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Why Pregnant Women Don't Tip Over

About a year ago, Discover Magazine assigned me to write a story covering a Harvard study about intriguing evolutionary adaptations in the female spine. A look into “why pregnant women don’t tip over,” as Nature, the journal that published the research, cleverly called it, the study found evidence that the female spine evolved differently from the male’s, and that these changes apparently help lessen the biomechanical strains of pregnancy.

Publication of the story kept getting delayed for various reasons out of my control—this is a common (and fun!) aspect of being a freelance journalist—and eventually was killed. It made me sad. It was such a great little story.

Insh’allah, my back won’t start to hurt for a while. Still, the piece has been on my mind. I’ve been meaning to follow up with the researchers to see if they’ve since investigated further.

The research was pretty widely covered, but in case you haven’t heard about it, here was my take.

Women’s lower spines may have developed extra strength and flexibility to keep them upright and reduce back pain while pregnant. By tracking 19 women over the course of their pregnancy, researchers at Harvard University and the University of Texas at Austin explored the biomechanics of human pregnancy to tease of the female spine’s evoluationary adaptations. It turns out a curvy spine helps mothers-to-be maintain balance, reduce muscle fatigue, and prevent vertebrae from shifting or breaking during pregnancy.

Hominins developed the lower back curve, or lumbar lordosis, around the time they began to walk upright. To investigate the biomechanical challenges to bipedal stability posed by pregnancy, Katherine Whitcome, then a graduate student, and UT anthropologist Liza Shapiro tracked 19 women over the course of their pregnancy. On average, the women’s center of mass shifted 3.2 centimeters in front of their hips, and out of alignment with the lower body’s supporting joints. To compensate, the women naturally leaned back, increasing the lordosis by as much as 60 percent. The research showed that this stress is partly alleviated because the lordorsis in women extends across three vertebrae. It spans only two in men. Plus, women have larger spinal joints, called zygapophyses, than men do. Chimpanzees lack the lordosis entirely. “The zygapophyses are better able to resist the spinal loading environment of pregnancy,” says Whitcome. “They are less likely to fail or fracture under constant and long duration of back extension.”

After moving to Harvard, Whitcome and primate fossil specialist Daniel Lieberman then looked to the hominid fossil record to see when the adaptation may have arisen. Two specimens from the firmly bipedal Australopithecus africanus, presumably one female and one male, showed the same dimorphic lumbar traits. How far back in hominid history the adaptation goes, or how common it is across bipedal hominid species, is unknown, because the fossilization of vertebrae is extremely rare.

Lieberman wonders whether women have given up anything up by being able to better able to stabilize their spine. “We don’t know what—if any—disadvantages there are,” he says. “This is an interesting problem, actually. One assumes there must be a trade-off or one would expect to see the pattern in men. My guess is that this configuration limits mobility a little.”

The research has inspired new areas of inquiry for the team. One is the biomechanical challenge of carrying a baby around, which doesn’t end after a woman gives birth, Whitcome notes. But while a mother carries a fetus in one place—the womb—after birth she may carry a child in any number of ways—on her hip, on the front of her body, or on her back. “We’re designing some studies to look into the biomechanics of carrying an infant. What does it mean for upper-body loading?”

Another is the fetal cranium. It’s well known that the female pelvis was under strong selective pressure to accommodate rapidly enlarging fetal skulls. Did fetal skulls in turn adapt to travel through the birth canal of an upright mother? Human faces lack a “snoutiness” common to other primates. Some hypotheses attribute the development of our flat faces to changes in diet, or a need to balance the head. But Whitcome wonders whether reproductive pressures had a hand in this change, too, as part of the whole “suite” of skeletal adaptations that accompanied bipedalism.

She suggests the spine may once again be the key to finding out. During primate labor, the infant’s snout leads the way through the birth canal. But a human baby tucks its chin and goes crown first. It can move this way because of the foramen magnum, a hole at the base of the skull through which the lower brain and spinal cord are connected. In nonhuman primates and other quadrupeds, that hole is in the back of the skull. In humans, it is found underneath the skull, which “helps us to balance our heads very nicely,” says Whitcome. “But it also limits how much we can roll our heads forward and back. It may preclude the human fetus from extending its head as it moves through the birth canal. How much would a very snouty face, as chimps have and our early ancestors had, interfere when the foramen magnum moved?”

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Want a Scary Pamphlet?

Around week 13 of the pregnancy, HusbandMan and I had a genetics counseling session. This was both more and less high-tech than it sounds. The counselor, a cheery, pretty woman named Anya, ran through our family histories to determine which genetic disorders The Kid might have a chance of inheriting.

