Final answer:
The most dangerous effect on the fetus of a mother who smokes cigarettes during pregnancy is intrauterine growth restriction, which stems from reduced blood oxygen levels that are essential for fetal development.
Step-by-step explanation:
When a mother smokes, the most dangerous effect on the fetus is d. intrauterine growth restriction. This is because the presence of carbon monoxide and other harmful chemicals in cigarette smoke can lead to a reduction in blood oxygen levels, which is critical for fetal development. Smoking during pregnancy has been associated with several adverse outcomes including premature birth, low-birth-weight infants, stillbirth, and sudden infant death syndrome (SIDS).
The harmful chemicals found in cigarettes, including nicotine, act as teratogens that can cross the placenta and directly affect the developing fetus. These substances contribute to intrauterine growth restriction by reducing the availability of oxygen and nutrients that are essential for healthy fetal growth. The increased levels of carbon monoxide in the blood competitively bind with hemoglobin, reducing the blood's capacity to deliver oxygen to the fetus, which is crucial for its overall development and growth.