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Estimation of birth weight and gestational age during the first two weeks of life among home deliveries
International Journal of Gynecology and Obstetrics 79 (2002) 255–257
Brief communication
Estimation of birth weight and gestational age during the first two weeks of life among home deliveries夞 F. Wabwire-Mangena, G. Kigozib, R.H. Grayc,* a
Institute of Public Health Makerere University, Kampala, Uganda Rakai Project, Uganda Virus Research Institute, Entebbe, Uganda c Department of Population and Family Health Sciences, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD, USA b
Received 3 July 2002; received in revised form 19 August 2002; accepted 21 August 2002
Keywords: Gestational age; Birth weight; Low birth weight; Preterm delivery; Head and chest circumference
Delayed observation of the newborn is a major constraint on research and clinical management of neonates in less developed countries. We analyzed data on infant weight, chest and head circumference, and gestational maturity for the first 14 days of life, among babies born in a large clinical trial in rural Uganda w1x. Women were enrolled during pregnancy, and a postpartum visit was conducted in the home. Infant weight was measured to the nearest 100 g. Head and chest circumference were measured using a non-elastic tape, and previous studies have shown these parameters can be used as a proxy measure for infant weight w2,3x. Gestational age was assessed by last normal menstrual period, and by the New Ballard Score w4x. There were 4033 enrolled mothers of whom 3777 were followed postpartum (93.7%). These 夞 The following investigators contributed substantively to this paper. M.J. Wawer, N.K. Sewankambo, D. Serwadda, L.H. Moulton, T. Lutalo, K.L. O’Brien. *Corresponding author. Suite 4030, Johns Hopkins University, School of Hygiene and Public Health, 615 N. Wolfe Street, Baltimore, MD 21205, USA. Tel.: q1-410-955-7818; fax: q1-410-614-7386. E-mail address: [email protected] (R.H. Gray).
women had 3541 live born infants of whom 3484 (98.4%) were singleton births. Among the 3484 singletons, 3159 infants (90.7%) were seen during the first 14 days of life and had an anthropometric assessment, and 3152 had a Ballard score assessment (90.5%). The date of the last normal menstrual period (LMP) was available for 2574 mothers of these singleton infants (73.9%), because fewer women could recall LMP dates. Only 45 infants (1.4%) were observed on the day of birth, and the majority (86.4%) were seen within the first week of life. The median interval between birth and observation was 2.04 days. We used natural cubic splines models to fit curves of anthropometric and gestational maturity measurements by age of the infant (in days). The intercept of the spline fitted curve (Int), the observed measures (Obsi) at each day i (is0–13 days after birth), and the spline estimate (Spli) for each day i was used to estimate the predicted measure on day of birth (Dob Meas), using the following equation: Dob MeassIntqObsiySpli . Mean weights declined from day 0 to day 2 of age and then increased progressively thereafter (Ps0.03, Fig. 1). Head circumference increased
0020-7292/02/$ - see front matter 䊚 2002 International Federation of Gynecology and Obstetrics. Published by Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 0 2 0 - 7 2 9 2 Ž 0 2 . 0 0 2 4 9 - 7
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F. Wabwire-Mangen et al. / International Journal of Gynecology and Obstetrics 79 (2002) 255–257
Fig. 1. Mean weight, head and chest circumference and gestational age estimates, by day of observation after birth.