From what she learned, she would suggest a battery of tests that were technologically impossible when HusbandMan and I were ourselves in utero, among them a triple screening, which checks for two types of Down’s Syndrome (extra chromosomes on the 18th and 21st pairs) through blood tests and also uses a diagnostic ultrasound to measure nuchal translucency (the fluid beneath the skin behind baby’s neck); as well as tests for spina bifida, spinal muscular atrophy, and the moodily sci-fi-sounding Fragile X, which, as you knew quite well in middle school, afflicts “retards.”

Anya went about the assessment by flipping over the 8 1/2″ x 11″ sheet of paper on which I had filled in our basic stats and, in ball-point pen, sketching a rough dual family tree. It looked like something your drunk uncle might lay out at the kitchen table one night to convince you the family is, indeed, related to Charlemagne.

On this family tree went the grandparents with Alzheimers and diabetes and emphysema; the aunts and uncles with strokes and heart disease; the parents with cancer; the second cousin born with a missing finger and a half, which is probably a bit inconvenient but is also kind of cute; and the most common ailment—the impressively multigenerational, cross-family prominence of alcoholism.

The easiest question was also the broadest: “Is there any chance you two are related?”

I burst out laughing. “That would be funny! Can you imagine? Dear lord. The poor kid.”

Anya looked startled. HusbandMan cleared his throat and said, “No, not a chance.”

Based on our family histories, she gave us her suggestion (the triple screen; weeks later we would also test for SMA and Fragile X) and a handful of pamphlets. We went back to the waiting room; soon I’d get needled and drained by the phlebotomist.

The room was full of pairs, women and men and sometimes women and older women, presumably the grandmothers of the tots-to-be. The more pregnant a woman appeared, the grumpier her countenance. I wondered what new and exciting ways of expressing Don’t fuck with me or I will KILL you I was going to learn in the last months of pregnancy. I liked the idea. I’m always seeking clear ways to communicate.

As HusbandMan checked his phone for messages from work, I read through the information Anya had given us. Each pamphlet was a trifold of horror delineating the complications and pains of genetic disorders. Feeling resentfully well informed, I decided to share the misery. I fanned out the pamphlets like a poker hand and offered them to HusbandMan.

“Want a scary pamphlet?” I said, too loudly. Several people stared.

HusbandMan raised his eyebrows. “Uh, yeah. No. But thanks.”

Anya’s question about the possibility of our being related struck me as funny, but of course there are lots of people who are related who do have children. There are many genetic disorders among these populations, which are relatively “closed”—by religion, culture, geography or a combination of all three; among them are the Amish and certain sects of Ashkenazi Jews.

HusbandMan and I had, actually, done genetic testing before. Along with a bottle of really nice wine and a long weekend in Maine, for our 10th anniversary we got ourselves genetic testing kits through the Genographic Project. By tracing our mitochondrial DNA, which is passed from mother to child, we would find out something about our deep ancestry: where our genes, and more specifically the women who walked around with them, were 30,000 years ago. Our genetic information would also be stored (anonymously) in a global database. Who knows what we’ll learn about our common ancestral past—and its potential for the genetics of the future—from this database. So we swabbed the insides of our cheeks and mailed off the samples.

You know what we found out? We’re white people. I know—we were shocked too.

But no genetic test yet available can answer the question Anya didn’t ask us: What do you fear The Kid might inherit that won’t show up on these tests? Because some of these things are nature, and some are nurture, but most are probably some melding of the two and impossible to tease out, at least at this stage of our knowledge (and perhaps never).

We’ve talked about how with The Kid I’m going to restore height to the Bartoo line, and he’s going provide the Pinkowskis with lips for the first time in history. The Kid is sure to be smart, and he’ll probably artistically minded and pretty athletic. We hope he’ll be curious, compassionate, and good with his hands. We hope he’ll make things and grow things.

Like all expectant parents, we can imagine the best of ourselves distilled into him. We fantasize about raising a person who embodies all that we love in each other and have made peace with in ourselves.

But what if the opposite were to happen? What if instead all our worst qualities were to combine and duplicate? In short, what if we were to make a jerk? A genetically determined jerk? A mean little troll of a guy, with a quick temper and long periods of depression, who is flighty and scared, self-righteous and indecisive, self-pitying and bossy? Who is hypoglycemic and has bum knees? Who is a drunk? And not a fun drunk—the kind you have a blast with but worry about the next day—but a real dickhead of a boozer—the kind who picks fights and throws stuff and gets racist?

There’s a universe of The Kid’s development we have no say in, despite his being half me and half HusbandMan. And the independent entity he’s going to be several months? That’s when the nature/nuture issue will really start to play out.

