Birth Weight Curves Research Articles

Birth weight for gestational age: A reference study in a tertiary referral hospital in the middle region of Turkey

BackgroundThe purpose of this study was to establish a fetal birth weight curve for gestational age for patients who presented to our tertiary referral hospital. The curve can be used for epidemiological analysis and also to develop Turkey's first national nomogram. MethodsA total of 68,255 live singleton pregnancies delivered during the study period in a tertiary referral hospital were initially reviewed in this study. The data were carefully collected from hospital records and patients' files. Gestational age (weeks) was assessed by either ultrasound examination or according to the patient's last menstrual period, or both. Sex-specific reference tables for fetal birth weight by gestational age were created, and statistical analyses were carried out for descriptive variables using SPSS 15.0 for Windows. ResultsMost newborns weighed between 3000 g and 4000 g. The percentile fetal birth weight curves for gestational age showed that fetal birth weight increased with the increase in gestational age. Typically, male infants were noted to have higher birth weights than female infants. When our results were compared with those of previous studies, it was demonstrated that values for the 10th percentile were higher in our study, whereas values for the 90th percentile were similar to those of previous studies. ConclusionTo the best of our knowledge, this is the first study evaluating the correlation between gestational age and fetal birth weight with such a large sample size in Turkey. Therefore, the results of this reference study can be helpful in defining normal and abnormal fetal growth in Turkish newborns.

Application of Customized Birth Weight Curves in the Assessment of Perinatal Outcomes in Infants of Diabetic Mothers

Objective: To determine whether the use of customized curves (CC) allows better detection of large- (LGA) or small-for-gestational age (SGA) infants at risk of adverse perinatal morbidity than non-CC in women with diabetes mellitus (DM). Material and Methods: A model of CC was applied to all infants of diabetic mothers (IDM) who attended the Hospital Universitario Materno Infantil de Canarias between 2008 and 2011. We compared perinatal outcomes of IDM classified as LGA or SGA by non-CC versus CC. Results: One of 4 LGA was appropriate for gestational age (AGA) by CC (false-positive rate: 25%) and 30% of SGA by CC were not identified by non-CC (false-negative rate). False-positive LGA and SGA showed similar perinatal outcomes to AGA infants. The rates of cesarean section, cephalopelvic disproportion, total fetal distress and shoulder dystocia were significantly higher in false-negative LGA than in AGA by CC (p < 0.004, p < 0.02, p < 0.04 and p < 0.04, respectively). Fetal distress was higher in false-negative SGA than in AGA by CC (p < 0.03). Discussion: In pregnancies complicated by DM, the use of CC allowed more accurate identification of LGA and SGA infants at high risk of perinatal morbidity than non-CC.

A revised birth weight reference for the United States.

To generate birth weight curves based on the obstetric estimate of gestational age as specified in the revised 2003 U.S. birth certificate. Using National Center for Health Statistics data from 2011, we constructed birth weight curves for neonates between 24 and 42 weeks of gestation. Curves were developed using the obstetric estimate of gestational age that is included in the revised 2003 U.S. birth certificate, which, when available, incorporates ultrasound dating information. Live-born singleton neonates between 500 and 6,000 g without malformations were included. These curves were compared with curves we generated using 1991 data on which the current national reference of Alexander and colleagues is based, a reference that used only last menstrual period to establish gestational age. The 1991 curves were based on 3,684,778 U.S. live births and the 2011 on 3,252,011 births. Birth weight percentile values were greater from 28 to 36 weeks of gestation in the 1991 data set. That is, the birth weights for preterm neonates were overestimated when 1991 reference curves were used compared with the proposed 2011 reference. For example, in 1991, a birth weight of 2,000 g was at the 50th percentile between 31 and 32 weeks of gestation, whereas in 2011, a birth weight of 2,000 g now corresponds to the 50th percentile between 33 and 34 weeks of gestation. Our revised reference curve for the United States provides an updated national reference for birth weight. : II.

Use of Customized Birth Weight Percentiles for the Prediction of Shoulder Dystocia

