## Core Concept
The transmission of HIV from an infected mother to her infant can occur during pregnancy, childbirth, or breastfeeding. The rate of transmission without any intervention is significant, but it can be substantially reduced with appropriate antiretroviral therapy and other preventive measures.

## Why the Correct Answer is Right
The correct answer, **15-45%**, reflects the wide range of mother-to-child transmission (MTCT) rates of HIV in the absence of any preventive interventions. This range accounts for various factors such as the level of maternal viremia, the mode of delivery, and whether the infant is breastfed. With the implementation of antiretroviral therapy and other preventive strategies, the transmission rate can be lowered to less than 5%.

## Why Each Wrong Option is Incorrect
- **Option A: 1-5%** - This range is incorrect because it represents the lower end of transmission rates achievable with effective interventions, not the rate without intervention.
- **Option B: 50-60%** - This option overestimates the transmission rate without intervention. While rates can vary, 50-60% is higher than the generally accepted range.
- **Option D: 70-80%** - This is significantly higher than any recognized transmission rate and does not reflect the actual risk without intervention.

## Clinical Pearl / High-Yield Fact
A crucial point to remember is that the risk of mother-to-child transmission of HIV can be dramatically reduced to less than 5% with effective antiretroviral therapy, elective cesarean delivery before the onset of labor and before the rupture of membranes, and avoidance of breastfeeding. This makes antenatal care and HIV screening crucial for preventing MTCT.

## Correct Answer: C. 15-45%.