Mommy brain

or Why baby smiles are like crack

My husband and I had little — meaning no — baby experience before bringing our daughter home. We would jokingly ask questions like “how much do we have to feed this thing?” and then nervously laugh, look at each other with concern, and consult the “owner’s manual” (our affectionate name for the American Academy of Pediatrics tome).

the Owner’s Manual

And then, she was born. An insane flurry of eat, poop, soothe, repeat.

After those first few weeks, when the dust settled, I had a profound revelation — I might actually know what I’m doing! Could I now have maternal instincts that were not there before?

By its very definition, “instinct” is a response that is inherent, basic, not requiring thought or careful consideration. Unlearned. Unconscious. Instinct. [Note: maternal instinct makes sense given that we have yet to see a National Geographic film of a baboon parenting class gathering every third Tuesday on the savannah.]

Turns out, there is quite a bit of evidence demonstrating that our brain does, in fact, change when we transition from clueless pregnant woman to caregiver.

As pointed out in a 2012 review in Physiology and Behavior, this transition marks an important point at which our brains have to shift from a world revolving around self-care to one oriented around the care of a tiny helpless being. With a little bit of parenting experience, the mammalian brain shows changes in cognition (e.g. spatial memory, attention), emotional responsiveness (e.g. boldness in new settings, focus), and social awareness (e.g. attention to those helpless little beings). Put a pregnant rat in a cage with pups strewn about, and she doesn’t give a shit. Put a mama rat in a cage with pups strewn about, and she goes right to work, gathering up those babies, protecting and nurturing them.

Now, it probably helps that the mama brain is also altered to respond to baby with a spurt of sweet sweet dopamine right in the reward centers of the brain, similar to a hit of cocaine.

Yup, our babies are addictive.

As demonstrated in a 2005 paper in The Journal of Neuroscience, a mama rat with a suckling rat pup feels the same dopamine reward signal as a virgin rat given cocaine. Interestingly, though, in the mama rats, a dose of cocaine does not have this same effect and actually suppresses activity in the reward center. Nature’s way of focusing mom’s attention — You want to get high? Feed your baby.

The science of baby smiles. Methods figure from Strathearn et al. 2008

But wait, a similar high does not require baby at the teat. In a 2008 study in Pediatrics, researchers using human subjects showed moms pictures of their own baby, or someone else’s, along a spectrum from smiley to distressed (see figure). Those same dopamine pathways were activated in these human mothers, BUT only when they were shown pictures of their own babies, and only when the babies were smiling.

But, c’mon, did you need a scientist to tell you that your baby’s smiles are like crack?

At the end of the day, though, the joke is on us. Evolution has crafted tiny manipulation machines. All those cute baby features — chubby cheeks, big eyes, tiny noses, large foreheads — drive our most basic urge to cuddle and protect. Our brains instinctively respond to “baby schema,” a term coined by Konrad Lorenz, a Nobel Prize-winning zoologist famous for studying imprinting and having adorable photos of baby geese following him around and preening his beard. Even the guy’s guy can’t ignore a cute baby face. Go watch Three Men and a Baby for the not-so-scientific evidence.

Baby schema overload.

If you do want scientific evidence, a 2009 study in the Proceedings of the National Academy of Sciences documented which areas of the brain are activated when non-mothers were shown pictures of babies with enhanced or downplayed “baby schema”-typical features. Using manipulated pictures of babies either made “cuter” or, well, not so cute, the researchers were able to demonstrate that the cuter the baby, the more activated the area of the brain associated with anticipation of reward. The motivational drive to become caregivers to cute little critters runs deep in our animal instincts.

There you have it, humans. We all have a little bit of mommy brain!

Happy Mother’s Day!

Lambert, K. G. The parental brain: Transformations and adaptations. Physiology and Behavior 107, 792–800 (2012).

Strathearn, L., Li, J., Fonagy, P. & Montague, P. R. What’s in a Smile? Maternal Brain Responses to Infant Facial Cues. PEDIATRICS 122, 40–51 (2008).

Ferris, Craig F., et al. Pup suckling is more rewarding than cocaine: evidence from functional magnetic resonance imaging and three-dimensional computational analysis. The Journal of Neuroscience 25.1, 149-156 (2005).

Glocker, M. L. et al. Baby schema modulates the brain reward system in nulliparous women. Proceedings of the National Academy of Sciences 106, 9115–9119 (2009).