In the end, all the genetic tests came out fine. Now we only have to spend the next 18 years doing everything we can to foster the development of a decent human being.

I wish there were a test to determine whether we have what it takes to do it.

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Drinkin' for Two

It’s New Year’s Eve 2008. I’m 10 minutes late, as always, to join HusbandMan and friends for dinner at a French restaurant where we’ve spent the last two NYEs. Layer after layer comes off, and finally I am in my seat. HusbandMan immediately begins rubbing my belly like a genie lamp.

“It’s like a kitten!” he exclaims.

I hit the bread and butter, and then more bread and butter, and eventually I feel like I have enough food in my stomach. It’s time. I pick up the bottle, I pick up a glass, and I pour. The wine glitters burgundy. My hands cup around its warmth. I lean over the rim and inhale. Oh yes. This is the upside of superpowered Knocked-Up Nose: while many aromas turn bad and bad ones are devastating, good aromas are utterly sublime. Like this wine’s: red and smooth, velvet without weight, wood and water and forest. I want to wrap it around me like a fleece blanket. I do the next best thing: take a sip.

“Oh god!” I cry out.

My friends look startled. Suzy demands, “What?!”

“It’s so good! It’s not fair! Why can’t I drink? So what if The Kid’s a little slow? We’ll love him anyway, right?”

Step out of your glass houses and get ready to cast your stones, because here it is: that wasn’t the first glass of wine I’ve had during my pregnancy, and it isn’t going to be my last. After the first trimester was over, I decided to allot myself one glass of wine a week, with a meal.

Call Child Protective Services! Abusive mother-to-be on the loose!

If you thought the world was fraught with peril—disease, violence, stupidity, Dick Cheney—try going through it knocked up. Danger lurks everywhere. The world itself is an evildoer manically twirling its mustache and tying fragile Vessels of Motherhood to railroad tracks.

There’s a kind of puritanical hysteria around pregnant women in the U.S. that really rubs me the wrong way for two reasons: puritanism, and hysteria. When HusbandMan and I decided we weren’t exactly trying to conceive a child—instead we were, as HusbandMan put it, “not not trying”—neither one of us thought that upon success I would be required to relinquish all ingestible pleasures and all rational thought. (Hormones would do a bang-up job on that last part anyway.)

But to read virtually all the guidelines on pregnancy behavior, you’d think I was supposed to be hermetically sealed in germ-free floating bubble for 10 months, my only joy the contemplation of motherhood, my only thought the contemplation of motherhood. Certainly I would never drink a glass of wine, an act akin to ingesting bleach, having an insecticide cocktail, imbibing a pure poison potable. Surely I’m not the most evil, selfish woman on the planet—perhaps only the 27th or 28th.

Bah. Bah! My mother drank. Your mother drank. Their mothers drank. Generations upon generations of women drank—and some still are. We have millennia of empirical evidence that alcohol in moderation is not harmful.

Yet this is what we’re told by the National Institutes of Health: “It is not known if there is any safe drinking level during pregnancy; nor is there any stage of pregnancy in which drinking—at any level—is known to be safe.”

The fact is, there is little evidence that drinking light to moderate amounts of alcohol during pregnancy has a negative effect. The truly frightening evidence for fetal alcohol syndrome is related to heavy drinking.

In a 2006 article in the NYT called “The Weighty Responsibility of Drinking for Two,” food writer Julia Moskin, at the time pregnant with her second child, writes that a pregnant woman’s “responsibility for minimizing risk through perfect behavior is vast.”

And it’s not just alcohol—Ye Shall Fear fear canned tuna, sushi, soft cheese, deli meats, caffeine, jumping, sleeping on your stomach, sleeping on your back, too much weight gain, not enough weight gain, peanut butter, honey, stress, hair dye, cat poop, bending…the list is endless. Yet, as Moskin writes:

Proof, it turns out, is hard to come by when it comes to “moderate” or “occasional” drinking during pregnancy. Standard definitions, clinical trials and long-range studies simply do not exist.

“Clinically speaking, there is no such thing as moderate drinking in pregnancy,” said Dr. Ernest L. Abel, a professor at Wayne State University Medical School in Detroit, who has led many studies on pregnancy and alcohol. “The studies address only heavy drinking” — defined by the National Institutes of Health as five drinks or more per day — “or no drinking.”

You know who drinks five drinks a day? An alcoholic, or an idiot, or a combination thereof. You know what most of us who drink aren’t? Alcoholics. (Many of us are indeed idiots.)

Look, I know I sound cavalier. And of course I don’t want to do anything that would harm our child. But I don’t believe I am. Of course, this isn’t an issue of faith; it doesn’t matter what I “believe.” It’s about proof. Like Moskin, I’ve looked for it.

