An obstetrician sees a pregnant patient who was exposed to rubella virus in the eighteenth week of pregnancy. She does not remember getting a rubella vaccination. The best immediate course of action is to
**Core Concept**
The obstetrician needs to manage a potential rubella infection in the 18th week of pregnancy, which is a critical period for organogenesis. Rubella virus is a teratogen that can cause congenital rubella syndrome (CRS) if transmitted to the fetus.
**Why the Correct Answer is Right**
The obstetrician should administer human immunoglobulin (antibody) immediately to prevent or modify the fetal infection. This is based on the principle that high levels of IgG antibodies can neutralize the virus, thereby preventing its transmission to the fetus. The 18th week is a crucial period for organogenesis, and any intervention that can prevent or minimize fetal damage is essential.
**Why Each Wrong Option is Incorrect**
**Option A:** Administering rubella vaccine is incorrect because the vaccine is live, attenuated, and not suitable for pregnant women. The vaccine could potentially cause fetal infection.
**Option B:** Ordering a blood test to confirm the patient's immune status is incorrect because the primary concern is to prevent fetal infection, not to diagnose the patient's immune status.
**Option C:** Recommending rest and hydration is incorrect because it does not address the underlying risk of fetal infection.
**Clinical Pearl / High-Yield Fact**
Rubella vaccination is contraindicated in pregnancy due to the risk of transmitting the live, attenuated virus to the fetus. Women of childbearing age should be vaccinated before becoming pregnant to prevent CRS.
**Correct Answer:** C.