The Health-Care Provider Recently Confirmed That a Woman Is Pregnant

The health-care provider recently confirmed that a woman is pregnant. The new mother to be is so happy because she has been trying to get pregnant for the past year. She told the nurse that her menstrual cycles have been very irregular and unpredictable, making it very hard to conceive. She "thinks her last menstrual cycle started in early September." What would be a reliable predictor of gestational age for this woman?

A) Fundal height measurements
B) Ultrasound in the first trimester
C) Levels of the human chorionic gonadotropin (hCG)
D) Using Naegele's Rule for expected date of delivery