New research that specifically fills in the clinical gap between heavy drinking or no drinking mentioned in the NYT article came out last fall, in an article published in the International Journal of Epidemiology, a peer-reviewed scientific journal published by Oxford University Press. It was a very large study: nearly 12,500 women in the U.K. were studied for the effects of drinking during pregnancy. Specifically, their 3-year-old children were tested on a range of cognitive and behavioral metrics. For this study, women who had one drink a day were considered heavy drinkers (a far more conservative estimate than the five a day estimate by the NIH—and far more than I’d be comfortable drinking, personally). Light to moderate drinkers had one or two drinks a week or per occasion.

As lead author Dr. Yvonne Kelly says in the UCL press release:

[V]ery few studies have considered whether light drinking in pregnancy is a risk for behavioural and cognitive problems in children.

Our research has found that light drinking by pregnant mothers does not increase the risk of behavioural difficulties or cognitive deficits. Indeed, for some behavioural and cognitive outcomes, children born to light drinkers were less likely to have problems compared to children of abstinent mothers…

The study data shows that boys born to mothers who drank lightly were 40 per cent less likely to have ‘conduct’ problems and 30 per cent less likely to have hyperactivity, even when a range of family and socioeconomic factors were taken into account. Boys born to light drinkers also had higher scores on tests of vocabulary and whether they could identify colours, shapes, letters and numbers compared to those born to abstainers.

Girls born to light drinkers were 30 per cent less likely to have emotional symptoms and peer problems compared with those born to abstainers, although this appeared partially explained by family and social backgrounds.

Ha! Take that, abstainers! If I had a car I’d get a bumper sticker that says, “My drunk fetus outperformed your sober one.”

Kidding! Though somebody should start a really lousy punk band (is there any other kind?) called Drunken Fetus.

Anyway—the point is that our absolutism over alcohol during pregnancy passes neither the smell test nor the lab test. Maybe it would be more convincing if the U.S. were the only place on earth where women give birth, and if we did it really well. But neither is true. Instead, according to the CIA World Factbook (cue jokes about faulty intelligence here), when it comes to infant mortality rates, the U.S. ranks a lousy 41st in the world, behind virtually all of Europe, South Korea, Singapore, even Cuba. Cuba, for Chrissakes.

Though I’m comfortable with my decision, that doesn’t mean I haven’t been afraid I would be condemned for it.

During my last obstetric visit, I brought the topic up with the midwife. A 10-minute Keystone Kops-like chase of The Kid with the Doppler radar—every time the midwife got close, The Kid would squirm away, perhaps because of the transducer’s pressure—showed The Kid had a strong heartbeat. However frustrating for the midwife, all that movement was a good sign of health. My blood pressure and weight were all on target. I felt good. Hell, I was (and am) still pretzeling myself in safe but relatively advanced yogi ways.

It took me 20 minutes of other questions to get up the nerve to ask. “So, do you think drinking a glass of wine a week is a problem?”

I was particularly nervous to ask the midwife rather than the obstetrician; though I had specifically chosen a practice that had both (more on that in a later post), I was a little afraid a midwife might suggest that instead of wine I drink rose hip tea and, I don’t know, get in touch with the Cosmic Feminine or something. I was afraid that in this medical venue devoted to maternal and fetal health, alarms would go off, armed guards would come in and I would be whisked away to the Guantanamo for Bad Mothers.

Instead, the midwife rolled her eyes and sighed. “Okay, I have to give you the official answer first,” she said. “There’s no known safe amount of alcohol to drink in pregnancy.”

“But?”

“But there’s really almost no chance that having a glass of wine a week is going to do any harm at all. It’s fine. Look, you’re an adult. You can make decisions about what’s safe and appropriate.”

Wait, was I was being advised to think for myself? To untie myself from the railroad tracks?

“Some women decide they can’t live without sushi,” she continued. “Some can’t live without soft cheese—”

“I’ve been eating soft cheese if it’s made from pasteurized milk,” I interrupted. “And at least that one I can understand. At least that’s about bacteria—”

She rolled her eyes again. “Yeah, but when was the last time you heard about anyone getting Listeria?”

I was starting to really dig this midwife.

In the end, childbirth is a risky proposition for many women and children around the world. Most of the time, that’s not because of liquor. Lack of sanitation, disease, malnutrition—these are the things that kill so many. I am blissfully lucky to not have to worry about virtually any of that.

So if you see me with a big belly getting The Kid drunk, please know there’s no harm and no foul. And that I have a whole purseful of nasty bumper stickers.