Fetal Weight Extrapolation following a Third-Trimester Ultrasound Examination Using the Gestation-Adjusted Projection Method: A Systematic Review and Meta-analysis

Micah M. Vaughn-Valencia; Yan D. Zhao; Rodney K. Edwards; Shari Clifton; Hugh C. G. Nadeau

doi:10.1055/a-2628-2364

American Journal of Perinatology, Table of Contents

CC BY 4.0 · Am J Perinatol 2025; 42(15): 1940-1946
DOI: 10.1055/a-2628-2364

SMFM Fellowship Series Article

Fetal Weight Extrapolation following a Third-Trimester Ultrasound Examination Using the Gestation-Adjusted Projection Method: A Systematic Review and Meta-analysis

Authors

Micah M. Vaughn-Valencia

¹Section of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
Yan D. Zhao

²Department of Biostatistics and Epidemiology, Hudson College of Public Health, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
Rodney K. Edwards

³Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, College of Medicine, University of Florida, Gainesville, Florida
Shari Clifton

⁴Department of Health Sciences Library and Information Management, Graduate College, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
Hugh C. G. Nadeau

¹Section of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma

Abstract

Objective

Using systematic review and meta-analysis methodology, we sought to evaluate the accuracy of the gestation-adjusted projection (GAP) method of fetal weight extrapolation in the prediction of actual birth weight.

Study Design

A systematic literature search was performed using MEDLINE/PubMed, Embase, Scopus, and Web of Science for studies published from database inception to June 2023. Studies were compiled that assessed the accuracy of the GAP method in pregnant women at term (≥37 weeks gestation) with an ultrasound performed at 34 to 36 weeks gestation. Quality was assessed using the Newcastle–Ottawa scale, and risk of bias was assessed using the risk of bias in nonrandomized studies of interventions (ROBINS-I) tool. Meta-analysis was performed to evaluate the agreement between the GAP method and the actual birth weight using the mean percent error, mean absolute error, and mean absolute percent error. Means and 95% confidence intervals (95% CI) were calculated. Heterogeneity between studies was assessed using I ² and tau² statistics.

Results

The search identified 949 records. After a full-text review, a total of eight studies with 5,306 subjects were included. Studies were retrospective and prospective cohort studies. All studies were deemed high quality and determined to have a low risk of bias. Five studies were performed in the United States, one in Italy, one in Spain, and one in the United Kingdom. Four studies included patients with pregestational or gestational diabetes and obesity. Due to substantial heterogeneity, the random-effects model was used to estimate the effects of studies. The mean percent error was 3.1% (95% CI: 1.1–5.2), the mean absolute error was 240 g (95% CI: 205–275 g), and the mean absolute percent error was 8.0% (95% CI: 6.9–9.1).

Conclusion

The GAP method of fetal weight extrapolation is an accurate approach to birth weight prediction and is suitable for use in a diverse population. The study protocol was submitted for online registration in the International Register of Prospective Systematic Reviews (PROSPERO) before the literature review was undertaken (registration number: CRD42023392977).

Key Points

Estimation of fetal weight is useful for delivery planning.
The GAP method uses third-trimester ultrasound data.
The GAP method is an accurate approach to birth weight prediction.

Keywords

birth weight - estimated fetal weight - extrapolation - gestation-adjusted projection - meta-analysis - systematic review - ultrasound

