Recommendations The American College of Obstetricians and Gynecologists, the American Institute of Ultrasound in Medicine, and the Society for Maternal—Fetal Medicine make the following recommendations regarding the method for estimating gestational age and due date: We also excluded mothers diagnosed with catastrophic or very severe medical conditions, those with severe unanticipated pregnancy-related conditions requiring hospital admission and those identified during pregnancy who no longer fulfilled all the entry criteria. Evidence of early first-trimester growth restriction in pregnancies that subsequently end in miscarriage. Fourthly, only healthy women sampled from preselected, geographically defined populations with low adverse perinatal outcome rates were selected. Conversely, an apparently reliable and accurate LMP with a substantial difference in estimated GA based on CRL should be considered as an indicator of possible growth disturbance or underlying pathology that needs to be monitored and corroborated 31
For instance, the EDD for a pregnancy that resulted from in vitro fertilization should be assigned using the age of the embryo and the date of transfer.
Women's Health Care Physicians
The following supporting information may be found in the online version of this article. American College of Obstetricians and Gynecologists. An accurately assigned EDD early in prenatal care is among the most important results of evaluation and history taking. This article has been cited by other articles in PMC. Because of the risk of redating a small fetus that may be growth restricted, management decisions based on third-trimester ultrasonography alone are especially problematic; therefore, decisions need to be guided by careful consideration of the entire clinical picture and may require close surveillance, including repeat ultrasonography, to ensure appropriate interval growth.
Last menstrual period versus ultrasound for pregnancy dating. J Clin Ultrasound ; Date changes for smaller discrepancies 10—14 days are appropriate based on how early in this second-trimester range the ultrasound examination was performed and on clinician assessment of LMP reliability. The measurement used for dating should be the mean of three discrete CRL measurements when possible and should be obtained in a true midsagittal plane, with the genital tubercle and fetal spine longitudinally in view and the maximum length from cranium to caudal rump measured as a straight line 8, The participating hospitals included: However, in a proportion of pregnancies, depending on the locality, the LMP is unknown or the information is unreliable 67.