Is erbitux safe for women who are pregnant or breastfeeding?

No. Erbitux is a class c medication for pregnancy, meaning it is not considered safe (generally because animal studies have shown adverse fetal effects). It is also considered unsafe for lactation because data suggests high risk of significant adverse effects. Obviously, it is only used in very serious illnesses, but pregnancy should then be avoided and formula feeding would likewise be recommended.
No. Erbitux is an antagonist of epidermal growth factor receptors(egfr) which blocks growth of skin cells. Therefore, its' use for pregnant and breast feeding mothers is not recommended as it is transmitted in breast milk and across the placenta into amniotic fluid to the developing fetus.