Perhaps you or someone you know is having a baby. One of the most important questions (or worries) during a pregnancy is "Is the baby healthy?" or "Is the baby developing properly?" After all, the uterus in which the baby grows is essentially a "black box" relative to the outside world. How do we know that a baby is developing properly throughout the 40 weeks of gestation?

In this edition of How Stuff Works, we will examine the tests that obstetricians (the doctors who care for pregnant women during pregnancy and delivery) use to assess the development of an unborn child.

Photo courtesy of Philips Research
Ultrasound examination during pregnancy is one common form of prenatal testing