Has improved nutrition made childbirth more dangerous?

Iceberg Floating In Arctic Sea

There’s one pregnancy intervention that everyone — midwives, doulas, childbirth educators, obstetricians — can agree on: promoting optimal nutrition.

We encourage women to get all the calories necessary to grow a baby as well as the full daily requirement of vitamins and minerals. We assume that will improve pregnancy outcomes by improving the health of mothers and babies. We haven’t stopped to consider that there’s more to improved nutrition than what is obvious on the surface. What if nutrition it is making childbirth more dangerous because babies are bigger?

[pullquote align=”right” cite=”” link=”” color=”” class=”” size=””]For most of human existence, babies were probably much smaller than they are today.[/pullquote]

Midwives and natural childbirth advocates are known to bewail the high modern C-section rate by pointing out that childbirth can’t possibly required a 32% surgical delivery rate or our species could not have survived. Leaving aside for the moment their faulty understanding of evolution, they have failed to consider a more basic reality. Childbirth today is very different from childbirth in nature because the human diet is very different from our diet in nature. For most of human existence, babies were probably much smaller than they are today.

That has important implications for both mothers and babies. On the plus side, mothers are healthier with higher blood counts and therefore better able to withstand the rigors of labor and subsequent blood loss. Furthermore, nutritional rickets, which often led to contracted maternal pelvis making it impossible to deliver a term baby, is almost non-existent in industrialized countries.

On the minus side, the risk that a baby will grow too large to fit through the maternal pelvis leading to obstructed labor and the death of mother and baby has almost certainly increased. In modern societies we bypass that deadly result with C-sections.

A 2012 study in the Journal of Pediatrics shows that newborn size has been increasing.* Eighty year trends in infant weight and length growth: the Fels Longitudinal Study found:

Infants born after 1970 were ~450g heavier and ~1.4cm longer at birth, but demonstrated slower growth to one year, than infants born before 1970. Growth trajectories converged after one year of age.

Recent birth cohorts may be characterized not only by greater birth size, but also by subsequent catch-down growth. Trends over time in human growth do not increase monotonically, and growth velocity in the first year may have declined compared with preceding generations.

Newborn infants born in the years after 1970 are an average of 1 pound heavier than those born in the 40 years prior to 1970. Why?

[F]actors that have been responsible include changes in maternal biology and health (including a reduction in smoking prevalence and improved nutrition unrelated to maternal BMI or heights), an improvement in socioeconomic status and living conditions, and reductions in poverty and better provision of, and access, to health care and education.

Once these bigger babies are born, however, their growth rate is slower than babies of previous generations resulting in a convergence of size at the age of 1 year. This observation further strengthens the hypothesis that it is something about pregnancy, not babies, that has changed.

Another possible downside of increased neonatal size is that a bigger baby may be more likely to outstrip a placenta’s oxygenating capacity making that baby more vulnerable to distress in labor or stillbirth. The US stillbirth rate has not risen; indeed it has gone down, but that has happened in parallel with a dramatic increase in C-section rates and induction rates, allowing for rescue of babies that would otherwise die.

The hypothesis that improved nutrition has made childbirth more dangerous is speculative, of course, but it could explain a lot of observations that confound midwives and other natural childbirth advocates. It explains why intervention rates have risen: pregnancy itself has become more dangerous to both mothers and babies. It explains the results of studies like the newly published ARRIVE trial that showed that inductions not only improve outcomes but lead to lower C-section rates (a 39 week baby is both easier to deliver and less likely to experience fetal distress than a 40, 41 or 42 week baby). It may also explain why we are hearing more about postpartum pain, incontinence and discomfort during sex and long term incontinence and pelvic prolapse.

Who could disagree with the idea of improving nutrition for pregnant women? No one, but that doesn’t mean it isn’t an intervention. And it’s an intervention that may have made childbirth more difficult and dangerous — a consequence we haven’t considered because other inverventions have allowed us to avoid the potentially deadly results.


*That trend seems to have reversed in the past two decades with babies becoming slightly smaller, but still bigger than one hundred years ago.

43 Responses to “Has improved nutrition made childbirth more dangerous?”

  1. Sarah
    August 20, 2018 at 11:16 am #

    Yeah, keto seems to work brilliantly for some people and not for others. I find I’m still hungry when I have no carbs at all, meaning I’m just going to end up eating crap. Better to cut down altogether. I definitely do better when I don’t eat much sugar though.

  2. Cynthia
    August 20, 2018 at 7:28 am #

    To be fair, some of this isn’t really about nutrition per se – it is also about the fact that most peopls can get sufficient calories even if they are poor, but those cheap calories may be low in other nutrients and levels of diabetes are higher.

