Correct Answer: A

Rationale: The correct answer is A: Rhesus D incompatibility. Icterus gravis (severe jaundice) and hydrops fetalis (abnormal accumulation of fluid) are both conditions commonly associated with Rhesus D incompatibility between a mother and her fetus. This occurs when the mother is Rh-negative and the fetus is Rh-positive, leading to maternal antibodies attacking the fetal red blood cells, resulting in severe hemolytic anemia and subsequent complications. Explanation for why other choices are incorrect: B: ABO incompatibility typically leads to less severe jaundice and hemolytic disease compared to Rhesus D incompatibility. C: Physiological jaundice is a common and benign condition in newborns caused by the immaturity of the liver, not by blood type incompatibility. D: Instant perinatal death is not specifically associated with these conditions, but rather with other serious complications during childbirth.

Correct Answer: B

Rationale: The correct answer is B: CT scan without contrast. A CT scan is the most useful imaging study in assessing for findings consistent with a history of abuse in this patient. CT scan is preferred for acute trauma to the head as it provides detailed images of the brain, skull, and facial bones. It can detect acute hemorrhages, fractures, or other signs of trauma. In this case, the patient's presentation with periorbital ecchymosis and facial swelling raises suspicion for traumatic injury, which can be assessed effectively with a CT scan. Radiographs (choice A) are not as sensitive as CT scans in detecting subtle fractures or soft tissue injuries in the head and face. MRI (choice C) is not typically used in acute trauma assessment and may not provide timely information needed in this case. PET scan (choice D) is not indicated for evaluating traumatic head injuries and is more commonly used for assessing metabolic and functional activity in the body.

Correct Answer: A

Rationale: The engaging diameter in a face presentation is the sub-mento vertical diameter. This is the correct answer because it represents the distance from the tip of the chin (mentum) to the highest point on the skull (vertex), which is the most critical diameter for the face to descend through the pelvis during childbirth. Choice B (Sub-mento bregmatic diameter) is incorrect because it represents the distance from the tip of the chin to the anterior fontanelle, not the highest point on the skull. Choice C (Mento vertical diameter) is incorrect because it refers to the distance from the chin to the base of the skull, not the highest point on the skull. Choice D (Sub-occipito bregmatic diameter) is incorrect because it represents the distance from the base of the skull to the anterior fontanelle, not involving the chin.

Correct Answer: B

Rationale: The correct answer is B: Hyperbaric oxygen. Hyperbaric oxygen therapy is the most effective treatment for pneumatosis as it helps to reduce gas cysts by increasing oxygen levels in the tissues. This promotes healing and resolution of the condition. A: Several days of oxygen by face mask - Regular oxygen therapy is not as effective as hyperbaric oxygen in treating pneumatosis. C: Surgical resection - Surgical resection is not typically the first-line treatment for pneumatosis and is usually reserved for severe cases or complications. D: Treatment of underlying disease - While treating the underlying disease is important, it may not directly address the gas cysts in the gastrointestinal tract. Hyperbaric oxygen therapy targets the gas cysts specifically.

Correct Answer: D

Rationale: The correct answer is D because the main aims of an exchange transfusion procedure are to control haemolysis (process of breaking down red blood cells) and restore hemoglobin levels. This procedure involves removing the baby's blood and replacing it with donor blood to prevent complications from severe jaundice or other conditions. Choice A is incorrect because exchange transfusion does not necessarily cure haemolysis, but it helps control it. Choice B is incorrect as the procedure focuses on managing specific issues rather than removing all toxic materials. Choice C is incorrect because it does not directly address the primary goals of an exchange transfusion.