Breastfeeding
You also should not take methotrexate when you’re breastfeeding. This is because methotrexate can cause serious side effects in a child who is breastfed. These side effects can include gastrointestinal problems such as nausea, vomiting, and diarrhea. They can also include blood disorders, such as low levels of blood cells. If your child develops low white blood cell levels, they’re at risk of increased infections. With low red blood cell levels, your child could develop anemia.
If you need to take methotrexate after your baby is born, talk to your doctor about other ways to feed your child.