An infant's axillary temperature is 35.9C (96.6F). The priority nursing action is to:

Choice A reason:

Basal metabolic rate reduction. This is incorrect because a newborn under a radiant heat warmer will have an increased basal metabolic rate, not a reduced one. The basal metabolic rate is the amount of energy the body uses at rest, and it is influenced by temperature. A warmer environment will stimulate the newborn's metabolism and increase the energy expenditure. • Choice B reason:

Brown fat production. This is incorrect because a newborn under a radiant heat warmer will have less need for brown fat production, not more. Brown fat is a type of fat tissue that generates heat by burning calories. It is found in newborns and helps them maintain their body temperature in cold environments. A warmer environment will reduce the need for brown fat activation. • Choice C reason:

Shivering. This is incorrect because a newborn under a radiant heat warmer will not shiver, but shivering is not the main mechanism of heat production in newborns. Shivering is an involuntary contraction of muscles that generates heat by increasing metabolism. Newborns have limited ability to shiver because of their immature nervous system and low muscle mass. They rely more on brown fat and increased metabolic rate to produce heat. • Choice D reason:

Cold stress. This is correct because a newborn under a radiant heat warmer will prevent cold stress, which is a condition where the newborn's body temperature drops below normal and causes adverse effects. Cold stress can impair oxygen delivery, increase acidosis, decrease blood glucose, and increase the risk of infection and bleeding. A radiant heat warmer provides a neutral thermal environment for the newborn and prevents heat loss by radiation.

: 1 : 2 : 3 : 4.

The correct answer is choice B. Prolactin.

Choice A reason:

Estrogen. Estrogen is a hormone that plays a role in the development of the mammary glands and the ductal system during pregnancy. However, estrogen does not directly produce milk.

In fact, high levels of estrogen during pregnancy inhibit milk secretion by blocking prolactin. Therefore, estrogen is not the hormone necessary for milk production. • Choice B reason:

Prolactin. Prolactin is the hormone responsible for the production of breast milk. Prolactin is secreted by the pituitary gland in response to suckling or nipple stimulation. Prolactin levels rise during pregnancy and peak after delivery, when the sudden drop in estrogen and progesterone allows prolactin to take over and initiate lactation. Therefore, prolactin is the hormone necessary for milk production. • Choice C reason:

Progesterone. Progesterone is a hormone that also contributes to the development of the mammary glands and the alveoli during pregnancy. However, like estrogen, progesterone does not directly produce milk. Progesterone also inhibits milk secretion by blocking prolactin during pregnancy. Therefore, progesterone is not the hormone necessary for milk production. •

Choice D reason:

Lactogen. Lactogen is not a hormone, but a general term for any substance that stimulates lactation. There are different types of lactogens, such as human placental lactogen (hPL), which is produced by the placenta during pregnancy and has some lactogenic effects on the mammary glands. However, hPL is not the main hormone responsible for milk production. That role belongs to prolactin. Therefore, lactogen is not the hormone necessary for milk production.