Pregnancy and weight gain. What is it for?

Posted on March 17, 2011

I am a mom.  I gained weight with pregnancy.  How much is “me” and how much is my new baby?  When I gave birth to my first child, I couldn’t stop thinking about it.  As much as I did not want to give birth to a 30 pound baby (OUCH), somewhere lurking in my mind, I thought, “of course this baby must weigh 30 pounds!”  So in my little dreamworld, I thought I would painlessly deliver my 30 pound baby and leave the hospital zipped up in my favorite pre-pregnancy jeans, back to my normal little self.

ha ha.

Most babies don’t weigh 20-40 p0unds, and no one tells you the dirty little secret that those maternity clothes should be called maternity and mother-with-newborn-can’t-wear-normal-clothes-yet clothes.  Most of us take months to get smaller.  When we gain weight with pregnancy where is it?  Is it water weight? Fat? Blood volume?  Why do some lose it so quickly and others don’t?

When you gain weight with pregnancy, some of it is clearly the weight of the baby.  I have researched many sources, and the consensus of a typical pregnancy is:

Baby – 7½ pounds
Enlargement of uterus – 2 pounds
Placenta – 1½ pounds
Amniotic fluid – 2 pounds
Breast enlargement – 2 pounds
Extra blood and fluid volume – 8 pounds
Extra fat stores – 7 pounds
Total – 30 pounds

If you are gaining more, then the question comes, which of these is it?  Babies, placentas, amniotic fluid, and breasts likely aren’t going to be a big contributor.  So when you see women who really balloon up, the likely cause is extra fluid or extra fat.  The women who lose a ton of weight in the first week likely are those who carried a lot of extra fluid, and lose it right after birth.  The others… well those are women who likely have extra fat.  This is much harder to lose, and a common reason why I see women plateau at a higher weight than their prepregnancy weight.

So look at the blogs on the guidelines of how much weight to gain during pregnancy.  For a normal BMI woman with a healthy pregnancy,  you should gain 25-35 pounds.