Question

A 28-year-old G1 presents for prenatal care. Her periods have been irregular and she does not recall when the last one occurred. She is healthy and denies any medical problems. The uterus is 10 weeks in size and there are no adnexal masses. At this point in time, what is the best way to date the pregnancy?

A. Qualitative serum hCG
B. Quantitative serum hCG
C. Ultrasound measurement, gestational sac
D. Ultrasound measurement, crown-rump length
E. Uterine size on pelvic exam

Answer 1

For a pregnant woman with irregular periods, the best method to date the pregnancy is through an ultrasound measurement of the crown-rump length (CRL), which is the most accurate way to determine gestational age in early pregnancy.

Step-by-step explanation:

Best Method for Dating Pregnancy

A 28-year-old woman who is pregnant for the first time presents with irregular periods and an uncertain last menstrual period. Considering her situation, the best method for dating the pregnancy would be through an ultrasound measurement, specifically assessing the crown-rump length (CRL). The crown-rump length is the measurement of the length of human embryos and fetuses from the top of the head (crown) to the bottom of the buttocks (rump). This method has been found to be the most accurate in determining gestational age, especially when the last menstrual period is unknown or irregular.

Other methods such as qualitative or quantitative serum hCG tests are helpful for confirming pregnancy but are not as precise as an ultrasound for dating purposes. Additionally, the size of the uterus on pelvic exam can vary significantly between individuals and thus is not a reliable indicator of gestational age. In early pregnancy, CRL is used until the fetus's measurements are large enough to allow for assessment of the biparietal diameter and other fetal biometry.