The primary risk in rubella infection during pregnancy is to the fetus. The rubella virus is able to cross the placenta, and acts as a teratogen by inducing apoptosis in fetal cells. This is termed congenital rubella syndrome. Birth defects can include deafness, ocular damage, cataracts, congenital heart defects, hepatomegaly, and developmental disability or delays. 

Infants who are exposed to rubella during weeks 0-12 of gestation have a 51% chance of developing congenital rubella syndrome. If the fetus is exposed to the virus between 12 and 26 weeks, the incidence of defects drops to 23%. Congenital rubella syndrome is rare in infants whose mothers were initially exposed to the virus after 26 weeks of gestation. Interestingly, the fetus is more likely to have birth defects if the mother contracted rubella before conception - infants whose mothers contracted the virus 0-4 weeks before conception have as much as 43% incidence of congenital rubella syndrome, due to it's long incubation period. 

Gestational hypertension is defined as a blood pressure over 140/90 mmHg or rise of more than 30 mmHg systolic or 15 mmHg diastolic over baseline. It generally develops after week 20 of pregnancy and returns to normal after delivery.

The classic triad of gestational hypertension is high blood pressure, proteinuria, and edema. New-onset headaches during a pregnancy that includes gestational hypertension may be a sign of a more severe condition, such as preeclampsia. 

Preeclampsia occurs more frequently in the last 8 weeks of pregnancy. Occurrence at an earlier gestational age is associated with increased severity and poorer outcomes for both mother and fetus.  

Ectopic pregnancy is a serious condition in which an embryo implants in tissue outside the uterus. Risk factors include pelvic inflammatory disease, tubal ligation, endometriosis, tobacco smoking, history of infertility, and the use of assisted reproductive technology.

Toxoplasmosis is a parasitic infection that is capable of crossing the placenta. It can cause birth defects such as hearing loss, learning disorders, and visual impairment. Toxoplasmosis infection is primarily a concern only in individuals who have never been exposed to the parasite before pregnancy, as most people develop immunity to infection 6-9 months after their first exposure (often through contact with cat feces in litter boxes or soil). The main routes of toxoplasmosis infection in pregnant women are exposure to cat feces, water contamination, consumption of undercooked meats, and blood transfusion. 

Of the conditions listed, the only one that is associated with Rh incompatibility between mother and fetus is hemolytic disease of the newborn (otherwise known as hemolytic disease of the fetus and newborn). In this condition, antibodies from the mother's blood attack the blood of the fetus. This is a major cause of fetal and newborn mortality and morbidity.

Hemolytic disease of the newborn occurs when an Rh negative mother is carrying an Rh positive fetus. The mother must have previously carried an Rh positive fetus and become sensitized to Rh-D antigen during miscarriage, pregnancy (due to placental rupture), or during delivery. Then, during a second pregnancy, anti-RhD antibodies from the mother's immune system can cross the placenta and attack the blood cells of the fetus, causing hemolytic anemia. 

Rh sensitization can be prevented by treatment of an Rh negative mother with Rho(D) immunoglobulin at 28 weeks, then again within 72 hours of delivery. This is a solution of IgG antibody to Rh-D, which is able to destroy any fetal red blood cells that enter the mother's bloodstream before her own immune system is able to form develop a sensitization.