    • EmbraceYourInnerCrone
      August 20, 2018 at 9:47 am #

      Also if one lives in a food desert (because that’s where you can afford to rent) and relies on public transportation, one has fewer sources of fresh fruits and vegetables and fish or lean meats. Canned is an option but cans are also heavy (can you tell I’ve had to haul groceries and a baby on the bus…) Granted it was years ago but I still remember trying to work out the logistics.

      • Cynthia
        August 20, 2018 at 12:16 pm #

        Exactly. 100 years ago, someone who was malnourished may have also appeared to be underweight. Today, most people in North American have access to enough calories, but access to fruits, vegetables and proteins in more expensive and isn’t as easily available everywhere. For those who are susceptible to diabetes, a high carb diet increases the risk, and that’s associated with larger babies. So yes, it’s great that people aren’t actually starving, but it’s not quite a matter of a simple trade-off between good nutrition and more difficult births. It’s sometimes more like “enable all women to access decent food, and some problems will decrease”.

  3. PeggySue
    August 11, 2018 at 4:44 pm #

    Gah. Nutrition. And lack of science. So I have a friend who got into a rut of eating lots of junk food, too much at each meal, and not exercising a lot. He found himself with heartburn, fatigue, trouble sleeping, etc. So what did he do? He went on the ketogenic diet, and now he’s a True Believer, because he lost 20 pounds and all his symptoms are gone!!!! It’s virtually impossible to bring pot luck food for someone on that diet, really. What annoys me is that, as a young man, he probably could have lost the same amount of weight by simply cutting back portions a little and quitting dessert. But NOOOOOO, he has to be having Reactions to All These Things, so he Has to Eat this Keto Diet. Color me Intolerant Old Fogey.

    • The Bofa on the Sofa
      August 11, 2018 at 8:21 pm #

      Yeah, I’ve lost about 15 lbs since April, without any stupid “ketogenic” diet crap.

      My secret? I’ve cut out candy, cut down on Mountain Dew (but haven’t cut it out completely) and have been running 15 miles a week on the treadmill.

      And of these three things, the last one is most important (although the “no candy” thing will be a much more important factor come valentine’s and Easter seasons. I used to eat a lot of bags of cinnamon jelly hearts and jelly beans (like, 6 bags of each) every year)

      I still eat my share of noodles and bread.

      Diet, yes, some. And exercise. Wow, call me radical!

    • demodocus
      August 12, 2018 at 8:57 am #

      My husband lost about that when he simply cut out soda and chips for 6 months.

    • EmbraceYourInnerCrone
      August 14, 2018 at 11:18 am #

      Can I come sit by you? I am overweight due to to much love of sugar, too much eating out or eating on the run due to work demands and lack of exercise. I have started changing my diet as I find “dieting” unsustainable. I stopped eating candy and soda especially at work (departmental candy dish needs to go away!) a few months ago, I stopped ordering appetizers when I do eat out and I refuse to feel guilty for not finishing the huge amounts of food that are restaurant portions (I just take them home for left overs). It’s working but really slowly.

      I need to work on walking a lot more but am trying to at least do something every day – I use the ladies room on the third floor because that forces me to walk up and down the stairs. My friends who keep trying weird supplements and weird “super food” or Keto diets drive me nuts. Plus isn’t keto dieting dangerous for your kidneys ….

  4. Sue
    August 10, 2018 at 11:06 pm #

    One of the things happening here, which is repeated in the discussion of many health issues, is that we talk about the down-sides of better nutrition (obesity, type 2 diabetes, large babies and obstructed labor) without talking about how these have replaced the disadvantages of poor nutrition (in our wealthy societies).

    They are well-described here:
    Epidemiologic Reviews 2010
    Maternal Nutrition and Birth Outcomes
    Full paper at:

    So, yes, we have bigger, heavier people, but we have less rickets, anaemia, smoking-affected babies and general risks associated with malnutrition.

    When the risks of plenty replace the risks of starvation, there are some losses but also many gains.

    • Gilad
      August 14, 2018 at 8:54 am #

      My oldest was IUGR and SGA, weighing 2400 g born at 37 weeks + 2 days. He is now 3,5 years old and and at a low but within- the- normal- range- weight. He has ASD and probably some learning disabilities. So far he has been physically completely healthy. I never smoked or drinked and during pregnancy I continued to live my normal pretty healthy lifestyle. I just didn’t gain much weight. Although I know with my mind that he most likely has ASD for genetic reasons I feel guilty to the bottom of my heart for him being born obviously malnourished and maybe suffering long term consequenses. Reading the article in the link makes me worry even more. I just feel so bad and everytime I read or hear about birth weigth related articles I go out of my mind 🙁

      • fiftyfifty1
        August 14, 2018 at 10:44 am #

        “I never smoked or drinked and during pregnancy I continued to live my normal pretty healthy lifestyle. I just didn’t gain much weight…I just feel so bad..I go out of my mind.”

