Your OB/GYN can:

• Discuss what precautions you should take if you have high blood pressure or diabetes, the latter of which can put your baby at up to triple the risk of birth defects. Other conditions you'll need to monitor include heart disease, asthma, lupus, and epilepsy.
  
  
• Let you know if any prescription drugs you're taking may harm your baby, such as antibiotics (tetracycline), blood thinners, antiseizure drugs (Dilantin), acne-preventives (Accutane), and blood-pressure reducers (ACE inhibitors). Other drugs that may hurt the baby include aspirin, antihistamines, and diet drugs.
  
  
• Determine if your child is at risk for seizures, mental disabilities, or birth defects such as cystic fibrosis, muscular dystrophy, hemophilia, sickle cell anemia, or Tay-Sachs disease.
  
  
• Give you a prescription for prenatal vitamins that contain 400 micrograms of folic acid, a supplement essential to helping prevent the birth defect spina bifida. If taken within four weeks of conception, the vitamin thwarts this defect, occurring in one of 1,000 births, in which the spinal column does not properly close.
  
  
• Provide you, if needed, with a measles, mumps, tetanus, polio, rubella, or hepatitis B vaccine at least three months before you get pregnant, to protect the baby.
  
  
• Give you guidelines on how to reduce your weight if you're more than 20 pounds overweight, which may put you and the baby at greater risk.
  
  
• Offer nutrition and exercise guidelines.