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Logos for the Society for Maternal-Fetal Medicine, the American College of Obstetricians and Gynecologists, and the Association for Medical Ultrasound

Leading Women’s Health Organizations Partner to Release Standardized Approach for Estimating Due Dates

New Guidelines Emphasize Importance of Consistency When Assigning Due Dates for Expecting Women

September 22, 2014

Washington, DC -- To promote consistency and accuracy among medical professionals when assigning due dates, the American College of Obstetricians and Gynecologists (the College), the American Institute of Ultrasound in Medicine (AIUM) and the Society for Maternal-Fetal Medicine (SMFM) jointly released new recommendations to estimate gestational age and the antic­ipated due date for pregnant women.

An accurately assigned estimated due date (EDD) is one of the most important factors that determines quality prenatal care, which includes timing of obstetric care, scheduling and interpretation of antepartum tests, and evaluation of fetal growth. An EDD also aids in designing interventions to prevent preterm birth, postterm birth, and other complications. A standard approach to determining EDDs also supports research and public health initiatives because of the importance of dates and timelines for protocols and vital statistics.

James D. Goldberg, MD, Vice Chair of the College’s Committee on Obstetric Practice, which developed the Committee Opinion, stressed the importance of consistency between institutions that provide obstetric care: “A uniform approach to assigning an EDD will be helpful for clinicians in all types of pregnancies, particularly with women who have had prior medical problems during pregnancy.”

“For some women, especially ones with early labor or other complications in the past, like a prior vertical cesarean incision, having an accurate due date is very important for making safe plans for care during their current pregnancy and for timing delivery, “ stated Joshua A. Copel, MD, the College’s Liaison Member from AIUM.

Sean C. Blackwell, MD, the College’s Liaison Member from SMFM, added, “This is good for our patients. There has been significant variability in the way different obstetrical providers calculated a women’s due date; and this standardization will allow for better consistency of care. This new standard may improve outcomes in high risk conditions that require scheduled delivery at term as well as in post-term pregnancies.”

Recommendations presented in the Committee Opinion include the following:

  • High-quality ultrasound measurement of the embryo or fetus in the first trimester is the most accurate method to establish or confirm gestational age.
  • If a pregnancy resulted from assisted reproductive technology (ART), the ART-derived gestational age should be used to assign the EDD. For instance, the EDD for a pregnancy resulting from in vitro fertilization should be established using the age of the embryo and the date of the transfer.
  • As soon as data from the last menstrual period (LMP), the first accurate ultrasound examination, or both are obtained, the gestational age and the EDD should be determined, discussed with the patient, and documented clearly in the medical record.
  • For the purposes of research and surveillance, the best obstetric estimate, rather than estimates based on the LMP alone, should be used as the measure for gestational age.
  • Subsequent changes to the EDD should be reserved for rare circumstances, discussed with the patient, and documented clearly in the medical record.


Committee Opinion #611, “Method for Estimating Due Date,” will be published in the October issue of Obstetrics & Gynecology.

See also Committee Opinion #579, “Definition of Term Pregnancy.”

The American College of Obstetricians and Gynecologists (The College), a 501(c)(3) organization, is the nation’s leading group of physicians providing health care for women. As a private, voluntary, nonprofit membership organization of approximately 58,000 members, The College strongly advocates for quality health care for women, maintains the highest standards of clinical practice and continuing education of its members, promotes patient education, and increases awareness among its members and the public of the changing issues facing women’s health care. The American Congress of Obstetricians and Gynecologists (ACOG), a 501(c)(6) organization, is its companion organization. www.acog.org

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