        That is The Mom Guilt Monster trying to bully you. It tries to latch on to a lot of women when they become mothers. It exploits our deep love for our children and tries to trick us. But you can tell it to go away! (you may have to tell it many times, but keep telling it.)

        Here’s a reality check: Dr. Amy’s post is about how copious food/nutrition can cause babies to be bigger than normal, it’s NOT about the causes of IUGR. Drinking and smoking can for sure cause IUGR, but “I just didn’t gain much weight” doesn’t. I was like you, I had trouble gaining weight in pregnancy (and I was small to begin with.) For my first baby I went home from the hospital weighing less than I had before I got pregnant. Baby #1 was good size anyway despite being born at only 38 weeks. The second pregnancy I worked hard at weight gain and did much better than with the first pregnancy. Despite that, baby #2 was borderline SGA/IUGR. Why? The placenta had calcified for unknown reasons. IUGR is not about what we do, it’s luck (except in cases or drinking and smoking.) And autism is luck too.

        So tell that Mom Guilt Bully to fuck off. Seriously, keep telling it. It’s NOT your friend and it’s NOT your boss.

      • MainlyMom
        August 15, 2018 at 8:40 pm #

        Don’t feel guilty! It wasn’t your fault or anything you did. Hugs.

      • Cynthia
        August 20, 2018 at 7:23 am #

        One message that really doesn’t get around enough is that you can follow every recommendation and do everything right, and STILL end up with problems in a pregnancy.

  5. yentavegan
    August 10, 2018 at 6:15 pm #

    THis feels true….My newborns were on average 3 pounds heavier than my mother’s …and yes I needed c/sec’s to get 2 out of 5 babies born.

  6. August 10, 2018 at 3:44 pm #

    There’s one other trend I’d like explored before deciding – the rate of C-sections compared to birth weight of infant over time.

    I used the example of birth weights in human as an example of stabilizing selection when teaching HS Biology. Most babies weigh in between 5-8 pounds because they are mature enough to survive but small enough to be born vaginally. A 3 pound baby has immature organs due to lack of food, maternal illness, or genetic abnormalities. A 12 pound baby, on the other hand, is unlikely to be born vaginally and will die during labor.

    Like a lot of human interventions, C-sections beget more C-sections. Having vaginal birth as the only option places a strong selection pressure against large babies as well as a pressure against certain maternal pelvis shapes. Adding safe accessible C-sections greatly reduces that pressure since the upper limit for large babies depends on things like their ability to regulate blood sugar after birth after being born to a GD mom – so now 9-11 pounders aren’t selected against as hard as a 13-15 pound baby.

    • swbarnes2
      August 10, 2018 at 4:14 pm #

      But we’ve only had common C-sections for about 100 years. I don’t think that’s enough time for evolution to have really changed the % of women with dangerous large babies. Diet and nicotine exposure have changed far more drastically in that time.

      • August 13, 2018 at 12:42 pm #

        Evolution can work very rapidly especially when a strong negative driver is released. Malaria in the US has only been controlled for around 100 years – and that’s been long enough to lead to changes in the genetic frequency of sickle-cell trait in African-Americans compared to areas of Africa where malaria is endemic.

        If babies are responding dramatically to the changes in diet (which have occurred in less than 100 years) and nicotine (which went from very low for women in the early 1900’s to highly prevalent in the 1950’s back to very low now) both of which produce relatively mild evolutionary forces, why would access to safe C-section which has a large direct response on the number of surviving children a woman has show a weaker response?

  7. fiftyfifty1
    August 10, 2018 at 1:18 pm #

    Yep. You can see it in the progression in my own sibling set. Each of us sibs weighed more than the last to the point that my youngest sib weighed nearly 3 full pounds more than my oldest sib. Turns out that a teen nullip who starves herself, hides her pregnancy and smokes will produce a very different size term fetus than that same woman now a multip in her 30s who is living an optimally healthy lifestyle. (And turns out that a sub-6 pound baby is a faster easier birth than a nearly 9 pound baby, even taking into account parity.)

