Which factors contribute to maintaining a patent ductus arteriosus during fetal life? 1. Large amounts of fetal hemoglobin 2. Low PaO2 3. Presence of LDH 4. Presence of prostaglandins
a. 1, 2, and 3
b. 2 and 4
c. 3 only
d. 1, 2, 3, and 4
ANS: B
The relatively low PO2 and various prostaglandins in fetal blood cause the ductus arteriosus, a muscular vessel attached to the trunk of the pulmonary artery and the aorta, to dilate and the pulmonary arteries to constrict.
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