Next Story — The probiotic bandwagon
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The probiotic bandwagon

Get your baby on board?

Ah, probiotics. The supplement du jour.

It was only a matter of time. Just as we started wrapping our heads around the concept of consuming “live cultures” for gut health, the market spilled into the realm of baby products.

Would you deny your baby something that promises eternal tummy happiness?

What are probiotics?

Is it me, or are probiotics one of those things that we nod our head in conversation and go “oh, sure, totally, it’s soooo important” without having a freaking clue what we are talking about?

Here’s a super quick summary of our belly bugs —

We eat stuff… let’s say kale. Our measly human machinery cannot break down the tough bits in kale. We simply do not have the tools.

You know who does have the tools? Bacteria. Specialized little worker bugs that hang out in our intestine with their tools all ready for the kale chunks that escape our ill-equipped stomach.

In exchange for room and board, those little worker bugs break down that kale and kick back some nutrients we would have missed. Kale-eatin’ bugs are only the start. Along with a range of other little bug friends, our gut is host to a beautiful little ecosystem that, when kept happy and in balance, can confer all kinds of health benefits.

Mmmm… bacteria.

Probiotics? Anything that you might ingest containing live microorganisms (bacteria) that pass through the digestive system to confer “benefits” once they reach the intestines. For example, a whole range of yogurt products have “live cultures” on board and are promoted as probiotics.

Here’s the problem — our gut is already jam packed with resident bacteria. After those “live cultures” brave the digestive passage to end up in your gut, they drop off the good stuff they already made while waiting out in the yogurt, and pass on through. The real estate landscape is already too crowded and the residents are not likely to make room for the new guys.

But you know whose gut does have a lot of open real estate?

Colonizing the baby gut

In order to establish residency, the microbes have to get there.

When they’re born, babies are rubbed all over by bacteria that may be important for gut colonization. The gut of a C-section babies compared to a vaginal birth babies shows profound differences. Babies that come out on their own have higher quantities of helpful microbes. Presumably, this is a result of spending time in the birth canal. But, this study cannot rule out another possible influence — C-section mamas went through major surgery and weren’t able to nurse immediately or effectively for the days before the test (samples taken on day 3 post-birth).

All aboard!

Which brings us to that mama milk. We all know that breast milk passes along important antibodies, but here’s another thing that breast milk may provide— gut bacteria. Yes, helpful microbes may also be passed along in the milk.

More importantly, human breast milk contains a critical prebiotic to sustain the helpful bacteria.

Prebiotics are more important than probiotics

Ok, prebiotics, what are those?

Think of prebiotics as the food for the good bacteria. Without a prebiotic, the probiotic bacteria reaching the intestine realize that there is nothing for them to do and nothing for them to eat, and they wave goodbye to the other bacteria setting up shop and head on out the other end. They are probably not around long enough to confer any kind of benefit to that baby.

No food? No bugs.

Human breast milk has special complex sugars, called Human Milk Oligosaccharides. The human body cannot digest these sugars. Only specialized bacteria can digest them. By introducing this prebiotic, the bacteria that feast on this specific sugar flourish. They set up shop and multiply. They also kick back amazing benefits — immune system building, preparing a happy gut for adulthood, and the list goes on.

But these bacteria will only set up shop if they have those special mama sugars available. No sugars? No food. No bugs.

You can have a prebiotic without a probiotic, but a probiotic without a prebiotic is useless.

Adult side note:

Be sure to wash it down with a glass of breast milk.

One funny thing about this all is that a common probiotic on the market is a little posse of bacteria called Bifidobacteria. These bacteria were first isolated from baby poo and now they are the main health bug in a whole range of probiotic products aimed at adults.

The problem? Bifido prefers Human Milk Oligosaccharides as a prebiotic. Since I’m pretty sure no adult is taking a healthy swig of breast milk on a daily basis, it’s hard to say how much benefit our adult gut is getting from adding these fellas to our daily diet.

Back to the babies! The verdict?


First, here are my general concerns —

One, you are essentially feeding your baby bacteria. Where is this bacteria coming from? How is it controlled, isolated, tested?

Two, the baby gut is trying to do it’s thing. It is set up to do it’s thing. Do we need to play puppet master to a community that has evolved for beautiful symbiotic balance?

