401072 Lecture Notes - Lecture 8: Preterm Birth, Gestational Age, Obstetrics
Document Summary
Gestational age is usually determined by the date of the woman"s last menstrual period, and assuming ovulation occurred on day fourteen of the menstural cycle. Sometimes a woman may be uncertain of the date of her last menstrual period, or there may be reason to suspect ovulation occurred signi cantly earlier or later than the fourteenth day of her cycle. Ultrasound scans offer an alternative method of estimating gestational age. The most accurate measurement for dating is the crown-rump length of the fetus, which can be done between 7 and 13 weeks of gestation. Not useful for dating, the abdominal circumference of the fetus may also be measured. This gives an estimate of the weight and size of the fetus and is important when doing serial ultrasounds to monitor fetal growth. The sex of the fetus may be discerned by ultrasound as early as 11 weeks" gestation. The accuracy is relatively imprecise when attempted early.