  8. Sheven
    August 10, 2018 at 12:48 pm #

    This is an interesting idea, and it allows me to ask a question about another interesting idea. I recently read part of a book called “Nourishing Diets” by Sally Fallon. Supposedly it is a response to those “paleo” claims, looking at old research describing what non-industrial and, for the most part, non-agricultural tribes actually ate. This part was very interesting.

    The problem was the author takes that and then claims that tribes had no dental problems (they did, there are skeletons dug up by archaeologist with no teeth or bad teeth) low rates of cancer, of heart disease, and then the author implies that learning disabilities, asthma, allergies, and pain in childbirth are modern health problems because of diet. It is about the time that she said that breakfast cereals like cheerios were “possibly toxic” because they processed the grains at high temperatures that I put the book down in disgust.

    However, the theory in the book, that as far as I can tell relies on the research of a dentist from the 1930s, says that paleo-living tribes had wider skulls and wider hips because of their diet and that meant little or no pain in childbirth. Response?

    • fiftyfifty1
      August 10, 2018 at 1:06 pm #

      Total Bullshit.

    • Heidi
      August 10, 2018 at 1:28 pm #

      My anecdotal response is it wasn’t my hips that hurt. It was my vagina being ripped apart and the contractions during labor that hurt. I think I have fairly wide hips. Baby had no problems going through my pelvis and labor was pretty quick. But it hurt.

    • FormerPhysicist
      August 10, 2018 at 1:50 pm #

      I’m pretty sure that dental abscesses were a leading cause of death. Low rates of cancer – lol. Cancer is primarily a disease of age. Population-wise, there isn’t much cancer until people aren’t dying first of other issues. I think heart disease is rather similar.
      For example, when I look at my maternal genealogy, almost every woman dies of breast/ovarian cancer. Except for the very large percentage who died of childbirth, diseases, accidents, and war.

      • maidmarian555
        August 10, 2018 at 3:09 pm #

        10 years ago I would have said that we don’t have a history of breast cancer in my family. Two of my aunts have had it in the last couple of years- one was in her 80s, the other is in her 90s (they both got treatment that was successful and are still going strong).

        • Abby
          August 11, 2018 at 3:56 am #

          That’s not a family history is it though, it’s age related cancer, most people will get cancer if they live long enough

          • maidmarian555
            August 11, 2018 at 2:58 pm #

            Well yes, that was the point I was making. Paleo woman didn’t die of breast cancer because she didn’t live to 90; she would have been considered really old if she even made it to 40. And it’s certainly a nonsense that said cancers are caused by eating toxic breakfast cereal and not following the same diet that Paleo woman would have eaten. However I do belive it is useful to know that if I live to a ripe old age, I should certainly be alert and check my breasts regularly. Routine screening is only done here in the U.K. until you’re 70. That two women in my family have developed breast cancer well after that is probably a reasonable indication that I should be vigilant too if I’m fortunate enough to live that long. And certainly for my daughter, as it’s on the paternal side also (my MIL has been treated for the same cancer in her 70s). So yes- age related cancer certainly. But that the age-related cancer in my family has been breast cancer is still relevant to some extent I think.

    • demodocus
      August 10, 2018 at 3:41 pm #

      A dentist claiming to know anatomy? That’s got my skeptical radar going.

      • Petticoat Philosopher
        August 10, 2018 at 11:21 pm #

        Check out the Weston Price Foundation website (her organization) if you want to jump down a seriously weird rabbit hole.

        • demodocus
          August 12, 2018 at 8:47 am #

          No thanks, I’m busy pretending Rusty Rivets and Paw Patrol are helping Thomas get off that cliff after the track broke. Seriously, how often do tracks break on Sodor?! Do they make the rails out of ceramic?

          • Petticoat Philosopher
            August 12, 2018 at 10:33 am #

            I guess they’re kind of like the shields on the Enterprise.

        • August 13, 2018 at 3:37 am #

          I think my favorite story by a WAPF blogger was explaining how raw butter cured a cavity in her son’s tooth. Cured it. Made the tooth grow back. Okay.

          • Petticoat Philosopher
            August 13, 2018 at 10:59 am #

            Oh, there are lots of those stories. “Remineralizing” teeth is a big trope with them.

            I know way too much about this group but I do really find it fascinating. They’re probably my “favorite” dangerous pseudoscience organization.

          • August 13, 2018 at 1:44 pm #

            Uhhhh. Exactly how does one replace lost tooth enamel, pulp, etc with fat? I mean, I am second to no one in my love of butter, as long as it’s understood to mean “tasty ingredient” and not “magic medicine.”