So, at first I would have said “NO, crazy!” but upon greater reflection I have softened my stance.

A few scenarios:

Natural birth, breastfeeding mama — why mess with nature? This is my category, and, personally, I will not be giving the wee one probiotics.

C-section, breastfeeding mama — Tough one. We still do not know how important the exit strategy is for setting up the important bacteria. Maybe they could use a boost?

Super early baby, breastfeeding mama — Ok, for this one there are some data. A recent study in a NICU, doctors gave babies born pre-term (< 32 weeks), daily doses of a carefully screened probiotic. There was a significant reduction in necrotizing enterocolitis (a super scary intestinal disease in preemies). Sure, the numbers went from 10% to 5% but when you are talking about babies, every baby counts. The authors conclusion was to adopt daily probiotic administration into the protocol of pre-term care.

See a pattern? Breastfeeding is key. The boobs make the prebiotic.

Even in the NICU study, 93% of the mothers were nursing.

Formula + probiotics?

Only human milk has the one true prebiotic to encourage the happy bugs to grow and establish their community.

Formulating the formula (from: Aptamil with Pronutra+)

To get around this, formula companies have tried to mimic Human Milk Oligosaccharides with a combination of complex, but not as complex, sugars called GOS/FOS for short. Some research suggests that having this GOS/FOS prebiotic is enough to get the happy bacteria established in the baby gut similar to the breast-fed baby (no probiotic necessary). Other research warns that we don’t know enough about GOS/FOS to be messing around with it.

Research on everything involving the baby gut is still in its infancy (pun intended).

We haven’t mapped out every inch of bacterial real estate in the ever changing baby intestine. We don’t know the job description for every occupant. We don’t know the long-term effects of manipulating the landscape.

I say, leave ‘em be for now.

The baby will figure out how to walk.

The microbes will figure out how to flourish.

Next Story — The troubled life of the pregnant back-sleeper
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The troubled life of the pregnant back-sleeper

Beware of the vein crushing uterus

Of all the “no no’s” thrown at your growing pregnant body, the one that I found ridiculously frustrating was the “No sleeping on your back” rule.

Sleep is a precious precious commodity when carting around a huge pregnant belly. Why would you dictate how I sleep with this thing?!

The reasoning for the sleep position policing stems from the idea that back sleeping can choke off your baby’s oxygen supply.

Here is the “logic”:

Your uterus is heavy. So heavy, in fact, that it puts weight on the inferior vena cava, the vein that runs blood back to your heart. A compressed vena cava means decreased blood back to the heart and, therefore, decreased blood coming out from the heart. Less oxygenated blood for you, less oxygenated blood for the baby. Not good.

Clearly, the stock photo models did not get the memo. But, DAMN, she looks comfortable!

I really wanted to call bullshit on this one during my last pregnancy (yet dutifully buoyed myself on my side with pillows each night). I mean, if oxygenated blood is getting cut off, it would affect how that blood gets to the brain and you would feel dizzy. Right? So, isn’t that a simple test to see if your heavy uterus cuts off your blood supply? Lay down, feel woozy, heavy uterus!

Drs Farine and Seaward at the University of Toronto seem to agree with me.

“Women should be told that a small minority of pregnant women feel faint when lying flat” — Dan Farine, MD, FRCSC, P. Gareth Seaward, MD, FRCSC

Of course, my experimental nature was cut short when a friend sent me this article.

Medical student, Allan Kember, is fighting stillbirth with a belt that prevents pregnant moms from sleeping on their backs.

Stillbirth!? Back sleeping!? Holy shit. Maybe this deserves a second look.

I called up Allan.

Allan’s research stemmed from studies like this one and this one. Most inspiring though was a study coming out of Ghana in which the authors showed that a quarter of stillbirths might be prevented by changing mom’s sleep position. Allan wanted to answer the call for a simple, inexpensive solution to reduce stillbirth in the developing world. His thought process: encourage expecting moms to not sleep on their back, save a few babies.


Of course, I had to bug him about the whole vena cava scenario. He admitted that this might not be the full picture.

Another culprit? Gestational obstructive sleep apnea (sleep disordered breathing).

Here’s the problem though: we really do not understand gestational sleep apnea well enough to point a finger quite yet and we have no idea how obstructive sleep apnea might affect a growing baby. Oxygen flow disturbances? Stress responses? Mom snoring too loudly?

