What is the most dangerous effect on the fetus of a mother who smokes cigarettes while pregnant?

Choice A reason: Genetic changes and anomalies are not the most dangerous effect, as they are rare and not directly caused by smoking. Smoking can increase the risk of some birth defects, such as cleft lip and cleft palate, but these are not genetic changes and can be corrected by surgery. Smoking can also cause chromosomal abnormalities in the eggs, but these usually result in miscarriage or stillbirth, not live births.

Choice B reason:Maternal smoking is a significant risk factor for intrauterine growth restriction (IUGR). Nicotine and carbon monoxide from cigarettes reduce oxygen supply to the fetus, leading to lower birth weights and smaller body lengths.

Choice C reason: Fetal addiction to the substance inhaled is not the most dangerous effect, as it is not permanent and can be treated by medication and supportive care. Smoking can expose the fetus to nicotine, carbon monoxide, and other harmful chemicals, which can cross the placenta and affect the fetal brain and nervous system. Smoking can also cause withdrawal symptoms in the newborn, such as irritability, tremors, and difficulty feeding.

Choice D reason:Although prenatal exposure to smoking can affect neurodevelopment and is associated with behavioral issues, extensive central nervous system damage is not the most immediate or dangerous effect. The most critical concern remains intrauterine growth restriction.

Choice A reason: The NST has no known contraindications, as it is a non-invasive and safe test that does not stimulate uterine contractions or cause fetal distress. It is the most widely used method of antepartum fetal surveillance.

Choice B reason: The NST is not slightly more expensive than the CST, as it requires less time and equipment. The NST usually takes 20 to 40 minutes, while the CST may take up to 2 hours. The NST only needs a fetal monitor, while the CST also needs an intravenous line and oxytocin infusion.

Choice C reason: The NST does not have fewer false-positive results than the CST, as it has a higher rate of nonreactive results that may indicate fetal compromise when there is none. A nonreactive NST is one that does not show at least two accelerations of the fetal heart rate of 15 beats per minute or more lasting 15 seconds or more in a 20-minute period.

Choice D reason: The NST is not more sensitive in detecting fetal compromise than the CST, as it has a lower predictive value for fetal well-being. A reactive NST is one that shows at least two accelerations of the fetal heart rate of 15 beats per minute or more lasting 15 seconds or more in a 20-minute period. However, a reactive NST does not rule out the possibility of fetal hypoxia or acidosis.