progressively with age of the infant (Ps0.0001). The pattern of chest circumference was more complex, with small non-significant declines on the second day of life and after the 6th day of life. Gestational maturity as determined by the Ballard score was relatively stable by day of observation, showing a slight decline for infants assessed beyond the first week of life. The median gestational maturity was 40 weeks. The mean and median gestational ages based on LMP were close to 40 weeks and did not vary systematically by day of assessment. There were no significant differences between gestational maturity assessed by the Ballard score and by LMP. Using the spline models to extrapolate observed measurements to the day of birth, we estimate that the prevalence of low birth weight (-2500 g) was 10.7% (282y2632), and the prevalence of low birth weight inferred from the surrogate measure of chest circumference -30 cm w2x was 10.0% (267y2674). The prevalence of low birth weight based on the algorithm for head and chest circumference (head circumference F31 cm or head circumference )31 cm but chest circumference F30 cm) w3x was 10.8% (181y2606). Thus, the three measures provided comparable estimates of
the prevalence of low birth weight. The correlation coefficient between birthweight and chest circumference was rs0.62 (P-0.0001) and for head circumference the coefficient was rs0.52 (P0.0001). The prevalence of preterm delivery (37 weeks) based on the Ballard score was 10.8% (281y2607) and the prevalence of preterm based on LMP dates was 12.4% (147y1187). Anthropometric measurements and assessment of gestational maturity can be performed during the first two weeks of life and extrapolated to estimate these measurements on day of birth. Thus, in developing countries where home deliveries are common, and there are delays in observing infants after birth, delayed measurements can be used for investigation of pregnancy outcomes. Also, chest or head circumference can be used as surrogates for birth weight, and are logistically easier to obtain in a home setting than are measurements of infant weight. Acknowledgments This study was supported by grants RO1
F. Wabwire-Mangen et al. / International Journal of Gynecology and Obstetrics 79 (2002) 255–257
AI34826 and RO1 AI34826S, National Institute of Allergy and Infectious Diseases, grant 5P30HD06826, National Institute of Child Health and Development, grant 5D43TW00010 from the Fogarty Foundation, US National Institutes of Health; Rockefeller Foundation, grant 5024-30 from the John Snow Inc., Pfizer Inc., and the World Bank STI Project, Uganda. References w1x Gray RH, Wabwire-Mangen F, Kigozi G, Sewankambo
257
NK, Serwadda D, Moulton L, et al. Randomized trial of presumptive sexually transmitted disease therapy during pregnancy in Rakai, Uganda. Am J Obstet Gynecol 2001;185:1209 –1217. w2x WHO Collaborative Study of Birth Weight Surrogates. Use of a simple anthropometric measurement to predict birth weight. Bull WHO 1993;71:157 –163. w3x Raymond EG, Tafari N, Troendle JF, Clemens JD. Development of a practical screening tool to identify preterm, low-birthweight neonates in Ethiopia. Lancet 1994;344:520 –523. w4x Ballard JL, Khoury JC, Wedig K, Wang L, EllersWalsman BL, Lipp R. New Ballard Score, expanded to include extremely premature infants. J Pediatr 1991;119:417 –423.
Brief communication
Estimation of birth weight and gestational age during the first two weeks of life among home deliveries夞 F. Wabwire-Mangena, G. Kigozib, R.H. Grayc,* a
Institute of Public Health Makerere University, Kampala, Uganda Rakai Project, Uganda Virus Research Institute, Entebbe, Uganda c Department of Population and Family Health Sciences, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD, USA b
Received 3 July 2002; received in revised form 19 August 2002; accepted 21 August 2002
Keywords: Gestational age; Birth weight; Low birth weight; Preterm delivery; Head and chest circumference
Delayed observation of the newborn is a major constraint on research and clinical management of neonates in less developed countries. We analyzed data on infant weight, chest and head circumference, and gestational maturity for the first 14 days of life, among babies born in a large clinical trial in rural Uganda w1x. Women were enrolled during pregnancy, and a postpartum visit was conducted in the home. Infant weight was measured to the nearest 100 g. Head and chest circumference were measured using a non-elastic tape, and previous studies have shown these parameters can be used as a proxy measure for infant weight w2,3x. Gestational age was assessed by last normal menstrual period, and by the New Ballard Score w4x. There were 4033 enrolled mothers of whom 3777 were followed postpartum (93.7%). These 夞 The following investigators contributed substantively to this paper. M.J. Wawer, N.K. Sewankambo, D. Serwadda, L.H. Moulton, T. Lutalo, K.L. O’Brien. *Corresponding author. Suite 4030, Johns Hopkins University, School of Hygiene and Public Health, 615 N. Wolfe Street, Baltimore, MD 21205, USA. Tel.: q1-410-955-7818; fax: q1-410-614-7386. E-mail address: [email protected] (R.H. Gray).
