A pregnant woman's diet may not meet her need for folates. A good source of this nutrient is:

Choice A reason: Variability refers to the fluctuations in the FHR that are irregular in amplitude and frequency. It reflects the balance between the sympathetic and parasympathetic nervous systems of the fetus. A normal variability is between 6 and 10 beats/min, which indicates a healthy and well-oxygenated fetus.

Choice B reason: Late decelerations are decreases in the FHR that begin after the peak of a contraction and return to the baseline after the contraction ends. They are caused by uteroplacental insufficiency, which means that the placenta is not delivering enough oxygen and nutrients to the fetus. Mild late decelerations are not reassuring and may indicate fetal hypoxia or acidosis².

Choice C reason: FHR should change as a result of fetal activity, such as movement, sleep, or stimulation. A change in the FHR indicates a responsive and well-oxygenated fetus. A lack of change in the FHR may indicate fetal distress or compromise.

Choice D reason: The average baseline rate is the mean FHR rounded to increments of 5 beats/min during a 10-minute window, excluding periods of marked variability, accelerations, or decelerations. A normal baseline rate is between 110 and 160 beats/min. A baseline rate between 100 and 140 beats/min is not necessarily abnormal, but it may indicate fetal bradycardia (slow heart rate) or tachycardia (fast heart rate), depending on the gestational age and other factors.

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: Intrauterine growth restriction is not the most dangerous effect, as it is not life-threatening and can be managed by proper prenatal care and monitoring. Smoking can reduce the blood flow and oxygen delivery to the placenta and the fetus, which can impair the fetal growth and development. Smoking can also cause low birth weight, which can increase the risk of complications and infections in the newborn².

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: Extensive central nervous system damage is the most dangerous effect, as it is irreversible and can affect the child's health and development for life. Smoking can cause hypoxia (low oxygen) and ischemia (low blood flow) in the fetal brain, which can damage the neurons and impair the brain function. Smoking can also alter the brain structure and chemistry, which can affect the cognitive, behavioral, and emotional outcomes of the child. Smoking can increase the risk of learning disabilities, attention deficit hyperactivity disorder (ADHD), and mental disorders in the child.