Hydramnios can be caused by which condition?

Hydramnios, or excessive amniotic fluid, can indeed be caused by gastrointestinal (GI) obstructions in the fetus. When a fetus has a GI obstruction, it is unable to effectively swallow amniotic fluid, which typically contributes to the fluid balance within the amniotic sac. In normal circumstances, the fetus swallows amniotic fluid, and this fluid is then absorbed into the GI tract and eventually excreted through urine. However, with an obstruction, this swallowing process is disrupted, leading to an accumulation of fluid, which results in hydramnios.

The other conditions mentioned do not directly result in hydramnios. Increased maternal hydration usually leads to an increase in fluid volume but does not commonly cause a pathological condition like hydramnios. Fetal heart defects can affect fluid levels, but they are more often associated with oligohydramnios (too little amniotic fluid) rather than excess fluid. Normal fetal swallowing is a physiological process that helps maintain the balance of amniotic fluid and, when functioning properly, would not cause hydramnios. Thus, gastrointestinal obstruction stands out as a significant cause of this condition.