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Comment on “Predicting term birth weight using ultrasound and maternal characteristics” Eur J Obstet Gynecol Reprod Biol 2006;128(1–2):231–235.
European Journal of Obstetrics & Gynecology and Reproductive Biology 133 (2007) 119–122 www.elsevier.com/locate/ejogrb
LETTERS TO THE EDITOR—CORRESPONDENCE Comment on ‘‘Predicting term birth weight using ultrasound and maternal characteristics’’ Eur J Obstet Gynecol Reprod Biol 2006;128(1–2):231–235. Dear Editors, Prediction of term birth weight is important for clinical decision making and there is a vast amount of literature on how ultrasound and maternal characteristics can be used for such predictions. Halaska et al. [1] recently compared an ultrasound-based prediction formula of Shepard, Hadlock, a new equation, and Nahum’s equation based on maternal characteristics. Nahum’s equation was found to predict birth weight with the same accuracy to popular ultrasound-based formulas. Nahum et al. commented on these findings stating that birth weight depends on five important categories of variables—maternal characteristics, paternal factors, pregnancy-specific information, laboratory data and fetal ultrasound measurements [2]. In resource-limited countries the use of complicated formulas in not feasible and simple formulas are preferred whenever possible. Two popular equations are widely used in developing countries for term birth weight estimation— McDonald [3] and Johnson [4] (Table 1). The McDonald’s equation is limited by its low accuracy since it considers maternal abdominal circumference (AC) which is greatly influenced by body fat. Johnson’s equation has a higher accuracy but is slightly more complicated because it varies depending on whether or not there is engagement of the presenting part. We have reported our experience of using a new simple formula based on fundal height alone to determine term birth weight in a developing country setting [5]. We compared this new formula, BW (g) = 3 [FH (cm)]2, for estimating term birth weight with Johnson’s formula in a sample of 2000 women. This formula was found to be similar to Johnson’s formula in estimating foetal weight in our study population. The estimated birth weight using this formula was on average 251 g higher than the actual birth weight. We found that 69% of the estimated weight predictions were within 10% of actual birth weight. Similar findings have been reported with the use of Johnson’s formula which equally tends to over-estimate birth weight in all groups of babies. This new formula seems
Table 1 Formulae for predicting term birth weight in developing countries Author
Formula
McDonald Johnson
BW (g) = FH (cm) AC (cm) BW (g) = [FH (cm) n] 155 where n = 11 before engagement and n = 12 after engagemen BW (g) = 3 [FH (cm)]2
Kongnyuy and Mbu
Where BW = birth weight, FH = fundal height and AC = abdominal circumference.
to have great potential for application in resource-poor countries because it is simpler but equal in accuracy to the popular Johnson’s formula. There is need for validation of this new formula by assessing its accuracy in different populations both in developed as well as developing countries. References [1] Halaska MG, Vlk R, Felmar P, Hrehorcak M, Krcmar M, Mlcochova H, et al. Predciting term birth weight using ultrasound and maternal characteristics. Eur J Obstet Gynecol Reprod Biol 2006;128:135–231. [2] Stanislaw Harold, Nahum Gerard G. Comment on ‘‘Predicting term birth weight using ultrasound and maternal characteristics’’ [Eur J Gynecol Reprod Biol 128 (2006) 231-235]. Eur J Obstet Gynecol 2007;132:130–1. [3] Promvijit T, Suntharasaj T, Geater A. A comparison of Leopold’s Maneuver, McDonald’s measuremnt and ultrasonic estimation of fetal weight. In: The Proceedings of the 16th Annual Academic Meeting; 2000. [4] Numprasert W. A study in Johnson’s formula: fundal height measurement for estimation of birth weight. Au J T 2004;8:15–20. [5] Mbu RE, Ngoloko SHS, Kongnyuy EJ, Tonye RN, Nana PN, Ako SN, et al. The Validity of Kongnyuy–Mbu’s formula: A new approach in the estimation of foetal weight as from 35 weeks of gestation. Cameroon J Med 2003;12(1):13–4.
Eugene J. Kongnyuy,* Liverpool School of Tropical Medicine, RCOG International Office, Pembroke Place, L3 5QA Liverpool, UK Robinson E. Mbu Department of Gynaecology and Obstetrics, University of Yaounde I, Cameroon *Corresponding author. Tel.: +44 151 705 3705; fax: +44 151 705 3329 E-mail address: [email protected] (E.J. Kongnyuy) 30 January 2007
DOIs of original articles: 10.1016/j.ejogrb.2006.12.007., 10.1016/j.ejogrb.2006.12.008.
doi:10.1016/j.ejogrb.2007.02.015
0301-2115/$ – see front matter # 2007 Elsevier Ireland Ltd. All rights reserved.
