What is the primary consequence of renal agenesis in a fetus?

The primary consequence of renal agenesis in a fetus is severe pulmonary hypoplasia. When renal agenesis occurs, typically manifesting as either unilateral or bilateral absence of kidneys, it has significant implications for fetal development. In the case of bilateral renal agenesis, the absence of kidneys means that there is little to no production of urine, which contributes significantly to the amniotic fluid volume during fetal life.

Amniotic fluid plays a crucial role in lung development; it is essential for the process of fetal breathing movements that stimulate lung expansion and promote proper pulmonary development. Without adequate amniotic fluid, as would be the case with renal agenesis, the lungs do not develop properly, resulting in pulmonary hypoplasia. This condition presents a major risk for the neonate, and it is one of the leading causes of morbidity and mortality associated with congenital kidney malformations.

Other options suggest outcomes that are inconsistent with the known effects of renal agenesis. For instance, increased amniotic fluid volume, enhanced fetal growth, and normal renal function would all contradict the expected physiological changes that occur due to kidney absence in fetal development. Therefore, the relationship between renal agenesis and severe pulmonary hypoplasia is well-documented, underscoring the critical