• Spermicides
  Spermicides are agents which impair the ability of sperm to fertilize an egg. This means that spermicides never even get to the developing pregnancy, since their job is to prevent pregnancy to begin with. However, studies from the 1970's and 1980's suggested that spermicides did cause some birth defects. Several subsequent studies, however, show no association with the use of spermicides and an increased chance for birth defects. 
  

• Acetaminophen
  Acetaminophen is the active ingredient in some pain relievers. Thousands of women have taken acetaminophen containing pain relievers during pregnancy and there has been no association with an increased chance for birth defects, when used at or below the recommended dosage.
  

• Prenatal vitamins
  Prenatal vitamins are prescribed when a woman becomes pregnant to supplement her diet to meet the growing nutritional needs of pregnancy. The amount of vitamins contained in a prenatal vitamin are calculated to specifically address some of the biological changes that happen when a woman is pregnant, such as the increased blood volume. When used at the recommended dosage, prenatal vitamins do not increase the risk for birth defects.

It is important to know that taking extra vitamins, minerals, or herbal supplements, in addition to a prenatal vitamin during pregnancy, can be dangerous to the developing fetus. This is because the extra vitamins, minerals, and/or herbal supplements can add up to a toxic effect for the pregnancy, and may be teratogenic. Be sure to check with your physician before taking any over-the-counter vitamins, minerals, or herbal supplements while pregnant.

• Microwave ovens
  There are two types of radiation: ionizing and non-ionizing radiation. X-rays are an example of ionizing radiation, while ultraviolet rays (sunlight) and microwaves are examples of non-ionizing radiation. Non-ionizing radiation is not teratogenic. Just as the mother being outside in the sunlight during pregnancy does not interfere with the development of the fetus, microwaving food while pregnant is not known to increase the risk for birth defects or health problems.