Weight Gain In Pregnancy - Kamm McKenzie OBGYN

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Weight Gain In Pregnancy

Originally published in November 2012

I think it’s time for a little blog post about weight gain in pregnancy.  This will help many of our patients meet their ideal pregnancy weight at the time of delivery, and thus lead to the best pregnancy outcomes possible.  Before you continue reading, I want you to calculate your body mass index (BMI).  You can simply Google “BMI Calculator” or use the link below from the CDC’s website:


Why do we care about your weight gain in pregnancy?

Let’s start by discussing how the weight you gain during pregnancy impacts your child’s health and your ability to have a safe vaginal delivery.  Some of the reasons may be obvious… like, if you gain too much weight you have a higher risk of having a baby that is too large; and if you gain too little weight, you have a higher risk of having a baby that is too small.   This is important not only for the mode of delivery (bigger babies put you at higher risk for cesarean delivery), but larger babies are also at increased risk of birth trauma due to something called “shoulder dystocia” at the time of vaginal delivery.  Birth weight greater than about 9 pounds increases your baby’s risk of low blood sugar, jaundice and respiratory distress immediately after delivery.  It also increases your child’s risk of developing diabetes, hypertension, and cardiovascular disease later in life.   In addition, too much weight gain increases your risk of developing gestational diabetes and hypertension during pregnancy.

Equally important to us (as we aim to be your doctors for years), is that if you gain too much weight during pregnancy, this can be a precursor to developing obesity or to having a worsening of pre-existing obesity.  And we all know that there are many diseases associated with obesity, such as hypertension, diabetes, and heart disease.  Limiting pregnancy weight gain also allows you to get back to your pre-pregnancy weight sooner after delivery.

Where is all the weight going?

Here is a breakdown of weight gain for a non-obese woman at full term:

  • Fetus: 7-8 lb
  • Increase in blood volume: 6-8 lb
  • Increase in fluid volume (ie swelling): 2-3 lb
  • Amniotic Fluid:  2 lb
  • Breast Enlargement: 1-3lb
  • Uterine Enlargement: 2 lb
  • Placenta: 1.5lb
  • Fat Stores: 6-8lb

 So if you are gaining more than the recommended weight and are not having very severe, pathologic swelling, then you are increasing the last category on the above list– fat stores.

How much weight should you gain?

Here is where your previous calculation comes into play.

·    Underweight (BMI<18.5):  28-40lb

·    Normal Weight (BMI 18.5-24.9): 25-35lb

·    Overweight (BMI 25-29.9): 15-25lb

·    Obese (BMI≥30): 11-20lb

If you are carrying twins or triplets, you can safely add 10-15lb to the above ranges in each category. 

So what this translates into is, for underweight and normal weight women, ONE pound of weight gain weekly beginning in the second trimester.  For women overweight or obese, you should gain about ½ pound each week beginning in the second trimester.  You should not gain ANY significant amount of weight during the first trimester.

There is some evidence to suggest that women who have a BMI>35 may have more benefit than risk to gaining no weight or losing weight during their pregnancy.

Some final words of advice

Caloric intake and exercise regimens do not need to change early in pregnancy, as there should be very little or no weight gain in the first trimester.  For women who are normal weight, increasing caloric intake by 200-300 calories daily will allow you to adequately nourish your growing baby and achieve your pregnancy weight gain goals.  An example of 200-300 calorie snack would be an apple with a little bit of peanut butter.  For those of you who are overweight or obese, your caloric intake should not increase as the pregnancy progresses.

If one of your providers in the office comments on your weight or weight gain, please do not be offended.  Your weight is a vital sign that is just as important to the health of your pregnancy as your blood pressure.  Fortunately, pregnancy weight gain is something that you can control, and thereby improve the overall course of your pregnancy and the health of your baby.  

As always, our first priority is to help you reach the goal of the safest pregnancy, delivery, and post partum course possible.  

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