Cewek Genit. Dangers Chicken Pox in Pregnancy. Smallpox can strike people of all ages. Disease caused by Varicella virus can usually be cured. But if it infects pregnant women, can increase the risk of complications in mother and baby that she carried. When a pregnant woman had a history of chickenpox infection or been immunized, antibodies against this virus will be transferred to the baby through the placenta. Pregnant women will be immune and do not have to worry about complications for themselves and their babies. Incidence of chickenpox infection during pregnancy is approximately 0.05 to 0.07 percent. The amount is small because most fertile women already have immunity to varicella, but if the chicken pox acquired during the third trimester, the risk of varicella pneumonia occur is greater.