A: If you have regular menstrual cycles beginning every 28 days, it can be useful to date your pregnancy by the first day of your last menstrual cycle. Some women have small amounts of bleeding when implantation occurs and confuse this with another menstrual period. Other women may have bleeding from a cervical polyp (a benign vascular growth on the cervix) or from the pregnancy itself. If this bleeding is mistaken for menstruation, it can make it difficult to know how far along you are.

If you think you may be farther along in pregnancy than your menstrual calendar suggests, discuss this with your doctor. In the first trimester, the size of the uterus dramatically changes from month to month. A careful physical exam or an early ultrasound can provide excellent data for determining fetal age. A physical exam can also screen for potential causes of first trimester bleeding, such as a cervical polyp. An ultrasound can show whether any factors within the pregnancy contributed to early bleeding.

If your doctor's exam shows you to be only two months pregnant, understand that there are many factors that affect the way you look. The laxity of your abdominal muscles (stretched by previous pregnancies), the amount of fat padding your belly and even a full bladder can make you appear farther along.