Fetal growth assessment - decision support

Fetal health assessment - decision support

Dating to the CESDI (UK) rule. Programme written by DJR Hutchon copyright Requires Internet Explorer 4.0 or above (or equivalent) for calculator to work. Year 2000 compliant. If Serum screen or nuchal thickness not available, (or less than 1 mm) leave blank. Only valid for calculating Down risk for CRL 38 - 84mm and BPD 28 to 50mm. These calculations assume that the NT measurements for CRL are made using the same protocol as the Fetal Medicine Foundation, and for BPD as described by Benacerraf et al (1987). Using Hecht and Hook Down risk formula Instruction for using OFFLINE . . . HOME PAGE

CRL using Smith et al formula REFERENCES  UK date system  ie date/month/year (4 digits for year)
Patient's ID (Optional) Date of Birth (Mandatory)
Last period date Are you sure? Yes - - - Normal cycle length Default is 28 days
Date of dating scan Nuchal thickness mm. MoM=LR= Down serum screen risk 1:
Enter CRL measurement mm mm or BPD mm (ENTER ONLY ONE) Equiv to wks + days
Nasal bone seen 11-14 wks y/n (leave blank if not looked for)
Age alone Down syndrome (DS) risk at birth 1: Integrated Down syndrome (DS) risk at birth 1:
Age alone DS risk at date of scan 1: Integrated DS risk at date of scan 1: (includes nasal bone if entered)
EDD by LMP by SCAN 42 wks on
Best EDD is
Elective delivery inadvisable before 14% risk of labour before this date.
Trisomy 18 risk at 9-14wks= 1 in at 15-20 wks= 1 in at birth= 1 in
Trisomy 13 risk at 9-14wks= 1 in at 15-20 wks= 1 in at birth= 1 in
Gestation by scan on date is wks +days.

Fetal health assessment - expert system

Enter date of scan, measurements, AFI and umbilical artery RI if available

First || Second || Third Normal
growth scan Z || growth scan Z || growth scan Z +1.645 to
Date score || Date score || Date score -1.645
HC || HC || HC
AC || AC || AC
FL || FL || FL
Gestation wks || wks || wks
Est fetal wt Kg || Kg || Kg
Umb Art RI

Normal range for Z score is -1.645 to +1.645. This calculator is for educational use. It is believed accurate but no responsibility for accuracy of the results is accepted by the author. The calculations assume that there is no correlation between absent nasal bones and other risk factors for Down syndrome used in the calculator. David J R Hutchon BSc, MB, ChB, FRCOG Consultant Obstetrician, Memorial Hospital, Darlington, England.

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Go to paper on proposal for valid customised charts generation ("Back to the future for Hermanni Boerhaave" published by OBGYN.NET)

Comments and suggestions are welcome and will be included in the comments section.


This Web page is at www.hutchon.freeserve.co.uk/GrowthdownUKhookBPDnasal.htm
1. Smith GCS, Smith MFS, McNay MB and Flemming JEE First-trimester growth and the risk of low birth weight New England Journal of Medicine 1998;339:1817-22

2. Kurmanavicius J, Wright EM, Royston P, Zimmermann R, Huch R, Huch A, Wisser J. Fetal ultrasound Biometry: 1. Head reference values. British Journal of Obstetrics and Gynaecology. 1999 106:126-135
3. Kurmanavicius J, Wright EM, Royston P, Zimmermann R, Huch R, Huch A, Wisser J. Fetal ultrasound Biometry: 2. Abdomen and femur length reference values. British Journal of Obstetrics and Gynaecology. 1999 106:136-143

