Which BPP component is decreased by the administration of betamethasone (BMZ)?

The administration of betamethasone, a corticosteroid, leads to a decrease in the fetal respiratory movements assessed in the biophysical profile (BPP). This is primarily due to the effects of corticosteroids on the developing fetal lungs and their influence on fetal neural function and muscle tone. Betamethasone is utilized in obstetrics to accelerate fetal lung maturity in cases of anticipated preterm birth.

While it does improve lung maturation over time and is beneficial for long-term outcomes, the immediate effect may transiently diminish the observed fetal breathing movements, which are components of the BPP. In the context of the other components, movement, tone, and amniotic fluid volume are less directly impacted by betamethasone in this manner. Fetal movements may initially be unaffected, tone usually remains stable, and the amniotic fluid volume is not directly connected to the effects of corticosteroid administration. Thus, the correct answer highlights the specific impact of betamethasone on fetal breathing movements, clarifying the dynamic interplay between short-term observations and long-term health benefits.