Full Text

References

References
1 Colman A, Maharaj D, Hutton J, Tuohy J. Reliability of ultrasound estimation of fetal weight in term singleton pregnancies. N Z Med J 2006; 119 (1241): U2146
2 Nahum GG, Stanislaw H. Ultrasonographic prediction of term birth weight: how accurate is it?. Am J Obstet Gynecol 2003; 188 (02) 566-574
3 Pressman EK, Bienstock JL, Blakemore KJ, Martin SA, Callan NA. Prediction of birth weight by ultrasound in the third trimester. Obstet Gynecol 2000; 95 (04) 502-506
4 Lanowski JS, Lanowski G, Schippert C, Drinkut K, Hillemanns P, Staboulidou I. Ultrasound versus clinical examination to estimate fetal weight at term. Geburtshilfe Frauenheilkd 2017; 77 (03) 276-283
5 Paganelli S, Soncini E, Comitini G, Palomba S, La Sala GB. Sonographic fetal weight estimation in normal and overweight/obese healthy term pregnant women by gestation-adjusted projection (GAP) method. Arch Gynecol Obstet 2016; 293 (04) 775-781
6 Tuuli MG, Kapalka K, Macones GA, Cahill AG. Three-versus two-dimensional sonographic biometry for predicting birth weight and macrosomia in diabetic pregnancies. J Ultrasound Med 2016; 35 (09) 1925-1930
7 Stierman B, Afful J, Carroll MD. et al. National health and nutrition examination survey 2017-march 2020 prepandemic data files-development of files and prevalence estimates for selected health outcomes. Natl Health Stat Rep 2021; (158) 1-21
8 Driscoll AK, Gregory ECW. Increases in prepregnancy obesity: United States, 2016-2019. NCHS Data Brief 2020; (392) 1-8
9 Deputy NP, Kim SY, Conrey EJ, Bullard KM. Prevalence and changes in preexisting diabetes and gestational diabetes among women who had a live birth - United States, 2012-2016. MMWR Morb Mortal Wkly Rep 2018; 67 (43) 1201-1207
10 Gregory ECW, Ely DM. Trends and characteristics in prepregnancy diabetes: United States, 2016-2021. Natl Vital Stat Rep 2023; 72 (06) 1-13
11 Gaudet L, Ferraro ZM, Wen SW, Walker M. Maternal obesity and occurrence of fetal macrosomia: a systematic review and meta-analysis. BioMed Res Int 2014; 2014: 640291
12 Combs CA, Rosenn B, Miodovnik M, Siddiqi TA. Sonographic EFW and macrosomia: is there an optimum formula to predict diabetic fetal macrosomia?. J Matern Fetal Med 2000; 9 (01) 55-61
13 Malin GL, Bugg GJ, Takwoingi Y, Thornton JG, Jones NW. Antenatal magnetic resonance imaging versus ultrasound for predicting neonatal macrosomia: a systematic review and meta-analysis. BJOG 2016; 123 (01) 77-88
14 Njoku C, Emechebe C, Odusolu P, Abeshi S, Chukwu C, Ekabua J. Determination of accuracy of fetal weight using ultrasound and clinical fetal weight estimations in Calabar South, South Nigeria. Int Sch Res Notices 2014; 2014: 970973
15 Khani S, Ahmad-Shirvani M, Mohseni-Bandpei MA, Mohammadpour-Tahmtan RA. Comparison of abdominal palpation, Johnson's technique and ultrasound in the estimation of fetal weight in Northern Iran. Midwifery 2011; 27 (01) 99-103
16 Weiner E, Mizrachi Y, Fainstein N. et al. Comparison between three methods of fetal weight estimation during the active stage of labor performed by residents: a prospective cohort study. Fetal Diagn Ther 2017; 42 (02) 117-123
17 Ahmadzia HK, Thomas SM, Dude AM, Grotegut CA, Boyd BK. Prediction of birthweight from third-trimester ultrasound in morbidly obese women. Am J Obstet Gynecol 2014; 211 (04) 431.e1-431.e7
18 Mongelli M, Gardosi J. Gestation-adjusted projection of estimated fetal weight. Acta Obstet Gynecol Scand 1996; 75 (01) 28-31
19 Hadlock FP, Harrist RB, Martinez-Poyer J. In utero analysis of fetal growth: a sonographic weight standard. Radiology 1991; 181 (01) 129-133
20 Brenner WE, Edelman DA, Hendricks CH. A standard of fetal growth for the United States of America. Am J Obstet Gynecol 1976; 126 (05) 555-564
21 Schwartz RA, Simmonds LE, Rosenn B. Can a single preterm ultrasound accurately predict birth weight in gestational diabetes?. J Matern Fetal Neonatal Med 2016; 29 (01) 8-11
22 Moore GS, Post AL, West NA, Hart JE, Lynch AM. Fetal weight estimation in diabetic pregnancies using the gestation-adjusted projection method: comparison of two timing strategies for third-trimester sonography. J Ultrasound Med 2015; 34 (06) 971-975
23 Page MJ, McKenzie JE, Bossuyt PM. et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021; 372 (71) n71
24 Wells GA, Shea B, O'Connell D. et al. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses. Accessed June 12, 2025 at: https://www.ohri.ca/programs/clinical_epidemiology/oxford.asp
25 Sterne JA, Hernán MA, Reeves BC. et al. ROBINS-I: a tool for assessing risk of bias in non-randomised studies of interventions. BMJ 2016; 355: i4919
26 Best G, Pressman EK. Ultrasonographic prediction of birth weight in diabetic pregnancies. Obstet Gynecol 2002; 99 (5 Pt 1): 740-744
27 Thornburg LL, Barnes C, Glantz JC, Pressman EK. Sonographic birth-weight prediction in obese patients using the gestation-adjusted prediction method. Ultrasound Obstet Gynecol 2008; 32 (01) 66-70
28 Pagani G, Palai N, Zatti S, Fratelli N, Prefumo F, Frusca T. Fetal weight estimation in gestational diabetic pregnancies: comparison between conventional and three-dimensional fractional thigh volume methods using gestation-adjusted projection. Ultrasound Obstet Gynecol 2014; 43 (01) 72-76
29 Vila-Candel R, Soriano-Vidal FJ, Castro-Sánchez E. Third trimester ultrasound scan combined with a clinical method for accurate birthweight prediction at term: a cohort study in Spain. Rev Colomb Obstet Ginecol 2019; 70 (01) 27-38
30 Beta J, Khan N, Fiolna M, Khalil A, Ramadan G, Akolekar R. Maternal and neonatal complications of fetal macrosomia: cohort study. Ultrasound Obstet Gynecol 2019; 54 (03) 319-325
31 Dunn PM. A perinatal growth chart for international reference. Acta Paediatr Scand Suppl 1985; 319: 180-187