Pregnancy dating acog

The American College of Obstetricians and Gynecologists (ACOG) have guidelines for pregnancy dating. According to ACOG, a provider's initial estimate of gestational age should be based on a first-trimester ultrasound. Gestational age should be determined by the first day of the last menstrual period (LMP), if available. If the LMP is unknown or uncertain, the gestational age should be based on clinical examination or ultrasound measurements.

Additionally, ACOG recommends that providers should use menstrual history to help determine the estimated due date (EDD). Providers should consider any discrepancies between menstrual dating and ultrasound as well as any other clinical findings when establishing an EDD.

ACOG also recommends that health care providers should not rely solely on menstrual history when determining gestational age and EDD, especially when there is a difference between the two. In such cases, a second trimester ultrasound should be performed to help refine gestational age and due date. Furthermore, a follow-up ultrasound may be necessary if the first trimester measurements are uncertain.

Finally, ACOG advises that late second and third trimester ultrasounds can be used to help confirm an EDD. This is especially important in cases where the estimated due date based on LMP or ultrasound differs significantly from the due date predicted by other methods. Overall, pregnancy dating can be difficult, and health care providers must use all available data to provide the most accurate EDD.