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 Pregnancy Due Date and Gestational Age Calculator

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Calculate estimated due date (EDD) and gestational age based on :

Conception date
      (date of ovulation, egg retrieval, or insemination)
Date of 3-day embryo transfer
Date of 5-day embryo transfer
Due date by sonogram (reverse calculation)
First day of last menstrual period




Calculate Due Date From Ultrasound Report
 

 

The estimated due date (EDD or EDC) is the date that spontaneous onset of labor is expected to occur. The due date may be estimated by adding 280 days ( 9 months and 7 days) to the first day of the last menstrual period (LMP). This is the method used by "pregnancy wheels". The accuracy of the EDD derived by this method depends on accurate recall by the mother, assumes regular 28 day cycles, and that conception occurs on day 14 of the cycle. Use of the LMP to establish the due date may overestimate the duration of the pregnancy, and can be subject to an error of more than 2 weeks [5-7].

In cases where the date of conception is known precisely, such as with in vitro fertilization, the EDD is calculated by adding 266 days to the date of conception.

Ultrasound uses the size of the fetus to determine the gestational age (the time elapsed since the the first day of the last menstrual period). The accuracy of the ultrasound estimate of the gestational age varies according to the gestational age. "Ultrasound measurement of the embryo or fetus in the first trimester (up to and including 13 6/7 weeks of gestation) is the most accurate method to establish or confirm gestational age" [24].

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

  • Greater than 5 days before 9 0/7 weeks of gestation
  • Greater than 7 days from 9 0/7 weeks to 15 6/7 weeks
  • Greater than 10 days from 16 0/7 weeks to 21 6/7 weeks
  • Greater than 14 days from 22 0/7 weeks to 27 6/7 weeks
  • Greater than 21 days after 28 0/7 weeks. 

"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; they need to be guided by careful consideration of the entire clinical picture and may require closer surveillance, including repeat ultrasonography to ensure appropriate interval growth." [24].

Twins
When twin pregnancy is the result of in vitro fertilization determination of gestational age should be made from the date of embryo transfer. Otherwise date the pregnancy using the larger fetus [22,23]



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 [9].

Doppler Ultrasonography

The fetal heart can be heard using Doppler ultrasound by 10 to 12 weeks in most patients [10]. 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) [11-13]. The gestational age would, therefore, be at least 3 to 4 weeks at the time of a reliable hCG pregnancy test.
 

 


REFERENCES

1. Chervenak FA, Skupski DW, Romero R, et al: How accurate is fetal biometry in the assessment of fetal age?. Am J Obstet Gynecol 1998; 178:678.PMID:9579429
2. Mongelli M, Wilcox M, Gardosi J.: Estimating the date of confinement: ultrasonographic biometery versus certain menstrual dates. Am J Obstet Gynecol 1996; 174:278.PMID:8572021
3. Savitz DA, Terry Jr JW, Dole N, et al: Comparison of pregnancy dating by last menstrual period, ultrasound scanning, and their combination. Am J Obstet Gynecol 2002; 187:1660.PMID:12501080
4. ACOG Practice Bulletin. Clinical management guidelines for obstetricians-gynecologists. Number 55, September 2004 (replaces practice pattern number 6, October 1997). Management of Postterm Pregnancy.Obstet Gynecol. 2004;104:639-46.PMID:15339790
5. Kramer MS, McLean FH, Boyd ME, Usher RH: The validity of gestational age estimation by menstrual dating in term, preterm and postterm gestations. JAMA 1988; 260:3306. PMID:3054193
6. Savitz DA, Terry JW Jr, Dole N, Thorp JM Jr, Siega-Riz AM, Herring AH.Comparison of pregnancy dating by last menstrual period, ultrasound scanning, and their combination. Am J Obstet Gynecol. 2002 Dec;187(6):1660-6. PMID:12501080
7.Wilcox M, Gardosi J, Mongelli M, et al. Birth weight from pregnancies dated by ultrasonography in a multicultural British population. BMJ. Sep 4 1993;307(6904):588-91.PMID:8401014
8. Ultrasonography in Pregnancy. ACOG Practice Bulletin No. 98. American College of Obstetricians and Gynecologists. Obstet Gynecol 2008;112: 141944.
9. Rossavik IK, Fishburne JI. Conceptional age, menstrual age, and ultrasound age: a second-trimester comparison of pregnancies of known conception date with pregnancies dated from the last menstrual period. Obstet Gynecol. 1989 Feb;73(2):243-9.PMID: 2643067
10. Henderson SO, Mallon WK.Trauma in pregnancy. Emerg Med Clin North Am. 1998 Feb;16(1):209-28.PMID: 9496322
11. Hay DL, Lopata A.Chorionic gonadotropin secretion by human embryos in vitro. J Clin Endocrinol Metab. 1988 Dec;67(6):1322-4.PMID: 2461389
12. Wilcox AJ, et al. Time of implantation of the conceptus and loss of pregnancy.N Engl J Med. 1999 Jun 10;340(23):1796-9.PMID: 10362823
13. Lohstroh P, et al. Daily immunoactive and bioactive human chorionic gonadotropin profiles in periimplantation urine samples. Biol Reprod. 2006 Jul;75(1):24-33. PMID: 16525035
14.
Cervical insufficiency. ACOG Practice Bulletin No. 48. The American College of Obstetricians and Gynecologists. Obstet Gynecol 2003;102:10919. PMID: 15124633
15. Berghella V, et al., Does transvaginal sonographic measurement of cervical length before 14 weeks predict preterm delivery in high-risk pregnancies? Ultrasound Obstet Gynecol 2003;21:140-144. PMID: 12601834
16. Ultrasonography in Pregnancy. ACOG Practice Bulletin No. 101. American College of Obstetricians and Gynecologists. Obstet Gynecol 2009;113: 45161. PMID: 19155920
17. ACOG practice bulletin. Prevention of Rh D alloimmunization. Number 4, May 1999 (replaces educational bulletin Number 147, October 1990). Clinical management guidelines for obstetrician-gynecologists. American College of Obstetrics and Gynecology. Int J Gynaecol Obstet. 1999 Jul;66(1):63-70. PMID: 10458556
18. Fetal Lung Maturity. ACOG Practice Bulletin No. 97. American College of Obstetricians and Gynecologists. Obstet Gynecol 2008;112: 71726PMID: 18757686
19. ACOG practice bulletin. Antepartum fetal surveillance. Number 9, October 1999 (replaces Technical Bulletin Number 188, January 1994). Clinical management guidelines for obstetrician-gynecologists. Int J Gynaecol Obstet. 2000 Feb;68(2):175-85. PMID: 10717828
20. Institute for Clinical systems Improvement. Routine Prenatal Care. 13th ed. August 2009. Available at: http://www.icsi.org/prenatal_care_4/prenatal_care__routine__full_version__2.html
21. American College of Obstetricians and Gynecologists. ACOG Practice Bulletin No. 101: Ultrasonography in pregnancy. Obstet Gynecol. 2009 Feb;113(2 Pt 1):451-61. PMID: 19155920
22.Morin L, Lim K. Ultrasound in twin pregnancies. J Obstet Gynaecol Can. 2011 Jun;33(6):643-56. PMID: 21846456
23. Sperling L, Tabor A.Twin pregnancy: the role of ultrasound in management.Acta Obstet Gynecol Scand. 2001 Apr;80(4):287-99. PMID: 11264601
24. Method for estimating due date. Committee Opinion No. 611. Ameri-can College of Obstetricians and Gynecologists. Obstet Gynecol 2014;124:8636. PMID: 25244460

 

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