Following delivery, the nurse's assessment reveals a soft, boggy uterus located above the level of the umbilicus. The appropriate intervention is:

Place the infant on the mother's abdomen after birth. This will help the infant maintain an adequate body temperature by providing skin-to-skin contact with the mother, which reduces heat loss and promotes bonding. Skin-to-skin contact also stimulates the baby's natural feeding cues and helps initiate breastfeeding.

Choice A is not correct because turning up the temperature in the birth room may not be enough to prevent heat loss from the infant, especially if they are wet or exposed to cold surfaces. It may also make the mother uncomfortable or dehydrated.

Choice B is not correct because bathing the infant immediately after birth may increase heat loss from evaporation and conduction. It may also interfere with the baby's natural protective coating (vernix) and microbiome. Bathing should be delayed until at least 24 hours after birth.

Choice D is not correct because wrapping the infant in a warm, dry blanket may not provide the same benefits as skin-to-skin contact with the mother. It may also prevent the baby from smelling and seeing the mother's breast, which are important cues for breastfeeding initiation.

Injecting the medication into the vastus lateralis. This is because the vastus lateralis is a large muscle in the thigh that is suitable for intramuscular injections in newborns³. The vitamin K injection helps prevent vitamin K deficiency bleeding, which is a rare but serious condition that can cause bleeding in the brain or other organs¹. The American Academy of Pediatrics recommends that all newborns receive a single intramuscular dose of 0.5 to 1 mg of vitamin K within one hour of birth².

Choice A is wrong because a 21 gauge needle is too large for a newborn's muscle. A 25 or 27 gauge needle is more appropriate.

Choice B is wrong because injecting at a 45-degree angle may not reach the muscle tissue. A 90-degree angle is more appropriate.

Choice C is wrong because injecting 1cc of medication is too much for a newborn's muscle. The recommended dose of vitamin K is 0.5 to 1 mg, which is equivalent to 0.05 to 0.1 mL.