Pregnancy is affected by flea bites.  Some bacteria carried by fleas can be passed to the baby directly.  Babies can also be born with certain defects caused by bacteria carried by fleas such as the Bartonella bacteria. Using certain solutions against fleas such as flea sprays may not be recommended during pregnancy. Applying certain flea sprays on your pets is not recommended when pregnant. These sprays can be inhaled and their chemicals can be transmitted to the baby at all stages of pregnancy.