Ok, probably not the last one.

At the end of the day, it seems that stillbirth may follow a similar rule as what has recently been shown in SIDS research. It isn’t any one thing that causes it. It’s the perfect storm of complications that can result in stillbirth.

Warland and Mitchell’s Triple Risk model for unexplained stillbirth.

The triple risk:

(1) maternal risk factors, (2) fetal risk factors (low growth rate, placental insufficiency), and (3) a stressor (such as back sleeping).

Don’t tick off all three boxes, you’re in the clear. At risk already? Do whatever you need to do to prevent that third tick and you’re in the clear.

SIDS research has figured out a way to prevent that third tick in as many babies as possible, regardless of preexisting vulnerabilities — the giant, border crossing “Back to Sleep” campaign where parents are reminded to never put a baby to sleep on her tummy. The result? A decrease in SIDS with an increase in flat heads. But flat heads are fine if it means babies keep breathing into adulthood.

Of the 4 possible sleep positions, pregnant women end up on their backs over 25% of the time, with over 80% of women hitting this position some time during the night. It’s normal. It’s common. It’s an epidemic?

Researchers in the UK are now trying to determine if a national campaign, similar to the SIDS “Back to Sleep”, should be launched to tell moms not to sleep on their backs.

This is where I draw the line.

Going to sleep with a homework assignment (“do not sleep on your back!”), is enough to keep us pregnant moms up worrying about all the damage we can do to our unborn child while we toss and turn. One study showed exactly this — asking women to make sure they slept on their left sides resulted in decreased overall sleep time.

When quality sleep is so freaking important during pregnancy and so freaking difficult to achieve, why mess with it more?

Here’s another gem of a quote from Drs. Farine and Seaward:

“If lying prone had been detrimental to a normal pregnancy, the species would long ago have ceased to exist” — Dan Farine, MD, FRCSC, P. Gareth Seaward, MD, FRCSC

Back to the stillbirth thing. Maybe the first thing to tackle is figuring out how to define which women and babies are at risk and come up with solutions for this small subset. Maybe it’s a CPAP to treat sleep apnea, maybe it’s a belt with balls to encourage side sleeping, maybe it’s a mound of body pillows.

For now, it’s time for me and my big, heavy, vein crushing uterus to hit the hay.

Next Story — 7 things I learned during my pregnancy
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7 things I learned during my pregnancy

Finding the science amidst the bullshit

Pregnancy is truly an amazing thing. You grow a human from scratch. You grow a new organ from scratch. And at the end of it, your body involuntarily starts to flex a muscle you barely thought about until it kicks into high gear to squeeze that tiny human out into the world. Crazy.

If this isn’t enough, pregnant women are living in a time when everyone loves to freak them out. I realized early on that websites and advice pages and comments sections are horrible places to visit while attempting to navigate the best way to have a healthy and happy womb baby. So, I started doing my own research.

I wanted to come to a logical conclusion based on science rather than the anecdotal “well, my sister’s cousin-in-law totally ate banana leaves every day for a month and her kid was walking by two months”.

I’m a physiologist by training. I can use the salutation “Doctor”. But I am not an M.D.. Just a curious Ph.D. who got knocked up (on purpose) and trusts in science. These are some conclusions I came to for myself.

Eat the cheese. Seriously. Eat it.

Why would anyone want to deny a pregnant woman delicious cheesy goodness? I heard about this “no-no” long before I even thought about harboring a small human in my baby oven.

A barely pregnant colleague at lunch asked a waiter “Is there cheese on that salad?”

Waiter: “Yes, there is goat cheese”.

Colleague: “Oh, never mind, I’m pregnant”

Me: “What? Seriously?!”

Not even born yet and baby is spoiling all the fun. (yes, I do actually consider having the ability to eat any kind of cheese the epitome of fun).

So, what the hell? The thinking behind this “no-no” is that soft cheeses may be unpasteurized and, therefore, potentially contain Listeria monocytogenes, a bacteria that causes Listeriosis. Listeriosis can cause all kinds of horrible things to happen to a womb baby. But, c’mon, let’s be realistic here. What are the odds that the chunks of goat cheese on the salad are actually going to lead to disastrous consequences for your unborn child?

First, the cheese is probably pasteurized. Raw milk is banned across most of America. Twenty-eight states allow it to varying degrees.

