Over the course of a 40-week pregnancy, you're likely to undergo more tests than ever before in your life. Some monitor your health; others, the baby's. Many are routine, while some are optional. A few are cutting-edge; most have been around for years. But one thing's for sure: The number and variety of them -- not to mention all the acronyms you're supposed to remember -- can make you feel overwhelmed.

Keep in mind that there are two types of genetic tests: A screening test assesses your risk of having a baby with a certain birth defect. A diagnostic test gives you a near-definitive answer. Here, to help, is a trimester-by-trimester guide to the tests you're likely to face, the risks involved, and what to do if there's a problem.