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Gaining Weight “Too Fast” in your 2nd trimester? That’s Probably Normal.

About that second trimester weight gain…

At my 24-week appointment when I was pregnant with my first, I finally felt pretty good, happily ensconced in the “best” trimester. My nausea had faded, my energy was back, and I was working out again after a two-month hiatus.

Then came the weigh-in.

According to my doctor, I had gained “too much weight” in the last month. I was shocked. Up until then, my trajectory predicted a healthy 30 pound gain.  But now, she explained, I was projected to gain 40 lbs. Five pounds over the recommended 25-35 lbs.

The lecture began – “Eat only half the sandwich. Don’t eat for two.”

Okay, I’ll confess, at that point, I stopped listening, and started wondering: Does this even make sense?

Is gaining weight in pregnancy really supposed to be constant? The same amount week after week, month after month – as she and her nifty weight gain chart seem to assume?

Should weight gain be consistent throughout pregnancy?

The answer? Of course not.

The good folks at the Institutes of Medicine (IOM) who came up the current weight gain guidelines for pregnant women agree:

“The pattern of Gestational Weight Gain is most commonly described as sigmoidal, with mean weight gains higher in the second than the third trimester across BMI categories, except for obese women”

IOM 2009 report on pregnancy weight gain, pg. 101.

Unfortunately, the IOM explained this in such obscure researcher-speak that the message may have gotten lost.

In plain English: pregnant women usually gain more weight in their second trimesters than in their third.

Yup, that’s right.  A higher second trimester weight gain is normal. You are not doing something wrong. You are not destined to put on too much weight by the end of pregnancy.


A higher second trimester weight gain is normal. You are not doing something wrong.


Go ahead and eat your whole darn sandwich.

Why do women gain the most weight in their second trimester?

For one, you add a ton of water weight in the second trimester. Did you notice that around month 5 you are suddenly constantly, unquenchable thirst, despite downing what feels like a gallon of water every day? It’s not all in your head, it’s biology.

In your second trimester, your belly swells up with a couple extra pounds of amniotic fluid and a rapidly growing uterus. Welcome to the world, bump! At the same time, your blood volume soars by nearly 50%.

Once you’re past your second trimester, weight gain usually slows down. (Unless you are lucky enough to have full body swelling, which can add an additional seven pounds of water weight in your arms and legs. Isn’t pregnancy fun!)


In your second trimester, your belly swells up with a couple extra pounds of amniotic fluid and a rapidly growing uterus. Welcome to the world, bump!


I do not mean to dismiss the real risks of gaining too much in pregnancy, especially for women who start out pregnancy with a high BMI. Women who go over the IOM guidelines (see below) are at higher risk for C-sections, for large babies with a risk of getting stuck on their way out (ouch!), and for difficulty losing weight postpartum.

IOM Guidelines for weight gain in pregnancy; second trimester weight gain
IOM Guidelines for weight gain in pregnancy

Very rapid weight gain (more than 2 lbs in a week) can signal preeclampsia, a serious and dangerous condition involving high blood pressure and protein in your urine. If you notice you a sudden jump in weight in a short period of time, definitely talk to your doctor.

When it comes to second trimester weight gain, keep this in mind:

Weight gain in one week of pregnancy does not predict weight gain in the next week.

So, for the majority of us without specific risk factors, let’s put this “trajectory” idea to rest?

Weight gain in pregnancy is not a steady climb. It’s not meant to be. And gaining a lot during your second trimester weight gain—that’s perfectly normal.

Enjoy your sandwich.

Looking for a perfect week-by-week nutrition guide? Check out our Baby Building Blocks Newsletter! It’s the what, when, why and how of prenatal nutrition.

This article was originally posted on


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About Amy

Amy Kiefer is a researcher by training, and earned her Ph.D. from the University of Michigan. She currently lives in the Bay Area with her husband and three children where she writes about fertility, pregnancy, and breastfeeding. Check out her blog,, for more great evidence-based pregnancy and parenting info.


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