According to the March of Dimes, about 1 in 33 babies born each year in the U.S. has a birth defect.

That's why experts recommend that women planning to become pregnant visit their healthcare provider first. This is especially important for women with chronic health conditions, the March of Dimes says.

Cleft lip and cleft palate are birth defects of the mouth and lip. They happen in about 1 in 700 births. These problems occur early in pregnancy. The sides of the lip and the roof of the mouth don’t join together as they should. A child can have cleft lip, cleft palate, or both. Most babies born with a cleft are otherwise healthy, with no other birth problems. Down syndrome is a genetic disorder that includes a combination of birth defects. These include intellectual problems, certain facial features and, often, heart defects, visual and hearing problems, and other health problems. These problems vary greatly in how severe they are. According to the CDC, Down syndrome affects about 1 in 691 babies.

Smoking raises the risk for miscarriage or damage to developing fetal organs. Alcohol and illegal drugs can raise the risk for fetal problems, miscarriage, and lifetime disabilities.

If a woman is not immune to rubella, infection during pregnancy can cause a group of birth defects called the congenital rubella syndrome. Defects include decreased growth, intellectual problems, small head, congenital cataracts or cloudiness of the cornea, deafness, and heart defects.

Taking folic acid supplements may lower the risk for a group of conditions called neural tube defects by 50%.

This infection can be passed to humans through cat feces. It can seriously harm an unborn baby. Infection during pregnancy can cause premature delivery, low birth weight, intellectual problems, muscle movement problems, small head, small eyes and blindness, seizures, hydrocephalus, and damage to the liver and blood-forming organs.

Many prescription and over-the-counter medicines aren't safe for pregnant women to take. An expectant mother should check with her healthcare provider before taking any medicine or supplement.

Amniocentesis usually is done between the 15th and 20th week of pregnancy. Down syndrome is one of the most common genetic chromosome problems tested for. The number of conditions that can be diagnosed by amniocentesis increases every year. Amniocentesis can be used to diagnose many chromosome problems, DNA-gene problems, and enzyme and amino acid problems. In late pregnancy, amniocentesis can even help find out how mature the fetus' lungs are.

Women 35 and older have a greater risk of having a child with chromosome problems. This is especially true for trisomy 21, also known as Down syndrome.