 The fetus is at greatest risk during the first 14th to 60th day of the pregnancy when the major organs are being formed.However, depending on the type of toxicant and amount of exposure, a fetus can be exposed toxicant at any time during pregnancy.For example, exposure to a particular toxicant at one time in the pregnancy may result in organ damage and at another time in the pregnancy could cause death of the fetus and miscarriage.