Big Mommies Make Big Babies: Greater Pregnancy Weight Gain = Higher Birth Weight
Here’s a big one for the pile on about gaining too much weight in pregnancy: A new study says moms who gain too much in pregnancy are much more likely to have big babies. And big babies, the author of this study suggests, may be at higher risk of future obesity.
Plus, big babies are harder to get out.
I know what you’re thinking, or at least what I was thinking. How do they know this isn’t just a normal genetic disposition towards bigness?
To isolate genetic factors from the direct result of pregnancy weight gain, the subjects were mothers who had more than one child, and gained different amounts of weight in each pregnancy. The study polled more than half a million women, comparing the birth weights of more than a million of their children.
The results were clear. The more a mother gained, the bigger her baby was likely to be. The results are averages, so there are obviously many, many exceptions on all ends. But the numbers were consistent enough for the study authors to claim a direct relationship between a moms’ weight and her baby’s.
They were even able to quantify this increase:
“every additional kg gained by the mother increases birthweight by about 7·35 g. Infants of mothers who gained 20–22 kg, and more than 24 kg, weighed roughly 100 g and 150 g more, respectively, than did infants of women who gained 8–10 kg.”
That last number would be the equivalent of 17-21 pounds. Which is quite a bit less weight gain than an average woman has been told to aim for in pregnancy. The last person I can remember talking about gaining 17 pounds in pregnancy was Ben Stiller’s wife, Christine Taylor. I also remember her saying her favorite “treat” during pregnancy was cottage cheese and fruit. My mother only gained 17 pounds when she was pregnant with me—by smoking instead of eating.
The study measured for weight gain rather than BMI, which some critics find problematic. There’s also the question of starting weight, which doesn’t seem to have been factored in here. We already know there’s a connection between moms who are overweight before pregnancy and her kids’ weight. So if many of the moms were overweight to begin with, this could have affected the results. It also might explain the 8-10 kg window of weight gain, as overweight women are advised to gain much less weight during pregnancy than average weight women.
I knew that really big babies were at risk of complications and sometimes potential future health problems, this is the first I’ve heard of such a low threshold. The cutoff for “big” here is 8.8 lbs, which while not tiny, doesn’t seem all that gigantic to me. Average U.S. birth weight is about 7.5 lbs.
Interestingly, the average U.S. birth weight actually decreased in 2010, for the first year in almost five decades.
photo: Herkie/flickr
My daughter was 9lb 2oz (although she was born at 41 weeks, and would have been excluded from this study). I gained 40lbs when I was pregnant and some of that weight gain was very deliberate because my doctor told me I was underweight and he said that was more dangerous than being overweight. Stuff like this makes me feel like I can’t do anything right!! I lost all the weight pretty quickly and now that I’m pregnant again, I honestly don’t think I’m going to do anything differently. I’ll eat when I’m hungry, stop when I’m full and not stress out about the scale. But easier said than done when every other piece of research is about how I might or might not be making my baby obese
Laura, I totally agree- these studies can be really stress-inducing! It’s so frustrating (and scary) when you’re advised to do one thing and then a study comes out suggesting that might not be the right thing to do. But it sounds like you are doing everything right.
I think the thing to remember is that studies look at averages, not individuals. A 40 lb weight gain for an underweight woman is totally reasonable. And the fact that you lost it quickly is great. The risks to moms are mostly about pregnancy weight leading to eventual obesity. And I really wouldn’t worry about making your baby obese based on this study alone. This research is part of a broader campaign to help stop obesity. If you have a healthy weight and healthy eating habits, the chances are good that your kids will, too.
Yes i agree with this article! thanks for sharing online!!
Pregnancy Weight Gain
Totally and respectfully disagree. I gained 45 with my first pregnancy and my daughter arrived two weeks after her due date weighing in at 6 lbs 14 oz. With my second daughter, I gained only 35 lbs and she was 7lbs 3oz. My friend who was pregnant at the same time and gained only 20lbs had a whopping 9 lb boy for her first. My sister in law (who is tall like me) always gains 30 – 40 lbs and her babies are in he 6-7 pound range. Maybe it depends on the type of weight you gain. I’m sure if you eat a lot of carbs and sugar, you will tend towards gestational diabetes and your baby will be bigger. I dunno – that is the only possible connection I can see. I know too many tiny, gestationally annorexic women who have huge babies and women who gain a lot who have tiny babies.
I am like Andrea. I gained nearly 60lbs during my first pregnancy. My daughter was 7lbs 5onz @ birth (textbook size according to my pediatrician) and was born 1 day past her due date. I lost over 35 lbs in the 24 hours during/after delivery. I had gestational diabetes, which was diet controlled. My weight was largely fluid retention. Weight doesn’t tell the whole story. This time around I’m over 6 months along and have only gained 14lbs. It’ll be interesting to see where this baby ends up on the scale.
My first child I was 18 I only weighed 80lbs at the time of her birth I weighed 115lbs, she was also 6 weeks early and weighed in at 4lbs 5oz. I lost my weight within days after giving birth. My second child I was 23 and weighed 85 at the time of his birth I weighed 145, he came a month before his due date and weighed 6lbs 1oz. I still looked pregnant for several months. Now pregnant with my third which will be delivered right before my 25th birthday. I began at 110lbs lost a lot due to morning sickness. I currently weigh in at 114lbs and am in my 21st week of pregnancy. Will be interesting to see if I swell up and how much this one weighs at birth. I should add that I am very short so 80lbs did not make me look annorexic I am only 4′ 10″.
I think the most important thing that this article/study fails to address is what kind of diet the weight was gained on. Was it mostly healthy food? I gained 35lbs with my 2nd pregnancy and my daughter weighed 9lbs1oz, but my husband is 6ft4in tall! I am taller than average as well. It stands to reason that our child would be bigger than average when we are bigger than average! I gained that weight eating 85% healthy and exercising by walking and some light yoga daily! I had no gestational diabetes and I had no problem getting her out! She is as healthy as a horse at five years old. She’s only ever gotten a few colds and the flu once. She never even had an ear infection! NO HEALTH PROBLEMS. Now if someone gains the weight eating mostly unhealthy food, it makes sense that the baby would be big AND have health problems.
I was 10 pounds and 1 ounce.
They first told my mom my due date was in december….I wasn’t born until Febuary.
My mom went from 98 pounds to 150 and She had 10X the normal fluid.
I don’t know if that counts for any thing and I Am NOT FAT! I weigh 145 and Is 5’5
I gained 147lbs during my 2nd pregnancy due partly to some hormone issues which are still ongoing. My baby was born a normal healthy 8lb 4oz two weeks after my due date. 5 years on she is still a normal weight and so is my first child. I am still struggling to lose weight (currently 273 lbs and 5 foot 11) but my point is obese mothers do not necessarily produce large babies.