Which of the following is a sign of labor?

Regular contractions are a primary sign of labor as they indicate the body is preparing for childbirth. These contractions occur in a predictable pattern, typically becoming stronger, longer, and closer together as labor progresses. This rhythmic tightening of the uterus helps to dilate the cervix and eventually facilitate the delivery of the baby.

Other signs, such as nausea and vomiting, constant back pain, and frequent urination, may accompany pregnancy or occur due to other conditions, but they are not definitive indicators of labor. While back pain can be a symptom experienced by pregnant individuals, it does not necessarily signal that labor is starting. Similarly, nausea and vomiting may occur at various stages of pregnancy and are not exclusive to labor. Frequent urination is also common in pregnancy but does not indicate that labor is imminent.