Which of the following can indicate the need for a fetal ultrasound?

Decreased fetal movement is a significant indicator that may prompt the need for a fetal ultrasound. Fetal movement is an essential sign of the baby’s well-being, and any noticeable decrease can warrant further investigation. An ultrasound can help assess the baby's heart rate, growth, and overall condition, providing critical information that can guide healthcare providers in ensuring the fetus's health.

Increased fundal height, while it may prompt further evaluation, does not directly indicate fetal well-being. It may suggest issues such as multiple pregnancies or excess amniotic fluid but does not specifically signal the need for an ultrasound.

Low levels of maternal weight gain, on the other hand, can be important for evaluating the pregnancy's progress, but they do not directly correlate with fetal health in the same immediate way as decreased fetal movement does.

Severe headache can be concerning during pregnancy and may indicate conditions such as preeclampsia, but it is not a direct indicator for ultrasound specific to assessing fetal condition. While it requires attention and monitoring, it typically leads to other forms of evaluation rather than immediate ultrasound for fetal assessment.

Since decreased fetal movement provides a direct rationale for performing an ultrasound to check on the fetus's health and safety, it is the most appropriate choice in this context