The accuracy of the ultrasound estimate of the gestational age varies according to the gestational age. The Society of Obstetricians and Gynaecologists of Canada recommends the earliest ultrasound with a crown rump length equivalent to at least 7 weeks or 10 mm should be used to determine the gestational age . The American College of Obstetricians and Gynecologists recommends that ultrasound-established dates should take preference over menstrual dates when the discrepancy between ultrasound dating and LMP is.
Other Methods For Estimating the Gestational Age Clinical Examination A pelvic examination supported by good menstrual records in the first trimester has been reported to be a reliable method for dating of pregnancy . Doppler Ultrasonography The fetal heart can be heard using Doppler ultrasound by 10 to 12 weeks in most patients .
The gestational age should ,therefore, be at least 10 to 12 weeks if fetal heart tone are heard. Human Chorionic Gonadotropin Pregnancy Test Human chorionic gonadotropin first becomes detectable in the mother's blood and urine between 6 and 14 days after fertilization 3 to 4 weeks gestational age . The gestational age would, therefore, be at least 3 to 4 weeks at the time of a reliable hCG pregnancy test.
Twins When a twin pregnancy is the result of in vitro fertilization determination of gestational age should be made from the date of embryo transfer.
The table below shows the average age of infants delivered in the United States according to the number of fetuses being carried plurality . The earlier age at delivery of multiple gestations is a reflection of the increased incidence of preterm labor and obstetric intervention for complications such as preeclampsia, abruptio placentae, fetal growth restriction, and increased risk for stillbirth that occurs as the number of fetuses increases .
The tendency for multiple gestations to be delivered earlier than singleton pregnancies should not be interpreted that multiples should be assigned an earlier estimated due date. How accurate is fetal biometry in the assessment of fetal age?.
Methods for Estimating the Due Date
Am J Obstet Gynecol ; Estimating the date of confinement: Comparison of pregnancy dating by last menstrual period, ultrasound scanning, and their combination. Clinical management guidelines for obstetricians-gynecologists.
Number 55, September replaces practice pattern number 6, October Management of Postterm Pregnancy. The validity of gestational age estimation by menstrual dating in term, preterm and postterm gestations. Am J Obstet Gynecol. Birth weight from pregnancies dated by ultrasonography in a multicultural British population.
Due Date Calculator
Sep 4 ; American College of Obstetricians and Gynecologists. Conceptional age, menstrual age, and ultrasound age: Enter last menstrual period LMP , current gestational age GA , OR expected due date to determine the other two, plus estimated date of conception. Please fill out required fields.
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Women's Health Care Physicians
Med treatment and more Treatment. Fetal Imaging Workshop Invited Participants. A comparison of recalled date of last menstrual period with prospectively recorded dates. J Womens Health Larchmt ; Comparison of pregnancy dating by last menstrual period, ultrasound scanning, and their combination. Am J Obstet Gynecol ; Last menstrual period versus ultrasound for pregnancy dating. Int J Gynaecol Obstet ; First trimester ultrasound screening is effective in reducing postterm labor induction rates: Ultrasound for fetal assessment in early pregnancy.
Pregnancy Gestation by LMP and Ultrasound Biometry
Cochrane Database of Systematic Reviews , Issue 7. Predicting delivery date by ultrasound and last menstrual period in early gestation. New charts for ultrasound dating of pregnancy and assessment of fetal growth: Ultrasound Obstet Gynecol ; First- and second-trimester ultrasound assessment of gestational age.
First- vs second-trimester ultrasound: Br J Obstet Gynaecol ; Gestational age in pregnancies conceived after in vitro fertilization: Ultrasound dating at 12—14 weeks of gestation. A prospective cross-validation of established dating formulae in in-vitro fertilized pregnancies. Accuracy of gestational age estimation by means of fetal crown—rump length measurement. Estimation of gestational age by transvaginal sonographic measurement of greatest embryonic length in dated human embryos. Ultrasound Obstet Gynecol ;4: Underestimation of gestational age by conventional crown—rump length dating curves.
New crown—rump length curve based on over pregnancies.
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Standardization of sonar cephalometry and gestational age. Sonographic prediction of gestational age: Conceptional age, menstrual age, and ultrasound age:
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