          • FormerPhysicist
            August 13, 2018 at 2:32 pm #

            Dangerous idiots.
            Science is way cooler, though. https://www.sciencealert.com/alzheimer-s-drug-could-be-used-to-regrow-teeth-six-weeks

          • Heidi
            August 13, 2018 at 11:56 am #

            Yes, those. Supposedly the dentist was shocked but had to admit it did happen. Yet this dentist doesn’t manage to tell his colleagues about this and mainstream dentists are still push brushing with fluoride and flossing. Cause I guess a conspiracy by big toothpaste?

        • Who?
          August 13, 2018 at 3:56 am #

          I made the mistake of looking at this website. The anti-vax is strong with that one.

          And they had a whole feature on the benefits of black salve.


          • Petticoat Philosopher
            August 13, 2018 at 10:57 am #

            Name some horrifying woo, they’re for it. Their pregnancy diet recommendations sound like they just looked at what real doctors recommend and said “Do the opposite.” Unpasteurized milk, huge amounts of retinol from food (they deny that “natural” vitamin A causes birth defects af high levels, only “synthetic” supplements), and they strongly discourage pre-natal vitamins.

    • RudyTooty
      August 10, 2018 at 7:03 pm #

      Oh Sally Fallon!

      This is code, among some of my friends and I, for foodish cultishness.

      When we do something absurd, like add a 1/2 c of butter to our broccoli, we’ll say “Sally Fallon says this is good for us!”

      I even own her damn book, because I cavort in those types of hippie circles.

      The variety food restrictions at our potlucks are ridiculously restrictive and oppressive. I tend to bring gluten AND processed meat AND refined sugar. Preferably all in the same dish, just to be a subversive ass.

      I’m sure my potluck dish is creating all sorts of non-birthin’ hips.

      • Sheven
        August 10, 2018 at 11:32 pm #

        I am also hip deep in foodies and health nuts, so a lot of it sounded just like normal, if faddish, health food jargon until every now and again she’d drop in a crazy claim.

    • Petticoat Philosopher
      August 10, 2018 at 11:17 pm #

      Oh, trust me, you haven’t even begun to scratch the surface of Sally Fallon’s crazy. She basically believes that “perfect” nutrition (defined as a diet including copious animal fat, unpasteurized milk and huge doses of vitamin A from liver and cod liver oil among other things) can create ubermenschen who are intellectually and physically superior to the rest of the plebes’ children (who have had refined sugar pass their lips) and who never get sick. (Unless they’re vaccinated or have had antibiotics at some point. Those things are evil and all bets are off then. But you can fix it with more grass-fed butter and foie gras!)

      She really goes hard on pregnant women too. If your child is born less than perfect it’s definitely because your pregnancy diet didn’t follow her rules. Or maybe because your nutrition as a child didn’t, in which case it’s your parents’ fault. Or maybe you took birth control pills and it’s a miracle you got pregnant at all!

      She also has an incredibly creepy obsession with “prefect” bone structure (wide faces which is apparently the best kind of face because that dentist in the 30s said so). She gets it from the single source text of her food cult, which was published during a time when it was still acceptable to talk about arbitrary differences in human physical features as if some were objectively superior to others. (This was in the 30s. Some, uh, things happened in the world after that that made that kind of talk demode but she and her followers are sticking to their guns.)

      I know way too much about her because she’s sort of loathsome as fascinating at the same time. They don’t just peddle fake natural science but also fake social science and imagined, idealized history and, as a social science person, that kind of thing is incredibly interesting to me, even as it also infuriates me.

      • Sheven
        August 10, 2018 at 11:30 pm #

        Huh. I picked it up because I thought it would be more about history and tapped out after the first couple chapters. Interesting to realize I was reading cult literature.

        It was weird because a lot of it sounded good–cream and dairy, organ meats, balanced diets–and then all of a suddenly you’d be like, “Eh, I’m not sure about diet causing asthma or allergies. Wait. Did she just say that learning disabilities are the result of diet?” And then it would be a long interesting section on how Australians invented fishing machines and burned the land to encourage the plants and animals they wanted. And then, “Wait, why is processed food bad, but grains that are processed through soaking and sprouting and washing and cooking and grinding are good? Extruded wheat cereals are *toxic*?”

      • PeggySue
        August 11, 2018 at 4:46 pm #

        Feh. I took cod liver oil, more than I wanted, as a kid. Didn’t do jack.

      • AnnaPDE
        August 13, 2018 at 11:22 am #

        At least the diet she’s peddling without a scientific basis sounds a lot more enjoyable than the usual cabbage soup, quinoa and kale. I’m all up for a “Tournedos Rossini Detox”, purely for health reasons of course.

Leave a Reply

You must be logged in to post a comment.