The nurse is caring for a new mother and newborn in a rooming-in unit and watches the mother put the infant in the bed, lying on her side, propped up with a pillow. The nurse should point out that this position can increase the risk of which situation?

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.

The foramen ovale closes, preventing blood exchange from right to left in the heart. This is because the foramen ovale is a fetal shunt that allows blood to bypass the lungs and flow from the right atrium to the left atrium. After birth, when the baby starts to breathe air, the lungs expand and the pulmonary resistance decreases. This causes an increase in blood flow and pressure in the left atrium, which pushes the foramen ovale closed. This prevents blood from mixing between the right and left sides of the heart and allows oxygenated blood to circulate to the body¹².

Choice A is not correct because the ductus arteriosus does not expand to allow more blood to enter the lungs. The ductus arteriosus is another fetal shunt that

connects the pulmonary artery to the aorta. It allows blood to bypass the lungs and flow from the right ventricle to the aorta. After birth, when the baby starts to breathe air, the oxygen concentration in the blood increases and causes the ductus arteriosus to constrict and close. This increases blood flow to the lungs and decreases blood flow to the aorta.

Choice C is not correct because the umbilical vein that carried oxygenated blood in utero does not become the ascending aorta entering the right atrium. The umbilical vein is a fetal vessel that carries oxygenated blood from the placenta to the fetus. It connects to either the portal vein or the ductus venosus, which then drains into the inferior vena cava. After birth, when the umbilical cord is clamped and cut, the umbilical vein collapses and becomes a fibrous cord called ligamentum teres hepatis.

Choice D is not correct because the ductus venosus does not shunt oxygenated aortic blood to the lungs. The ductus venosus is another fetal vessel that connects the umbilical vein to the inferior vena cava. It allows some of the oxygenated blood from the placenta to bypass the liver and enter directly into the systemic circulation. After birth, when the umbilical cord is clamped and cut, the ductus venosus closes and becomes a fibrous cord called ligamentum venosum.