Methods for Estimating the Due Date - ACOG
Calculate delivery due date, gestational age and other important dates " Ultrasound measurement of the embryo or fetus in the first trimester (up to and . of this site shall be liable for any special, consequential, or exemplary damages. identified through searching the websites of health technology assessment and health . CRL crown-rump length. EDD estimated due date. FL femur length. HC. ultrasonographers in CRL measurement. Please read Dating chart for fetal CRL used in INTERGROWTH st However, different sites and.
Briefly, we recruited women from the selected populations with no clinically relevant obstetric or gynecological history, who met the entry criteria of optimal health, nutrition, education and socioeconomic status to create a group of affluent, clinically healthy women who were at low risk of intrauterine growth restriction and preterm birth. The women, who were all well-educated and living in urban areas, reported the date and certainty of their LMP at their first antenatal clinic visit in response to specific questions.
However, as the first contact with the study often occurred at several different clinics in the geographical area, it was considered acceptable to use other, locally available, machines for the CRL measurement at the first antenatal visit only, provided that they were evaluated and approved by the study team.
All 39 ultrasonographers at the eight study sites underwent rigorous training and standardization specifically for CRL measurement The ultrasonographers were only certified to measure CRL in the study if they demonstrated adequate knowledge of the study protocol and the quality of the images submitted for review was satisfactory CRL was measured once using strict techniques and imaging criteria Statistical methods The sample size was based principally on the precision and accuracy of a single centile and regression-based reference limits 19 We have shown that with a sample ofwe would obtain a precision of 0.
Further details on the precision obtained at the 5th or 10th centile by sample size ranging from to are provided in a previous publication We determined a mean target sample of women per site, after excluding complicated pregnancies and those lost to follow-up 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.
The statistical methods used are described in detail elsewhere Mean sac diameter measurements are not recommended for estimating the due date.
Dating changes for smaller discrepancies are appropriate based on how early in the first trimester the ultrasound examination was performed and clinical assessment of the reliability of the LMP date Table 1. For example, for a day-5 embryo, the EDD would be days from the embryo replacement date.First Ultrasound at 6 weeks 3 days
Likewise, the EDD for a day-3 embryo would be days from the embryo replacement date. Clinical Considerations in the Second Trimester Using a single ultrasound examination in the second trimester to assist in determining the gestational age enables simultaneous fetal anatomic evaluation.
With rare exception, if a first-trimester ultrasound examination was performed, especially one consistent with LMP dating, gestational age should not be adjusted based on a second-trimester ultrasound examination.
Ultrasonography dating in the second trimester typically is based on regression formulas that incorporate variables such as the biparietal diameter and head circumference measured in transverse section of the head at the level of the thalami and cavum septi pellucidi; the cerebellar hemispheres should not be visible in this scanning plane the femur length measured with full length of the bone perpendicular to the ultrasound beam, excluding the distal femoral epiphysis the abdominal circumference measured in symmetrical, transverse round section at the skin line, with visualization of the vertebrae and in a plane with visualization of the stomach, umbilical vein, and portal sinus 8 Other biometric variables, such as additional long bones and the transverse cerebellar diameter, also can play a role.
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. 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.
The best available data support adjusting the EDD of a pregnancy if the first ultrasonography in the pregnancy is performed in the third trimester and suggests a discrepancy in gestational dating of more than 21 days. Conclusion Accurate dating of pregnancy is important to improve outcomes and is a research and public health imperative. As soon as data from the 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.
The American College of Obstetricians and Gynecologists, the American Institute of Ultrasound in Medicine, and the Society for Maternal—Fetal Medicine recognize the advantages of a single dating paradigm being used within and between institutions that provide obstetric care.
Women's Health Care Physicians
Table 1 provides guidelines for estimating the due date based on ultrasonography and the LMP in pregnancy, and provides single-point cutoffs and ranges based on available evidence and expert opinion.
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Int J Gynaecol Obstet ; First trimester ultrasound screening is effective in reducing postterm labor induction rates: Ultrasound for fetal assessment in early pregnancy. Cochrane Database of Systematic ReviewsIssue 7.
Hay DL, Lopata A. Chorionic gonadotropin secretion by human embryos in vitro. J Clin Endocrinol Metab. Wilcox AJ, et al. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med. Lohstroh P, et al. Daily immunoactive and bioactive human chorionic gonadotropin profiles in periimplantation urine samples. The American College of Obstetricians and Gynecologists.
Crown-rump length - Wikipedia
Berghella V, et al. Ultrasound Obstet Gynecol ; Prevention of Rh D alloimmunization. Number 4, May replaces educational bulletin NumberOctober Clinical management guidelines for obstetrician-gynecologists.
American College of Obstetrics and Gynecology.
Int J Gynaecol Obstet. Institute for Clinical systems Improvement. Morin L, Lim K.