确定孕龄(GA)常有助于产科的临床处理,也可通过估计其他正常参数建立其标准。在末次月经不确定时,早期妊娠的妇科及超声检查结果常是确定晚期妊娠确切孕龄的非常可靠的参数。但有时并非如此简单,许多孕妇常在晚期妊娠时才来就诊,或在晚期妊娠时临床上发现了可疑病史。此时要准确估计孕龄,并以此决定是否继续或终止妊娠极为 Determining gestational age (GA) often contributes to the clinical management of obstetrics and can also establish its standard by estimating other normal parameters. Gynecological and ultrasonographic findings of early pregnancy are often very reliable parameters for determining the exact gestational age of late pregnancy when the last menstruation is uncertain. However, it is sometimes not so simple. Many pregnant women come to see a doctor often during late pregnancy or have a clinically suspicious medical history during late pregnancy. At this point to accurately estimate gestational age, and to decide whether to continue or terminate the pregnancy is extremely