Did this restaurant really smuggle cheese across the border or source a specialty cheese-monger just to decorate an $12.99 spinach salad?
Fresh goat cheese straight from the cheesemaker in France? Yes, please!

Second, the odds of Listeria creeping around in raw milk is insanely low.

A study analyzing a 13 year data set found a total of 73 disease outbreaks caused by non-pasteurized milk products. Three of them were from Listeria. THREE. And I think these cases were actually from a family in Texas who made queso fresco from the family cow. I’m not kidding.

What my pregnant colleague should actually have been worried about was the spinach, not the goat cheese. So, hey there, FDA, let’s legalize unpasteurized cheese and make spinach illegal!

You are NOT off the hook for litter duty.

Collective sigh of frustration from the pregnant cat owners out there hoping to subject their partners to nine months of litter duty in exchange for nine months of designated driving. Sorry!

There is a possibility that lurking inside kitty poo is a parasite called Toxoplasma gondii. The resulting infection, toxoplasmosis, is another illness you want to spare a pregnant woman due to its terrible consequences for the womb baby.

But, here is what would have to happen in order for you, pregnant woman, to get toxoplasmosis from cleaning up after Mittens:

Do not trust this face.
  1. Mittens goes outdoors.
  2. Mittens eats a rat infected with toxo.
  3. Mittens comes back inside and poops in his litter box.
  4. You clean out Mittens’ litter box.
  5. Somehow (I’m not judging), you ingest that poop.

You really need five out of five of the above to become the parasite’s new home. And if you have already been infected in your lifetime (I’m looking at you, kid who ate mud pies in the sandbox. Oh wait, that’s me), the chance of a second round of toxoplasmosis goes way down.

If Mittens is a lazy, non-mousing cat and you practice normal person hygiene and wash your hands after you scoop poop, you are probably in the clear.

Get scooping.

Enjoy your morning cup of joe.

I actually got a “tsk-tsk” look from a salesperson in the maternity section of Gap for carrying a cup of coffee.

“It’s empty!” I exclaimed.

Still unsatisfied with that response, I corrected myself “It’s decaf!”.

It wasn’t. But the answer was accepted with a smile.

Coffee is fine… in moderation. Research on caffeine falls into that tricky category of how do you do an experiment on pregnant chicks? You can’t exactly do a direct cause and effect type of experiment — “Here you go, woman hoping to have a healthy baby, drink five cups of coffee a day so that we can see if your bundle of joy arrives a month early, only reaches 4’8”, and will need serious ADHD medication to sit through an exam when he’s ten.” Not the most ethical study.

Instead, most studies rely on gigantic data sets and relatively subjective classifications of caffeine drinkers. Consistent, it is not.

One thing that falls out, though, is this: one cup of coffee is not likely to have any effect on how long the baby cooks, how big the baby is going to be, or how hyperactive the kid will turn out.

Two cups probably ain’t so bad either.

Don’t worry, placentas move!

When I was 20 weeks pregnant, we were told I had a “low-lying placenta”. It was too close to the baby’s exit and could cause potential complications later. I was told it might shift upwards when the uterus expands but if it was still in the way of at the end, I might need a C-section.

The baby was healthy but I still felt a bit defective — this newly sprouted organ decided to grow in the wrong place. Fantastic.

Trying to figure out the likelihood of the whole “it might shift upwards when the uterus expands” claim from the sonographer, I wanted to know if there was any scientific reason behind a magical moving organ. Not only is there scientific explanation for all of this but it is more mysterious and crazy than I had even expected.

Yes, they move!

The placenta can actually migrate up the uterine wall as pregnancy progresses. Yup, a slow crawling bag of blood. Super cool.

There are two concepts as to how this actually occurs.

Dynamic placentation suggests that the placenta is constantly forming and reforming attachments to the uterine wall. The bottom of the uterus is stressed the most during growth, making this region a less desirable spot to set up new connections. The best real estate to aim for? Higher ground.

Trophotropism suggests that the placenta actively seeks the best maternal blood supply — like plants growing towards sunlight (phototropism). Again, the best blood supply is up higher where the uterine wall is thick and juicy.

Placenta art. Just because you can, doesn’t mean you should.

Mine did end up migrating out of the way.

Excellent work, placenta, excellent work.

