title: Nontraditional sonographic pearls in estimating gestational age.
abstract: Accurate gestational dating is one of the most important assessments obstetrical providers make in pregnancy, given that all of the various management strategies are dependent on knowing where the patient is in gestation. In addition to traditional biometry, ancillary biometric and nonbiometric measurements can help narrow the biologic variability between fetuses. Moreover, one can employ these nontraditional measurements both in late gestation to assist in determining appropriate gestational age and fetal lung maturity, and in other specific clinical situations-such as oligohydramnios, in which compression of the fetal head and abdomen can lead to difficulty in obtaining an accurate biparietal diameter and abdominal circumference. This chapter focuses on nontraditional fetal ultrasound measurements, including the transverse cerebellar diameter, fetal foot length, ratios of biometric and nonbiometric measurements, epiphyseal ossification centers, amniotic fluid volume, placental grading, and other miscellaneous markers in the context of evaluating a fetus with possible intrauterine growth restriction.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Colorado Health Sciences Center, UCDHSC, Academic Office 1, 12631 East 17th Avenue, Rm 4001, Aurora, CO 80045, USA. Amy.Gottlieb@uchsc.edu
authors.forename: Amy G
authors.initials: AG
authors.lastname: Gottlieb
authors.forename: Henry L
authors.initials: HL
authors.lastname: Galan
mesh_terms: D001699:Biometry / Q000379:methods*; D018568:Crown-Rump Length; D005260:Female; D005317:Fetal Growth Retardation / Q000175:diagnosis* / Q000000981:diagnostic imaging; D005333:Fetus / Q000033:anatomy & histology* / Q000196:embryology / Q000502:physiology; D005528:Foot / Q000033:anatomy & histology; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D012016:Reference Values; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal / Q000379:methods*