At each prenatal appointment, your caregiver takes measurements of your belly to confirm that your baby is growing at a healthy rate. She measures the height of your fundus (the top of your uterus) and feels your abdomen to determine the approximate size and position of your baby. As a very general guide, your fundal height in centimeters should be about the same as the number of weeks you are pregnant.
Months 1 to 3
Despite everything that is going on inside you during the first few months of pregnancy, your belly may not appear any bigger until the second trimester, which starts with month four. Up to this point, you may not have an obvious baby belly, and may still be able to wear regular clothes.
Months 4 to 6
By the fourth month of pregnancy, you develop a more noticeable pregnancy bump, and might feel more comfortable in maternity clothes. By week 16, your fundal height may be about 14 to 18 centimeters. From the fifth month of pregnancy, you may feel like your bump is getting a little bigger by the day. Your fundal height at week 20 may be 18 to 22 centimeters. By the end of the sixth month of pregnancy, your fundal height may be 25 to 27 centimeters.
Months 7 to 9
During the seventh month of pregnancy, your baby has another growth spurt. At week 28 of pregnancy, your fundal height may be 26 to 30 centimeters. At week 32, your fundal height may be 30 to 34 centimeters. During the ninth month, you may notice your belly "drops" as your baby gets ready for birth, moving head first into the birth canal in what is known as the fetal position. At week 36, your fundal height may be 34 to 38 centimeters.
Every Belly is Different
If your friend's baby bump is a lot bigger than yours at the same stage of pregnancy, don't be concerned. The shape and size of your pregnancy belly depends largely on your own size, shape and bone structure. Muscle tone is also a significant factor: if you have very tight muscles your pregnancy belly may not be as obvious as that of a woman who has looser muscles, or one who has previously given birth. According to "What to Expect," a larger belly doesn't necessarily result in a larger baby. If you measure large or small for dates (more than 2 centimeters larger or smaller than expected at your stage of pregnancy) at your prenatal appointment, your caregiver may arrange an ultrasound. This is unlikely to be anything to worry about. If you measure large, your due date may be wrong or you may be carrying twins. Measuring small may be down to extremely tight abdominal muscles or simply genetics. If you have any concerns at all about the growth of your pregnancy belly, speak to your caregiver.