Human Heredity 9th Edition by Michael Cummings

Exercise 3

Melissa was referred for genetic counseling 16 weeks into her pregnancy because of a history of epileptic seizures. She was on medication (valproic acid) for her seizures and had not had a seizure in the last 3 years. Her obstetrician became concerned when he learned that she was still taking this medication, against his advice, during her pregnancy. He wanted her to speak to a genetic counselor about the possible effects of this medication on the developing fetus. The counselor took a detailed family history, which indicated that Melissa was the only family member with seizures and that no other genetic conditions were apparent in the family. The counselor asked Melissa why she continued to take valproic acid during her pregnancy. Melissa stated that she was "afraid my child would have epilepsy if she didn't take her medicine." Melissa went on to say that she was teased as a child when she had her "fits," and she wanted to prevent that from happening to her children.
With this in mind, the counselor reviewed the process of fetal development and why it is best that a physician carefully evaluate all medications that a woman takes while she is pregnant. Melissa's medication has been shown to cause spina bifida, which affected almost twice as many children who were exposed to it than children who were not exposed. Using illustrations, the counselor explained that spina bifida is a defect that occurs when the neural tube fails to close completely during embryonic development. The failure to fold exposes part of the spinal area when an infant is born. Valproic acid could also cause problems in the heart and the genitals. The counselor explained that prenatal diagnosis using ultrasound, and possibly amniocentesis, could help determine whether the baby's tube had closed properly.
Postscript: Melissa elected to have an ultrasound, which showed that the baby did not have a neural tube defect. However, she was offered an amniocentesis to rule out a possible false negative result of the ultrasound. She declined the amniocentesis and delivered a healthy baby boy.
Women taking valproic acid have a 1% to 2% risk of having a child with a neural tube defect. Does the fact that Melissa had a normal child increase the risk that her next child will be affected? Why or why not?