**Core Concept**
Hepatitis in pregnancy poses significant risks to both the mother and the fetus. The severity of hepatitis during pregnancy depends on the type of virus causing the infection.

**Why the Correct Answer is Right**
Hepatitis B is the most dangerous in pregnancy due to its high risk of vertical transmission, where the virus is transmitted from the mother to the newborn during delivery. Hepatitis B virus (HBV) can be transmitted through maternal blood, vaginal secretions, or breast milk, leading to chronic infection in the newborn. The risk of transmission is higher if the mother is hepatitis B e-antigen (HBeAg) positive, indicating a high viral load.

**Why Each Wrong Option is Incorrect**
**Option A:** Hepatitis A is generally a self-limiting disease and does not pose a significant risk of vertical transmission. It is primarily spread through the fecal-oral route.
**Option B:** Hepatitis C can be transmitted vertically, but the risk is lower compared to hepatitis B. Hepatitis C virus (HCV) is primarily transmitted through blood-to-blood contact.
**Option C:** Hepatitis E is a waterborne infection that is more common in developing countries. While it can cause severe disease in pregnant women, the risk of vertical transmission is lower compared to hepatitis B.

**Clinical Pearl / High-Yield Fact**
Hepatitis B vaccination is recommended for all newborns, especially if the mother is hepatitis B surface antigen (HBsAg) positive.

**Correct Answer:** D. Hepatitis B