What is the most likely fetal effect of a mother using cocaine during pregnancy?

Using cocaine during pregnancy has significant negative effects on fetal development. One of the most documented effects is lower birth weight. Cocaine use leads to vasoconstriction, which decreases blood flow and oxygen delivery to the placenta and fetus. This reduced blood flow can result in intrauterine growth restriction (IUGR), causing the fetus to grow slower than it should, ultimately leading to a lower birth weight upon delivery.

Furthermore, lower birth weight is associated with various complications, such as increased risk of neonatal intensive care unit (NICU) admission and developmental delays. The other options, such as improved fetal growth, increased muscle tone, or higher Apgar scores, do not accurately reflect the consequences of cocaine use during pregnancy. In fact, cocaine exposure is linked with adverse outcomes, not enhancements, in these areas. Thus, the correct answer highlights a significant concern in obstetric care regarding substance use during pregnancy.