Unless you are competing in the Olympics, you can run

There is a magical number that floats around when discussing pregnancy and exercise.


This is the number of beats per minute that you are supposed to keep your heart rate below when exercising with a womb baby.

But this number appears to be completely outdated. It was actually nixed by the American College of Obstetricians and Gynecologists TWENTY years ago.

Of the various studies looking at the effects of exercise on womb babies, only one found anything resembling an effect.

The only effect of exercise? Fetal heart rate may slightly elevate if you are a pregnant, endurance sport Olympian pushed to 90% of your training capacity.

Judging from the sample size, there are six of you in the world willing to even try this sort of thing. The rest of you are probably in the clear.

Of course, this may be woman specific and I would still trust the advice of a doctor who knows a woman’s exact condition BUT the science suggests that there is no problem with breaking a sweat with a baby bump.

I would still follow the advice that if you are overheating, bleeding, puking, and/or passing out, stop exercising. But, seriously, do you really need to hear that from me?

The glucose test is kind of bullshit

I will not argue against the importance of diagnosing Gestational Diabetes Mellitus (GDM), but I do feel that the current standard for diagnostics is a bit off.

Specifically, I am calling bullshit on the test that the International Association of Diabetes and Pregnancy Study Groups (IADPSG) is trying to get everyone across the country on board with. This test requires a pregnant woman to go in one time, down a goopy bottle of 75g of flavored glucose straight up, and get her blood drawn twice over two hours.


Now, I am not calling bullshit because I had to take this test and was forced to drink orange flavor and we all know that orange is the WORST artificial flavor on the market. No, I am actually basing this assertion on a statement issued by a panel of experts put together by the National Institutes of Health.

After thorough research, the panel noted that this test has a tendency to over-diagnose gestational diabetes — diagnosing 15-20% of all pregnant women!

This is most likely due to the inherent variability in blood glucose measurements — taking the test on Monday may yield a different result than taking the test on Thursday.

Since there is little solid evidence for the benefits of directly treating gestational diabetes, the risk of overdiagnosing is actually a serious concern. As stated by the panel “overdiagnosis of GDM may lead to the ‘medicalization of pregnancy’ which transforms an otherwise normal pregnancy into a disease”.

It’s bad enough to make us drink orange flavored sugar water, but labeling a perfectly healthy pregnant woman at risk for GDM and putting her on high alert about her sugar intake (at best) or making her more prone to the medical intervention spiral towards C-section (at worst), is bullshit.

American women are being deprived of an awesome labor pain option

So, it turns out that there is a cheap, convenient option for handling labor pain that you have probably never heard of in the context of a delivery room. With widespread use across the globe, a very high satisfaction rating from laboring women, and very low side effects and complications, it is a wonder that this tool is only found in five hospitals in the United States.

What is it? Nitrous oxide. Yes, “laughing gas”.

A 50:50 mixture of nitrogen and oxygen, N2O is short acting and self administered — the woman chooses when she needs a small hit by simply raising the gas mask to her face and inhaling. Quite a contrast from the other option of having a giant needle stuck into your back to hook up a drip system alongside your spinal column.

While it doesn’t eliminate pain quite like the epidural, it has been shown to give a “sense of relief”. I am guessing it also provides a sense of control. Now that I am on the other side of the birth process, having labored completely drug free,

DAMN, I wish I had had that N2O option.

Contractions hurt like hell but if you have a sense of control over that pain, whether real or imagined, the stress of the oncoming mack truck that is a wave of contractions would be a bit easier to handle.

Time to demand it, ladies!

Perhaps the biggest lesson I have learned coming out on the other side of the crazy pregnancy thing is this:

At the end of it all, you have a beautiful tiny human to love and care for… and a million more ways you can screw it up.

Have fun!

(Note: for sources, check out the individual posts in their entirety. Links in the titles)

Next Story — What’s in a due date?
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What’s in a due date?

Ah humans, we love predictability.

We love marking big dates on our calendar.

Impending life changing dates such as the arrival of a tiny human from womb to world?

Please, dear god, give me a date for that!

During my first pregnancy, with the sun setting on my “due date” and no labor in sight, I sat down to address my over-the-top fear of a post due baby and crunch some numbers in a desperate attempt to re-predict the incorrect prediction.

