Human immunodeficiency virus (HIV) may be perinatally transmitted:

Uterine atony.

This is when the uterus does not contract enough to stop the bleeding from the placental site after delivery. It is the most common cause of postpartum hemorrhage, accounting for up to 80% of cases. Uterine atony can be caused by factors such as prolonged or augmented labor, large baby, multiple pregnancies, infection, or retained placenta.

The woman in question has some risk factors for uterine atony, such as a large baby and augmentation of labor with Pitocin.

The other choices are wrong because:

A . Retained placental fragments: This is when parts of the placenta remain attached to the uterine wall and prevent it from contracting properly. It is the second most common cause of postpartum hemorrhage.

However, there is no indication in the question that the woman had any difficulty with the delivery of the placenta or that it was incomplete

B. Unrepaired vaginal lacerations: This is when there are tears or cuts in the vagina or cervix that cause bleeding. It is a less common cause of postpartum hemorrhage.

However, there is no indication in the question that the woman had any trauma during delivery or that she was examined for lacerations

D. Puerperal infection: This is when there is an infection in the uterus or other parts of the reproductive tract after delivery.

It can cause fever, pain, and bleeding. It is a rare cause of postpartum hemorrhage.

However, there is no indication in the question that the woman had any signs or symptoms of infection, such as fever, chills, or foul-smelling discharge.

Normal ranges for blood loss after delivery are less than 500 mL for vaginal birth and less than 1000 mL for C-section.

Any amount above these thresholds can be considered postpartum hemorrhage and requires prompt evaluation and treatment.

Vernix caseosa is a cheese-like, whitish substance that fuses with the epidermis and serves as a protective coating for the newborn.

Some possible explanations for the other choices are:

• Choice B. Surfactant is a protein that lines the alveoli of the infant’s lungs and helps prevent them from collapsing.
• Choice C. Caput succedaneum is a swelling of the tissue over the presenting part of the fetal head caused by pressure during delivery.
• Choice D. Acrocyanosis is a bluish discoloration of the hands and feet due to reduced peripheral circulation.

Normal ranges for vernix caseosa are not applicable as it varies depending on the gestational age and skin maturity of the newborn. However, it is usually more abundant in preterm infants than in term or post-term infants.