Which additional sign suggests that a pregnant client may have mild preeclampsia?

The presence of trace amounts of protein in urine is an important indicator of mild preeclampsia. Preeclampsia is characterized by new-onset hypertension and often includes proteinuria, which is the presence of excess protein in the urine. The detection of even small amounts of protein can signal the beginning of trouble in the body's response to pregnancy and can suggest that the woman's condition needs to be monitored closely.

The other signs mentioned, such as severe headaches, swelling in the hands, and weight loss during pregnancy, can either indicate different concerns or do not have the same direct correlation with mild preeclampsia. Severe headaches could suggest other complications, swelling in the hands could be normal in some cases, and weight loss is not typical or expected during a healthy pregnancy. Hence, observing protein in the urine, even in trace amounts, directly supports concerns related to preeclampsia and warrants further evaluation.