What effect does smoking have on fetal growth?

Smoking during pregnancy has a well-documented negative impact on fetal growth, primarily due to the mechanism of vasoconstriction and reduced blood supply. When a pregnant person smokes, nicotine and other harmful substances cause the blood vessels to constrict, which limits blood flow. This constriction reduces the transport of oxygen and essential nutrients to the developing fetus, ultimately impairing growth and leading to potential complications such as low birth weight or developmental delays.

The decrease in blood supply also affects placental function, further exacerbating the reduced delivery of vital nutrients and oxygen. This physiological response explains why smoking is linked to numerous adverse outcomes in pregnancy, including intrauterine growth restriction (IUGR) and increased risks for other complications.

The other choices do not accurately reflect the consequences of smoking on fetal growth. Enhanced blood flow or increased oxygen delivery directly contradicts the established understanding of how smoking affects fetal development and health.