I must confess -- before I became pregnant, I was a medical wimp. A fingerprick before my wedding day and annual checkups and pap smears were the extentof my relationship with doctors, and I liked it that way. But my first prenatalexam changed all that.

I soon discovered that no matter how young or healthy, moms-to-be face avariety of prenatal tests to monitor the health of their babies and theirpregnancies. In most cases, these tests offer reassurance that everything isgoing smoothly, and many of them are meant to spot problems, such as irondeficiency or diabetes, that can be treated before complications occur.

Other tests, particularly those that are used to detect genetic problems,such as Down syndrome, cystic fibrosis or spina bifida, can present some toughchoices and worries for parents-to-be. The initial screening tests are notmeant to be conclusive. They are intended to determine if you are athigher-than-usual risk and may call for additional diagnostic tests that carrysome risk to the fetus, although the odds of a healthy baby are still high --only about 2% to 3% of all babies are born with a genetic defect.

To decide which of these tests are right for you, it's important tocarefully discuss with your doctor or midwife what these tests are supposed tomeasure, how reliable they are, the potential risks, and your options and plansif the results hold bad news, says Dr. Michael Mennuti, chairman of obstetricsat the University of Pennsylvania School of Medicine.

"If a woman and her partner say they wouldn't do anything differently ifthe test showed a problem, then the value of a diagnostic test likeamniocentesis or chorionic villi sampling (CVS) isn't there," Dr. Mennutisays. The test might be worthwhile, however, if a couple would considerterminating the pregnancy or simply wants to prepare for a child with specialneeds, he adds.

Here's a look at the most common prenatal tests you might undergo over thenext nine months. Some tests, such as urine or blood tests, might be repeatedduring your pregnancy, as will routine blood pressure screening. Others, suchas CVS and amniocentesis, may not be offered unless your age or other factorsindicate that you or your baby are at higher risk for certain conditions ordiseases.

First Trimester Tests

Here are some tests you may undergo during the first trimester of yourpregnancy:

Blood tests: During one of your initial exams, your doctor or midwifewill identify your blood type and Rh factor, measure the level of iron in yourblood, check for immunity to rubella (German measles), and test for hepatitisB, syphilis and HIV. Depending on racial, ethnic or family background, you maybe offered tests and genetic counseling to assess risks for diseases such asTay-Sachs, canavan, cystic fibrosis, thalassemia and sickle-cell anemia (ifthese weren't done at a preconception visit).