Chloroquine has not been shown to have any harmful effects on the fetus when used for malarial prophylaxis.[20] Small amounts of chloroquine are excreted in the breast milk of lactating women. However, this drug can be safely prescribed to infants, the effects are not harmful. Studies with mice show that radioactively tagged chloroquine passed through the placenta rapidly and accumulated in the fetal eyes which remained present five months after the drug was cleared from the rest of the body.[2][21] Women who are pregnant or planning on getting pregnant are still advised against traveling to malaria-risk regions.[20]