women had 3541 live born infants of whom 3484 (98.4%) were singleton births. Among the 3484 singletons, 3159 infants (90.7%) were seen during the first 14 days of life and had an anthropometric assessment, and 3152 had a Ballard score assessment (90.5%). The date of the last normal menstrual period (LMP) was available for 2574 mothers of these singleton infants (73.9%), because fewer women could recall LMP dates. Only 45 infants (1.4%) were observed on the day of birth, and the majority (86.4%) were seen within the first week of life. The median interval between birth and observation was 2.04 days. We used natural cubic splines models to fit curves of anthropometric and gestational maturity measurements by age of the infant (in days). The intercept of the spline fitted curve (Int), the observed measures (Obsi) at each day i (is0–13 days after birth), and the spline estimate (Spli) for each day i was used to estimate the predicted measure on day of birth (Dob Meas), using the following equation: Dob MeassIntqObsiySpli . Mean weights declined from day 0 to day 2 of age and then increased progressively thereafter (Ps0.03, Fig. 1). Head circumference increased
0020-7292/02/$ - see front matter 䊚 2002 International Federation of Gynecology and Obstetrics. Published by Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 0 2 0 - 7 2 9 2 Ž 0 2 . 0 0 2 4 9 - 7
256
F. Wabwire-Mangen et al. / International Journal of Gynecology and Obstetrics 79 (2002) 255–257
Fig. 1. Mean weight, head and chest circumference and gestational age estimates, by day of observation after birth.
progressively with age of the infant (Ps0.0001). The pattern of chest circumference was more complex, with small non-significant declines on the second day of life and after the 6th day of life. Gestational maturity as determined by the Ballard score was relatively stable by day of observation, showing a slight decline for infants assessed beyond the first week of life. The median gestational maturity was 40 weeks. The mean and median gestational ages based on LMP were close to 40 weeks and did not vary systematically by day of assessment. There were no significant differences between gestational maturity assessed by the Ballard score and by LMP. Using the spline models to extrapolate observed measurements to the day of birth, we estimate that the prevalence of low birth weight (-2500 g) was 10.7% (282y2632), and the prevalence of low birth weight inferred from the surrogate measure of chest circumference -30 cm w2x was 10.0% (267y2674). The prevalence of low birth weight based on the algorithm for head and chest circumference (head circumference F31 cm or head circumference )31 cm but chest circumference F30 cm) w3x was 10.8% (181y2606). Thus, the three measures provided comparable estimates of
the prevalence of low birth weight. The correlation coefficient between birthweight and chest circumference was rs0.62 (P-0.0001) and for head circumference the coefficient was rs0.52 (P0.0001). The prevalence of preterm delivery (37 weeks) based on the Ballard score was 10.8% (281y2607) and the prevalence of preterm based on LMP dates was 12.4% (147y1187). Anthropometric measurements and assessment of gestational maturity can be performed during the first two weeks of life and extrapolated to estimate these measurements on day of birth. Thus, in developing countries where home deliveries are common, and there are delays in observing infants after birth, delayed measurements can be used for investigation of pregnancy outcomes. Also, chest or head circumference can be used as surrogates for birth weight, and are logistically easier to obtain in a home setting than are measurements of infant weight. Acknowledgments This study was supported by grants RO1
F. Wabwire-Mangen et al. / International Journal of Gynecology and Obstetrics 79 (2002) 255–257
AI34826 and RO1 AI34826S, National Institute of Allergy and Infectious Diseases, grant 5P30HD06826, National Institute of Child Health and Development, grant 5D43TW00010 from the Fogarty Foundation, US National Institutes of Health; Rockefeller Foundation, grant 5024-30 from the John Snow Inc., Pfizer Inc., and the World Bank STI Project, Uganda. References w1x Gray RH, Wabwire-Mangen F, Kigozi G, Sewankambo
257
NK, Serwadda D, Moulton L, et al. Randomized trial of presumptive sexually transmitted disease therapy during pregnancy in Rakai, Uganda. Am J Obstet Gynecol 2001;185:1209 –1217. w2x WHO Collaborative Study of Birth Weight Surrogates. Use of a simple anthropometric measurement to predict birth weight. Bull WHO 1993;71:157 –163. w3x Raymond EG, Tafari N, Troendle JF, Clemens JD. Development of a practical screening tool to identify preterm, low-birthweight neonates in Ethiopia. Lancet 1994;344:520 –523. w4x Ballard JL, Khoury JC, Wedig K, Wang L, EllersWalsman BL, Lipp R. New Ballard Score, expanded to include extremely premature infants. J Pediatr 1991;119:417 –423.