Final answer:
The correct answer to the question is 'a) Vertical'. Vertical transmission refers to the pathogen travel from an infected mother to her child during pregnancy or delivery, and this includes diseases like HIV, syphilis, and rubella.
Step-by-step explanation:
The spread of disease mentioned in the question, which occurs across the placenta or from mother to newborn, is known as vertical transmission.
This form of transmission is directly from mother to child and can occur during pregnancy, childbirth, or breastfeeding.
Significant diseases that utilize this path of transmission include HIV, syphilis, and rubella.
Unlike sexual transmission, which involves the direct contact of mucous membranes during sexual activities, vertical transmission is specifically between mother and child.
This method accounts for most HIV infections in children and can also occur with other pathogens, such as those leading to congenital infections like herpes.