Comparison of estimated fetal weight percentiles near term for predicting extremes of birthweight percentile

Abstract

BACKGROUND: The INTERGROWTH-21st estimated fetal weight percentiles are recommended for predicting extremes of birthweight percentile, although evidence for their superiority over the widely employed Hadlock method is lacking. OBJECTIVE: This study aimed to compare the ability of estimated fetal weight percentiles calculated using the Hadlock method and the INTERGROWTH-21st method to predict extremes of birthweight percentile. STUDY DESIGN: A prospective cohort study of blinded serial ultrasonography in nulliparous women with a singleton pregnancy, The Pregnancy Outcome Prediction study was conducted in Cambridge, United Kingdom. The study participants who had a research estimated fetal weight performed at 36 weeks' gestation were eligible for the analysis. Estimated fetal weight percentiles for gestational age calculated using (1) the Hadlock method or (2) the INTERGROWTH-21st method were used as exposures. Birthweight percentiles of <10th (small for gestational age) and >90th (large for gestational age) for gestational age and fetal sex using the United Kingdom 1990 reference or the INTERGROWTH-21st birthweight reference were analyzed as outcomes using receiver operating characteristic curve analysis. Screening statistics from 2Â2 tables were calculated for dichotomized exposures and each outcome. RESULTS: The Hadlock estimated fetal weight percentile performed better than the INTERGROWTH-21st estimated fetal weight percentile at discriminating both small for gestational age birthweight (areas under the receiver operating characteristic curves, 0.87 vs 0.85; 95% confidence intervals, 0.85e0.89 vs 0.83e0.87, respectively; P<.0001) and large for gestational age birthweight (areas under the receiver operating characteristic curves, 0.87 vs 0.86; 95% confidence intervals, 0.85e0.90 vs 0.83e0.89, respectively; P¼.005). When the estimated fetal weight percentiles were dichotomized and screen positive was defined at 90% specificity, the sensitivity for the Hadlock vs the INTERGROWTH-21st method was 58.6% vs 52.3%, respectively, for small for gestational age, and 71.0% vs 60.9%, respectively, for birthweight at less than the third percentile (United Kingdom 1990 reference). The results were similar when the birthweight percentile was defined using the INTERGROWTH-21st birthweight reference, when the estimated fetal weight was calculated without the inclusion of head measurements, or when the women who had clinically indicated scans and women who had their research scan result were excluded. CONCLUSION: Replacing the Hadlock method by the INTERGROWTH-21st method may lead to less effective screening for extremes of birthweight percentile.

International versus national growth charts for identifying small and large-for-gestational age newborns: A population-based study in 15 European countries

“…In our observational study of birthweight, we can only measure the differences between international and national newborn charts for identifying births facing higher risks of perinatal mortality. However, our study is in line with research on charts of ultrasound measures (in particular, abdominal circumference) or estimated fetal weight, showing a lower proportion of fetuses with growth parameters under the tenth percentile as well as lower sensitivity of the Intergrowth 21st charts for identifying growth restricted fetuses during pregnancy compared to local or customised charts [47] , [48] , [49] . The population used to build the Intergrowth 21st charts are the same for the fetal and the newborn charts, and therefore concerns about this reference population apply more broadly.…”

Slowing of fetal growth and elevated maternal serum sFLT1:PlGF are associated with early term spontaneous labor

“…Surprisingly, the Texan (Hadlock) methods performed better than the IG21. 29 Most of the women in the Texan study were close to birth (<2 days), whereas the IG21 included women within 2 weeks of birth. As the fetus could gain weight in the 2 weeks between the scan and delivery, the IG21 study corrected the EFW for the duration of the interval using the GA-related changes in EFW in the whole population.…”

Swedish intrauterine growth reference ranges for estimated fetal weight

“…In this study, we used Hadlock et al’s third formula for EFW, which includes the biometric measurements BPD, HC, AC and FL. The formula for EFW was chosen based on compelling evidence from repeated studies which have proven Hadlock et al’s formulae to be superior or non-inferior to a variety of frequently used or more recently developed EFW formulae 15 – 18 , 39 , 40 . In Sweden, the formula adapted by Persson and Weldner in 1986 is recommended by the Swedish Society of Obstetrics and Gynecology and commonly used for estimation of fetal weight 30 , 41 .…”