**Core Concept**
Peri-natal transmission of hepatitis B refers to the vertical transmission of the hepatitis B virus (HBV) from an infected mother to her newborn during the perinatal period, typically within 24 hours before, during, or after delivery. This mode of transmission is a significant public health concern, as it can lead to chronic HBV infection and its associated complications in the infant.

**Why the Correct Answer is Right**
The risk of peri-natal transmission of hepatitis B is highest when the mother is a chronic carrier of the virus and has high levels of viral replication, as indicated by high levels of HBV DNA and/or HBV e-antigen (HBeAg) in her blood. The transmission occurs through contact with the mother's blood, vaginal secretions, or other bodily fluids during delivery. The risk of transmission can be significantly reduced with the administration of hepatitis B immune globulin (HBIG) and the first dose of hepatitis B vaccine to the newborn within 12 hours of birth.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, so we'll move on to the other options.
**Option B:** This option is not correct because the risk of peri-natal transmission of hepatitis B is not highest in the second trimester of pregnancy. While maternal HBV infection during pregnancy can lead to increased viral replication and transmission risk, the peak risk period is during delivery.
**Option C:** This option is not correct because the risk of peri-natal transmission of hepatitis B is not highest in the third trimester of pregnancy. While maternal HBV infection during pregnancy can lead to increased viral replication and transmission risk, the peak risk period is during delivery.

**Clinical Pearl / High-Yield Fact**
The risk of peri-natal transmission of hepatitis B can be significantly reduced with the administration of hepatitis B immune globulin (HBIG) and the first dose of hepatitis B vaccine to the newborn within 12 hours of birth. This is a critical aspect of hepatitis B prevention and should be considered in the management of all pregnant women with known or suspected HBV infection.

**Correct Answer: D.**