This is ACOG Practice Guideline No. 151. The full text is long and detailed, and because too many people are concerned and misunderstandings abound, its relevant recommendations and summaries are briefly described below. The following recommendations and summaries are based on good, consistent scientific evidence (Level A evidence) In pregnant women with a serologic diagnosis of acute microvirus B19 infection, the development of fetal anemia should be monitored by serial ultrasound. Peak systolic blood flow in the middle cerebral artery of the fetus should be monitored with Doppler ultrasound, as this test has become an accurate predictor of fetal anemia. Varicella virus infection can cause severe maternal lesions and oral acyclovir during pregnancy appears to be safe and taken at the time of presentation of the lesion. Although the effectiveness of intravenous acyclovir has not been formalized in randomized controlled studies, it may reduce maternal morbidity and mortality associated with varicella pneumonia. Pregnant women without herpes varicella virus immunity who are exposed to a patient with an active primary infection with varicella should receive varicella immunoglobulin therapy as soon as possible, preferably within 96 hours of exposure, thereby preventing or attenuating the disease manifestations of varicella virus infection. Pregnant women with acute Toxoplasma gondii infection should be treated with spiramycin to reduce transplacental transmission of the parasite. Fetuses infected with Toxoplasma gondii should be treated with etanercept, sulfadiazine, and folic acid, a regimen that is more effective than spiramycin for eliminating placental and fetal parasitic infections and reduces the severity of disease in affected fetuses. The following recommendations and summary are based on limited or inconsistent scientific evidence (level B evidence) Routine serologic screening for cytomegalovirus is not recommended for pregnant women. Routine serologic screening for microvirus B19 is not recommended for pregnant women. Routine serologic screening for Toxoplasma gondii is not recommended for pregnant women. Pregnant women exposed to B19 should be screened serologically as soon as possible to determine if monitoring of serologic indicators is needed. If fetal edema or severe fetal anemia develops after infection with B19, a fetal blood sample should be obtained to check the erythrocyte count in preparation for fetal blood transfusion. Despite the risks associated with the procedure, intrauterine transfusion should be considered in cases of severe fetal anemia. The following recommendations are based on consensus and expert opinion (level C evidence) In early pregnancy, the immune status of the pregnant woman for varicella should be clarified by a history of previous infection or varicella vaccination. If the pregnant woman denies a history of infection or vaccination, this should be documented and varicella IgG serostatus should be checked.