Article

Assessing the value of customized birth weight percentiles.

Department of Obstetrics and Gynaecology, University of British Columbia, Vancouver, Canada.
American journal of epidemiology (impact factor: 5.59). 02/2011; 173(4):459-67. DOI:10.1093/aje/kwq399 pp.459-67
Source: PubMed

ABSTRACT Customized birth weight percentiles are weight-for-gestational-age percentiles that account for the influence of maternal characteristics on fetal growth. Although intuitively appealing, the incremental value they provide in the identification of intrauterine growth restriction (IUGR) over conventional birth weight percentiles is controversial. The objective of this study was to assess the value of customized birth weight percentiles in a simulated cohort of 100,000 infants aged 37 weeks whose IUGR status was known. A cohort of infants with a range of healthy birth weights was first simulated on the basis of the distributions of maternal/fetal characteristics observed in births at the Royal Victoria Hospital in Montreal, Canada, between 2000 and 2006. The occurrence of IUGR was re-created by reducing the observed birth weights of a small percentage of these infants. The value of customized percentiles was assessed by calculating true and false positive rates. Customizing birth weight percentiles for maternal characteristics added very little information to the identification of IUGR beyond that obtained from conventional weight-for-gestational-age percentiles (true positive rates of 61.8% and 61.1%, respectively, and false positive rates of 7.9% and 8.5%, respectively). For the process of customization to be worthwhile, maternal characteristics in the customization model were shown through simulation to require an unrealistically strong association with birth weight.

0 0
 · 
0 Bookmarks
 · 
32 Views
  • Source
    Article: Individually customised fetal weight charts derived from ultrasound measurements: the Generation R Study.
    Romy Gaillard, Maria A J de Ridder, Bero O Verburg, Jacqueline C M Witteman, Johan P Mackenbach, Henriëtte A Moll, Albert Hofman, Eric A P Steegers, Vincent W V Jaddoe
    [show abstract] [hide abstract]
    ABSTRACT: Maternal and fetal characteristics are important determinants of fetal growth potential, and should ideally be taken into consideration when evaluating fetal growth variation. We developed a model for individually customised growth charts for estimated fetal weight, which takes into account physiological maternal and fetal characteristics known at the start of pregnancy. We used fetal ultrasound data of 8,162 pregnant women participating in the Generation R Study, a prospective, population-based cohort study from early pregnancy onwards. A repeated measurements regression model was constructed, using backward selection procedures for identifying relevant maternal and fetal characteristics. The final model for estimating expected fetal weight included gestational age, fetal sex, parity, ethnicity, maternal age, height and weight. Using this model, we developed individually customised growth charts, and their corresponding standard deviations, for fetal weight from 18 weeks onwards. Of the total of 495 fetuses who were classified as small size for gestational age (<10th percentile) when fetal weight was evaluated using the normal population growth chart, 80 (16%) were in the normal range when individually customised growth charts were used. 550 fetuses were classified as small size for gestational age using individually customised growth charts, and 135 of them (25%) were classified as normal if the unadjusted reference chart was used. In conclusion, this is the first study using ultrasound measurements in a large population-based study to fit a model to construct individually customised growth charts, taking into account physiological maternal and fetal characteristics. These charts might be useful for use in epidemiological studies and in clinical practice.
    European Journal of Epidemiology 11/2011; 26(12):919-26. · 4.71 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

Keywords

birth weight
 
birth weight percentiles
 
conventional birth weight percentiles
 
conventional weight-for-gestational-age percentiles
 
customization model
 
Customized birth weight percentiles
 
Customizing birth weight percentiles
 
false positive rates
 
healthy birth weights
 
incremental value
 
intrauterine growth restriction
 
intuitively appealing
 
IUGR status
 
maternal characteristics
 
maternal/fetal characteristics
 
observed birth weights
 
Royal Victoria Hospital
 
simulated cohort
 
true positive rates
 
unrealistically strong association