Human chorionic gonadotropin as a measure of pregnancy duration.
OBJECTIVE
To compare gestational age (GA) estimates in early pregnancy, determined by last menstrual period (LMP), human chorionic gonadotropin (hCG) concentration, ultrasound crown-rump length (Hadlock formula), and ovulation day (luteinizing hormone surge plus 1day).


METHODS
Female volunteers seeking to conceive (at 5 US sites) collected daily early-morning urine for up to 3 menstrual cycles. Pregnant women underwent ultrasound dating scans. Conception cycle urine was quantitatively assessed for luteinizing hormone and hCG. Summary statistics for GA using each reference method were determined (n=131).


RESULTS
Correlation between GA determined by ultrasound and ovulation day was excellent (maximum difference 10days); however, pregnancies dated by ultrasound were 3days advanced. The difference between LMP estimates and estimates based on ovulation day or ultrasound was 9 and 12days, respectively. A uniform rise in hCG on each day of pregnancy was seen using all reference methods. The accuracy of hCG measurement in determining the week since conception was more than 93%.


CONCLUSIONS
Methods for establishing pregnancy duration vary in their accuracy and their GA estimates. The rise in hCG concentration in early pregnancy is uniform and therefore hCG levels provide the most accurate, early estimation of GA in single, viable pregnancies. ClinicalTrials.gov:NCT01077583.
Department of Obstetrics and Gynecology, George Washington University Medical Center, Washington, USA.
John
J
Larsen
Philip
P
Buchanan
Sarah
S
Johnson
Sonya
S
Godbert
Michael
M
Zinaman
D000293:Adolescent; D000328:Adult; D006063:Chorionic Gonadotropin / Q000652:urine*; D018568:Crown-Rump Length; D005260:Female; D005865:Gestational Age; D006801:Humans; D007986:Luteinizing Hormone / Q000652:urine*; D008597:Menstrual Cycle / Q000502:physiology; D008875:Middle Aged; D010060:Ovulation / Q000502:physiology; D011247:Pregnancy; D011446:Prospective Studies; D055815:Young Adult
D006063:Chorionic Gonadotropin; D007986:Luteinizing Hormone
Gestational age; Human chorionic gonadotropin; Pregnancy