Which of the following is a primary indication for performing a nonstress test during pregnancy?

The correct answer is D: To assess fetal well-being in cases of suspected fetal growth restriction. Nonstress tests are used to monitor the fetal heart rate in response to fetal movement, providing information about fetal well-being. This is crucial in cases of suspected fetal growth restriction to ensure the baby is receiving adequate oxygen and nutrients. Choice A is incorrect because determining gestational age is typically done through ultrasound, not a nonstress test. Choice B is incorrect as measuring amniotic fluid volume is usually assessed through ultrasound. Choice C is incorrect as confirming labor contractions is typically done through physical examination or monitoring uterine activity, not a nonstress test.