I did not deliver on the “due date” assigned to me in my charts. My daughter came five days late and she might as well have been holding a sign that read “yeah, I was ready today, not five days ago”.

I am not alone. The chance of delivering exactly on that magically assigned day is very rare — only 5% of women deliver on their due date.

So, are we just really bad at predicting when babies come? Or do babies just play by their own rules?

Probably a little of both.

The imperfect science of due date prediction

Fancy a guess?

The art of predicting baby’s arrival takes into consideration several factors — assumed ovulation (based on last menstrual period) and size of the fetus at various stages (assessed via ultrasound).

A study looking at nearly 20,000 births comparing these traditional methods found that precise prediction simply does not exist. Regardless of which method was used to determine estimated Date of Birth, the actual Date of Birth showed considerable variation between babies (up to 2 weeks before, and 2 weeks after). Even with the earliest ultrasound between 11–14 weeks when the fetus is lime-sized, the size of said lime appears to vary just enough to screw up any degree of predictability.

“In terms of implications, expectant mothers should be informed that there is only a 35% chance that they will actually go into labor during the week of their estimated Date of Birth” — Khambalia, et al. 2001

‘Cause babies don’t play by our rules…

Findings from a recent study echoes the frustration of relying on our unreliable fancy tools of due date prediction — of course, we suck at predicting when babies come, babies don’t play by our rules.

The researchers behind this study declared that gestation lengths for normal pregnancies can vary up to 5 weeks. 5 WEEKS! These researchers knew exactly on which day the little egg popped out of the ovary and started its journey to becoming a human. This isn’t your typical “enter last period here” due date calculator. This method represents precision timing at its best.

Since the variation remains quite substantial, it appears that there is more at work than previously expected. Even after the sperm race concludes and genetic material combines, the uterus-bound ball of cells does not follow a consistent trajectory. It can take the fast, direct route, or the slow, scenic route before it nuzzles its way into the uterine lining and sets up shop. The environment that mom provides for the little ball of cells appears to influence this timing. This timing then influences the developmental timeline just enough to throw off how we predict due dates. Essentially, as set within the first couple of weeks, each tiny human can be fast out of the gate or slow. Fast embryos are born sooner.

“events in the first 2 weeks after conception were strongly predictive of the total length of pregnancy, suggesting that the trajectory for the timing of delivery may be set in early pregnancy.” — Jukic, et al. 2013

Comparisons of mom and dad’s birth record vs. their babies further suggest that genetics play an important role. Faster growing babies hit escape trigger earlier than slower growing babies.

But does the trigger respond to the size of the baby or the relative size of the remaining space in utero?

Squished babies may pull the trigger earlier! Short moms (>5’3”) deliver their babies almost five days earlier than their tall mom counterparts (>5’6”). Tall or short dad genes had zero influence over when baby arrived so timing does necessarily depend on baby size. Furthermore babies of tall moms tend to come post date suggesting that just enough extra space may warrant stalled escape plans. Biologically speaking, uterine stretch may have something to do with when and how the body starts the labor process, but more on that another time…

Do Due Dates even matter?

We, as mothers, and fathers, and everyone else who has hounded a pregnant women with the “when are you due?” question expect and crave predictability. We want a due “date”. But our inability to truly understand due dates, and more relevantly, actual gestation length, pose more serious implications than simply placating the curious neighbor.

If we don’t really know what the actual gestation length should be for each specific baby, how do we know who is early, who is late, and who is right on time?

Due dates serve a very important clinical purpose — they provide the information on when to intervene, speed things along, and get that baby out.

This may happen too early, before baby is ready.

That is bad.

Or, it may happen too late.

That is really bad.

A recent study found that baby girls are more likely to have an incorrect, late date assigned and, as a result, are more likely to go post-term with serious consequences.

Since we still need to avoid booting babies from the safety of the womb before they are ready, the researchers suggest a simple solution — keep a close eye on pregnancies in a wider realm of “post-date” and allow mom to have a strong voice in the decision about when to intervene. Always put all the cards on the table:

“…let women make an informed decision about which management they prefer…such a decision would, however, be difficult to make without fully informing mothers about the uncertainties of pregnancy- dating.” — Skalkido, et al. 2010

I suppose it’s time for a big announcement: I am pregnant again.

Baby will arrive sometime towards the end of September.

That’s as specific as I’ll get.

I am boycotting due “dates”.

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