Q&A: I don't know what to expect on my first OB visit.

The first appointment you have will most likely be devoted to confirming that you are in fact pregnant. The nurse may ask you for a urine sample to do a quick test. If it is positive, she'll then order a prenatal blood test, calculate your due date, and get you started with a prescription for prenatal vitamins (or discuss good, over-the-counter options).

How does your nurse figure out your due date? Most practices use the help of a pregnancy wheel and ovulation calendar.

Here's how you can calculate your due date: The average pregnancy is 280 days or 40 weeks. This 280-day cycle begins from the first day of your last menstrual period (LMP). If you know that date, add nine months plus seven days and that is your due date. (This is one bit of information you want to know; your due date will be indelibly etched into your brain, as this is the most common question people will ask you when they learn of your pregnancy!)

The blood your nurse collects at your first or second office visit will help determine:

• hCG levels (the confirmation pregnancy test)
• Hemoglobin (to test for anemia)
• Blood type and Rh factor
• Hepatitis B screening
• HIV testing
• Rubella titer
• Syphilis screening
• General blood chemistry