Time Frame | Possible Fetal Effects* | Status of the Fetus |
---|---|---|
Within 20 days after fertilization | An all-or-nothing effect (death of the fetus or no effect at all) | The fetus is highly resistant to birth defects. |
3‒8 weeks after fertilization | Possibly no effect A miscarriage Miscarriage A miscarriage is a pregnancy loss before 20 weeks of pregnancy. Miscarriages are very common, especially early in pregnancy. Most of the time, the cause of a miscarriage is unknown, but it may... read more An obvious birth defect Overview of Birth Defects A permanent but subtle defect that is noticed only later in life An increased risk of childhood cancer Overview of Childhood Cancer In the United States, the overall incidence of cancer in children and adolescents has increased over time. From 1975 to 2022, rates increased by approximately 0.8 per 100,000 each year. However... read more , as may result from giving the mother radioactive iodine (to treat thyroid cancer) or using a radioactive substance in an imaging test (such as radionuclide scanning Radionuclide Scanning Radionuclide scanning is a type of medical imaging that produces images by detecting radiation after a radioactive material is administered. During a radionuclide scan, a small amount of a radionuclide... read more ) | The fetus's organs are developing, making the fetus particularly vulnerable to birth defects. |
Second and third trimesters | Changes in the growth and function of normally formed organs and tissue Unlikely to cause obvious birth defects Unknown long-term effects | Organ development is complete. |
* Only certain medications are likely to have harmful effects. |