As soon as a woman discovers she's pregnant, she embarks on a life-altering journey. As the baby grows and changes inside of her, she goes through a series of changes, too. If armed with the right tools and information, she can help ensure a smooth pregnancy and the birth of a healthy baby. Here, a look at pregnancy by the numbers.

  • 6 million: Approximate number of pregnancies in the U.S. each year, according to the American Pregnancy Association.

  • 4.1 million: Approximate number of live births in the U.S. each year.

  • 3: Approximate percentage of pregnant women who give birth to twins.

  • 467,000: Approximate number of American babies born prematurely each year.

  • 25.2: Average age of first-time mothers in 2006, according to the U.S. Census.

  • 2 million: Estimated number of married couples who deal with infertility each year.

  • 14: Average length (in hours) of labor when giving birth to a first baby.

  • 7.5: Average weight (in pounds) of a full-term newborn.

  • 74: Percentage of new mothers who breastfeed their babies.

  • 400: The recommended daily amount (in micrograms) of folic acid for women planning to become pregnant, according to the U.S. Centers for Disease and Control.