Hadlock dating criteria
The rise in h CG concentration in early pregnancy is uniform and therefore h CG levels provide the most accurate, early estimation of GA in single, viable pregnancies.
Obstetric ultrasonography is an important and common part of obstetric care in the United States.
The purpose of this document is to present information and evidence regarding the methodology of, indications for, benefits of, and risks associated with obstetric ultrasonography in specific clinical situations.
Portions of this Practice Bulletin were developed from collaborative documents with the American College of Radiology and the American Institute of Ultrasound in Medicine (1, 2).
These guidelines should not be construed as dictating an exclusive course of treatment or procedure.
This Practice Bulletin was developed by the American College of Obstetricians and Gynecologists’ Committee on Practice Bulletins–Obstetrics and the American Institute of Ultrasound in Medicine in collaboration with Lynn L. The information is designed to aid practitioners in making decisions about appropriate obstetric and gynecologic care.The accuracy of h CG measurement in determining the week since conception was more than 93%.Methods for establishing pregnancy duration vary in their accuracy and their GA estimates.The American College of Obstetricians and Gynecologists 409 12th Street, SW, PO Box 96920, Washington, DC 20090-6920 Ultrasound in pregnancy. The choice of transducer frequency is a trade-off between beam penetration and resolution.Crown rump length (CRL) is the length of the embryo or fetus from the top of its head to bottom of torso.