4. Moore T R and Cayle J E. The amniotic fluid index in normal human pregnancy. American Journal of Obstetrics and Gynecology 1990;162:1168-73
5. Cuckle H S, & Schmi I Calculating correct Down's syndrome risks. British Journal of Obstetrics and Gynaecology 1999;106:371-372
6. Wald N J, Watt H C, & Hackshaw A K. Integrated screening for Down's Syndrome based on tests performed during the first and second trimester The New England Journal of Medicine 1999;341(7):461-467
7. Pandya P P, Johnson S, Malligianis P, and Nicolaides K H. First Trimester fetal nuchal translucency and screening for chromosomal abnormalities. Ultrasound and early pregnancy Chapter 7
8. Snijders R J M, Holzgreve W, Cuckle H and Nicolaides K H. Maternal age-specific risks for trisomies at 9-14 weeks gestation. Prenatal Diagnosis (1994) 13:543-552 For the purposes of the calculator I have assumed a uniform loss of pregnancies with trisomy 13 and 18 as a result to miscarriage between 9 and 14 weeks and 15 and 20 weeks.
9. Snijders R J M, Sundberg K, Holzgreve W, Henry G, and Nocolaides K H. Maternal age- and gestation specific risk for trisomy 21. Ultrasound in Obstetrics and Gynaecology 1999;13:167-170
10. Zosmer N, Souter V L, Chan C S Y, Huggon I C and Nicolaides K H. Early diagnosis of major cardiac defects in chromosomally normal fetuses with increased nuchal translucency. Brtish Journal of Obstetrics and Gynaecology 1999;106:829-833
11. Madar J, Richmond S & Hey E. surfactant deficient respiratory distress after elective delivery at 'term'. Northern Region Maternity Survey Meeting 1999. Accepted for publication in Acta Paediatrica
12. Hyett J A, Noble P L, Snijders R J M, Montenegro N, & Nicolaides K H. Fetal heart rate in trisomy 21 and other chromosomal abnormalities at 10 - 14 weeks of gestation. Ultrasound Obstet Gynecol 7 (1996) 239-244
13. Hecht C A & Hook EB the imprecision in rates of Down syndrome. (1994) Prenatal Diag 14:729-738
14. Larsen T, Nguyen T H, Greisen G, Engholm G & Moller H. does discrepancy between gestational age determined by biparietal diameter and last menstrual period sometimes signify early intrauterine groath retardation? BJOG 2000,107(2) 235-244
15. Gardosi & Francis A. Early pregnancy predictors of preterm birth: the role of a prolonged menstruation-conception interval. BJOG 2000,107(2),228-237
16. Stiller R J, Lieberson D, Herzlinger R, Siddiqui D, Laifer S A, & Whetham J C G. The association of increased nuchal translucency and spinal muscular atrophy type 1. Prenatal Diagnosis 1999;19:587-589
17. Locatelli A, Piccoli M G, Vergani P, Mariani E, Ghidini A, Mariani S, Pezzullo J. Critical appraisal of the use of nuchal thickness measurements for the predicition of Down syndrome. Am J Obstet Gynecol 2000;182:192-197 The authors point out that caution should be used in the use of the proposed liklihood ratios until other markers such as serum tests are proved to be independent of each other.
18. Nicholaides K H, Snijders R J M, and Cuckle H S Correct estimation of parameters for ultrasound nuchal translucency screening. Prenatal Diagnosis 1998 18;511-523
19. Benacerraf BR, Gelman R, Frigoletto Jr FD Sonographic identification of second-trimester fetuses with Down's syndrome. 1987;317:1371-1376
20. Altman D G and Chitty L S. New cahrts for ultrasound dating of pregnancy Ultrasound Obstet Gynecol 10 (1997) 174 - 191
21. Cicero S et al Absence of nasal bone in fetuses with trisomy 21 at 11 to 14 weeks of gestation: an observational study.(2001) The Lancet 358;1665-1667 I am grateful to Professor Howard Cuckle for information on the Gaussian LR equation for a single variable.
This risk assumes no previous affected pregnancy. A previous affected pregnancy increases the risk further, to about 1 in 200 at age 30 and 1 in 25 at age 45.
The maternal age specific incidence of trisomy 21 at birth is 54% lower than at 9-14 weeks of gestation. NT measurements in the second trimester should be carrried out in the transverse plane using the technique of Benacerraf et al. BPD measured from outer to inner edge of skull.


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