Understanding Uterine Measurements During Pregnancy: What You Need to Know

Question
I went to my monthly prenatal visit, and I am 23 weeks pregnant with my second child.  They did the external measurements of the uterus (?) and my OB asked if I thought I was getting bigger.  I told her no, as some days you can't tell at all.  She told me that I was supposed to measure 23, but was measuring 27.  Just curious as to what that meant.  I am tall, 5'9" and bigger- 240lbs, but my daughter was about average- 7lb.10 oz and 19 inches.

Just wondering what that measurement means.  Thanks for your answer.

Answer
Measurement of the fundus of the uterus is very subjective and varies from one examiner to another. We often use a tape measure, measuring from the pubic bone to the top of the uterus. Each centimeter corresponds to a week of pregnancy. If the fundus measures 23cm, it equals 23 weeks. If it measures 27 weeks, it equals 27 weeks. As you approach 40 weeks the fundus gets  smaller and measurement is not accurate. Sometimes, the uterus appears larger if the baby is large or if you are having twins,or if you are producing lots of amniotic fluid. The best thing to do is to take a sonogram, which is much more accurate to check if there is adequate growth of the baby.