future Mental Illness 

Women are more likely than men to have generalized anxiety disorder, twice as likely to suffer from panic disorder or social phobia and three times more likely to have agoraphobia (fear of being in public places or leaving the house). Is it possible that because we are more likely to be the ones born into stressful environments, we might also have more anxiety later? 

While there are clearly other factors at play, such as hormonal shifts and our overall societal treatment of women including actual power differences, there might be some science to back the claim that early stress may be contributing to our later anxiety. Dr. Robert Sapolsky, author of Why Zebras Don’t Get Ulcers, believes that stress in utero can alter stress levels in infants. His primate research has verified such links, noting that stressed mothers have infants who secrete higher levels of stress hormones and that these higher levels of stress hormones tend to persist over time8. The reason for this is simple: baby animals need to know how stressful the environment is before they are born and retain whatever stress response is needed to survive. 

Say I’m a fetus who will one day be coming into a mellow environment. Great! I don’t need quite so much stress responsiveness. I can be born chill like The Big Lebowski with low cortisol, lower sensitivity to amygdala response and still survive to procreate, the main measure of species success. 

But what if my momma is stressed during pregnancy? Uhoh. I better come out with a super active stress response if I expect to survive. I need high cortisol and must be ready to run at a moment’s notice. If the environment mellows out later, whatever. I’ll just feel anxious. But it’s better than risking not being fast enough when whatever is stressing mom comes after me.

Sapolsky isn’t the only one to recognize the influence of maternal stress on infant anxiety. Other researchers note that all this early exposure to stress can alter the HPA axis in unborn children9, a system involved in anxiety responses and depression.This makes sense as the hormones released (including CRH) trigger the HPA in mom, and those chemicals work in babies also. 

If the in-utero environment breeds more stressed babies, and those babies are inherently more likely to be girls due to early male miscarriages, it makes sense for our anxiety rates to be higher. And those same early environments that made mom stressed when she was pregnant may add more strain during childhood through poverty, parental separation and loss, or even abuse, all of which up the odds for later mental health issues.

Now this leads to an interesting ethical question that you may be able to assist me with. While I am not one to poke too much into the political arena, there seems to be a strange dichotomy inherent in this particular issue of stress and fetal loss. If stressing pregnant women has the potential to trigger spontaneous abortion it seems that we as a nation, particularly our more right-winged brethren, might be inclined to see if there are ways to reduce such strain, particularly because excessive strain is also more likely to lead some women to seek actual abortion. Might there be a political or ideological argument here for more mental health treatment availability across the board? Can we make a pro-life argument for mental health services in every population? This is obviously tricky when those same individuals who push for the sanctity of the fetus are often (though not always) those who would refuse bills that would assist with getting this mental health care to those in need. 

How to handle such a thing when it is at odds with other ideologies within the same party is obviously a tricky question to answer and one that cannot be done justice here. However, it might be the beginning of an interesting discussion.

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Topic-Relevant Resources

Conviction: An Ash Park Novel (#2)
Conviction runs deep. Courage runs deeper.

We've Got Issues: Children and Parents in the Age of Medication
Judith Warner explores the misunderstood issue of overmedication in relation to children's mental health.

The Woman That Never Evolved
Monkeys, anthropology, girl power and evolution.