My husband & I are traveling to Africa and I have been prescribed antimalarial-atovaquone proquanil. We are ready to have a baby. What are the risks?

Not if pregnant. The only preventative malaria medicine for this area--in possible case of pregnancy--is use of Mefloquine but not atovaquone/proguanil. You should let your doctor know about possibility of pregnancy and he can switch your prescription. Mefloquine has side effects you should learn about but is safer for a potential fetus.
Category C. This medication falls into category c of pregnancy risk.This group of meds include those where animal studies show an adverse effect on the fetus but not enough data on human exposures is available to know more.In general the first 12 wks is the most worrisome period for fetal development. I would put off trying until you were off the med & it was completely out of your system.