**Core Concept:** Oligohydramnios is a medical condition characterized by reduced amniotic fluid volume, which can lead to impaired fetal development and potential complications during delivery. Amniotic fluid plays a crucial role in cushioning the fetus, facilitating lung development, and providing a sterile environment for the fetus.

**Why the Correct Answer is Right:** Oligohydramnios is primarily related to conditions that disrupt the production, absorption, or maintenance of amniotic fluid. In this case, option D (Intrauterine growth restriction) is the correct answer. Intrauterine growth restriction (IUGR) is a condition where the fetus fails to grow at a normal rate despite adequate blood flow to the placenta. The reduced fetal growth can lead to decreased amniotic fluid volume, as the fetus takes up less space and requires less amniotic fluid.

**Why Each Wrong Option is Incorrect:**

A. Amniotic fluid volume does not directly correlate with gestational age, hence being premature does not directly cause oligohydramnios.
B. This option is incorrect because the primary cause of oligohydramnios is not a lack of maternal steroid production, but rather impaired fetal growth and development.
C. While premature rupture of membranes can lead to oligohydramnios, it is not the primary cause of this condition.

**Clinical Pearl:** Monitoring amniotic fluid index (AFI) and amniotic fluid volume is essential during pregnancy to identify and manage potential complications like oligohydramnios and its associated risks like preterm premature rupture of membranes (PPROM), preterm labor, and intrauterine growth restriction (IUGR). Regular prenatal check-ups help ensure proper fetal growth and development, leading to a healthier pregnancy outcome.