LETTERS TO THE EDITOR—CORRESPONDENCE Comment on ‘‘Predicting term birth weight using ultrasound and maternal characteristics’’ Eur J Obstet Gynecol Reprod Biol 2006;128(1–2):231–235. Dear Editors, Prediction of term birth weight is important for clinical decision making and there is a vast amount of literature on how ultrasound and maternal characteristics can be used for such predictions. Halaska et al. [1] recently compared an ultrasound-based prediction formula of Shepard, Hadlock, a new equation, and Nahum’s equation based on maternal characteristics. Nahum’s equation was found to predict birth weight with the same accuracy to popular ultrasound-based formulas. Nahum et al. commented on these findings stating that birth weight depends on five important categories of variables—maternal characteristics, paternal factors, pregnancy-specific information, laboratory data and fetal ultrasound measurements [2]. In resource-limited countries the use of complicated formulas in not feasible and simple formulas are preferred whenever possible. Two popular equations are widely used in developing countries for term birth weight estimation— McDonald [3] and Johnson [4] (Table 1). The McDonald’s equation is limited by its low accuracy since it considers maternal abdominal circumference (AC) which is greatly influenced by body fat. Johnson’s equation has a higher accuracy but is slightly more complicated because it varies depending on whether or not there is engagement of the presenting part. We have reported our experience of using a new simple formula based on fundal height alone to determine term birth weight in a developing country setting [5]. We compared this new formula, BW (g) = 3 [FH (cm)]2, for estimating term birth weight with Johnson’s formula in a sample of 2000 women. This formula was found to be similar to Johnson’s formula in estimating foetal weight in our study population. The estimated birth weight using this formula was on average 251 g higher than the actual birth weight. We found that 69% of the estimated weight predictions were within 10% of actual birth weight. Similar findings have been reported with the use of Johnson’s formula which equally tends to over-estimate birth weight in all groups of babies. This new formula seems
Table 1 Formulae for predicting term birth weight in developing countries Author
Formula
McDonald Johnson
BW (g) = FH (cm) AC (cm) BW (g) = [FH (cm) n] 155 where n = 11 before engagement and n = 12 after engagemen BW (g) = 3 [FH (cm)]2
Kongnyuy and Mbu
Where BW = birth weight, FH = fundal height and AC = abdominal circumference.
to have great potential for application in resource-poor countries because it is simpler but equal in accuracy to the popular Johnson’s formula. There is need for validation of this new formula by assessing its accuracy in different populations both in developed as well as developing countries. References [1] Halaska MG, Vlk R, Felmar P, Hrehorcak M, Krcmar M, Mlcochova H, et al. Predciting term birth weight using ultrasound and maternal characteristics. Eur J Obstet Gynecol Reprod Biol 2006;128:135–231. [2] Stanislaw Harold, Nahum Gerard G. Comment on ‘‘Predicting term birth weight using ultrasound and maternal characteristics’’ [Eur J Gynecol Reprod Biol 128 (2006) 231-235]. Eur J Obstet Gynecol 2007;132:130–1. [3] Promvijit T, Suntharasaj T, Geater A. A comparison of Leopold’s Maneuver, McDonald’s measuremnt and ultrasonic estimation of fetal weight. In: The Proceedings of the 16th Annual Academic Meeting; 2000. [4] Numprasert W. A study in Johnson’s formula: fundal height measurement for estimation of birth weight. Au J T 2004;8:15–20. [5] Mbu RE, Ngoloko SHS, Kongnyuy EJ, Tonye RN, Nana PN, Ako SN, et al. The Validity of Kongnyuy–Mbu’s formula: A new approach in the estimation of foetal weight as from 35 weeks of gestation. Cameroon J Med 2003;12(1):13–4.
Eugene J. Kongnyuy,* Liverpool School of Tropical Medicine, RCOG International Office, Pembroke Place, L3 5QA Liverpool, UK Robinson E. Mbu Department of Gynaecology and Obstetrics, University of Yaounde I, Cameroon *Corresponding author. Tel.: +44 151 705 3705; fax: +44 151 705 3329 E-mail address: [email protected] (E.J. Kongnyuy) 30 January 2007
DOIs of original articles: 10.1016/j.ejogrb.2006.12.007., 10.1016/j.ejogrb.2006.12.008.
doi:10.1016/j.ejogrb.2007.02.015
0301-2115/$ – see front matter # 2007 Elsevier Ireland Ltd. All rights reserved.