A woman is using the basal body temperature (BBT) method of contraception. She calls the clinic and tells the nurse. "My period is due in a few days, and my temperature has not gone up." The nurse's most appropriate response is

A. "This probably means that you're pregnant.": A rise in basal body temperature occurs after ovulation due to progesterone release, not pregnancy itself. If temperature has not increased, ovulation likely did not occur, making pregnancy improbable in this cycle. B. "You probably didn't ovulate during this cycle.": The BBT method tracks ovulation by detecting a 0.3–0.6°C (0.5–1.0°F) temperature rise after ovulation. If no rise is noted before menstruation, it suggests an anovulatory cycle in which ovulation did not take place. C. "Have you been sick this month?": Illness can temporarily affect BBT readings, but the absence of any rise throughout the cycle more strongly indicates lack of ovulation. Asking about illness may be useful but does not directly explain a consistently low temperature pattern. D. "Don't worry: it's probably nothing.": Dismissing the concern is inappropriate and nontherapeutic. The nurse should provide education on possible anovulatory cycles and encourage continued charting or further evaluation if irregular patterns persist.