It is possible to become pregnant during the 3-month period of cortisone's effects. However, there is limited research on the safety of cortisone injections during pregnancy or just before conception. Some studies suggest that there may be an increased risk of birth defects, especially if the injection is given near the beginning of the pregnancy. The risk may vary depending on the type of cortisone used. To minimize risks, it is recommended to wait before planning a pregnancy if possible. Starting prenatal vitamins 3 months before conception is also advised. If you are interested, you can consult at a pharmacy for the right type of vitamins for your situation.