INTRODUCTION: To investigate the use of customized birth weight percentiles as a predictor for shoulder dystocia. METHODS: Over a 3-year period, shoulder dystocia occurred among 99 of 11,493 deliveries, for an incidence of 0.9%. To conduct a case–control study, 386 deliveries with no shoulder dystocia were randomly selected. Customized birth weight percentile was determined for each woman using Gestation Related Optimal Weight software, which accounts for maternal height, weight, ethnicity, parity, gestational age, and neonate sex. The relationship between customized birth weight percentile and shoulder dystocia was examined using logistic regression and receiver operating characteristic (ROC) curve analysis. RESULTS: The area under the ROC curve for customized birth weight percentile was 0.84 (95% confidence interval [CI] 0.80–0.88), indicating moderate performance of customized birth weight percentile as a risk discriminator. The 70th percentile had the highest sensitivity (79%) and specificity (76%) for prediction of shoulder dystocia (positive likelihood ratio 3.3, negative likelihood ratio 3.6). The area under the ROC curve for birth weight) alone was also 0.84 (95% CI 0.79–0.88). The average birth weight was 3,983 g (standard deviation 516) for those in the case group and 3,320 (standard deviation 435) for those in the control group (P<.001). Most cases of shoulder dystocia (85%) occurred at a birth weight of less than 4,500 g and only three (0.03%) would have been offered prophylactic cesarean delivery based on American College of Obstetricians and Gynecologists recommendations. CONCLUSIONS: Customized birth weight percentile is not an accurate predictor of shoulder dystocia and performs no better than birth weight alone. Continued efforts to identify patients at high risk for shoulder dystocia are needed among those with weights lower than that used to offer prophylactic cesarean delivery by American College of Obstetricians and Gynecologists recommendations.

Should We Use Customized Fetal Growth Percentiles in Urban Canada?

An increasingly common challenge in antenatal care of the small for gestational age (SGA) fetus is the distinction between the constitutionally (physiologically) small fetus and the fetus affected by pathological intrauterine growth restriction (IUGR). We discuss here the rationale and the evidence for the use of customized growth percentiles for the purpose of distinguishing between the fetus with true IUGR and the fetus with constitutional SGA. We also provide estimates of the potential effects of adopting ethnicity-specific birth weight curves on the rates of SGA and large for gestational age status in multi-ethnic metropolitan cities in North America and Europe, such as the City of Toronto. Using customized growth percentiles would result in a considerable decline in the rate of a false-positive diagnosis of SGA among visible minorities, and improve the detection rate of true large for gestational age fetuses among these groups.

References of birth weights for gestational age and sex from a large cohort of singleton births in cameroon.

Objective. To establish the percentile charts of birth weights for gestational age and sex within the Cameroonian population. Methods. A review of medical records of infants born between January 2007 and December 2011 at the maternities of two hospitals in Cameroon, Central Africa. Multiple pregnancies, births of HIV infected women, stillbirths, and births with major fetal malformations were excluded. The smooth curves of birth weight for gestational age and sex were created using the Gamlss package under R.3.0.1 software. Results. The birth weights of 12837 live birth singleton infants born to HIV negative women between 28 and 42 weeks of gestation were analyzed to construct the birth weight curves for gestational age and sex. The smoothed percentile curves of birth weights for gestational age and sex of Cameroonian infants have demonstrated an increasing slope until 40 weeks and then a plateau. There was a varied difference of distribution in birth weights for gestational age between Cameroonian, Botswanan, American, and French infants. Conclusion. We established the reference curves of birth weights for gestational age and sex for Cameroonians. The difference in birth weight curves noted between Cameroonian, Botswanan, American, and French infants suggests the importance of establishing the regional birth weight norms.

New Korean reference for birth weight by gestational age and sex: data from the Korean Statistical Information Service (2008-2012).

PurposeTo construct new Korean reference curves for birth weight by sex and gestational age using contemporary Korean birth weight data and to compare them with the Lubchenco and the 2010 United States (US) intrauterine growth curves.MethodsData of 2,336,727 newborns by the Korean Statistical Information Service (2008-2012) were used. Smoothed percentile curves were created by the Lambda Mu Sigma method using subsample of singleton. The new Korean reference curves were compared with the Lubchenco and the 2010 US intrauterine growth curves.ResultsReference of the 3rd, 10th, 25th, 50th, 75th, 90th, and 97th percentiles birth weight by gestational age were made using 2,249,804 (male, 1,159,070) singleton newborns with gestational age 23-43 weeks. Separate birth weight curves were constructed for male and female. The Korean reference curves are similar to the 2010 US intrauterine growth curves. However, the cutoff values for small for gestational age (<10th percentile) of the new Korean curves differed from those of the Lubchenco curves for each gestational age. The Lubchenco curves underestimated the percentage of infants who were born small for gestational age.ConclusionThe new Korean reference curves for birth weight show a different pattern from the Lubchenco curves, which were made from white neonates more than 60 years ago. Further research on short-term and long-term health outcomes of small for gestational age babies based on the new Korean reference data is needed.

521: Gestational age specific birth-weight curve for Asian Indian newborns

521: Gestational age specific birth-weight curve for Asian Indian newborns

Customized weight curves for Spanish fetuses and newborns

Objectives: To construct a model of customized birthweight curves for use in a Spanish population.Materials and methods: Data of 20 331 newborns were used to construct a customized birthweight model. Multiple regression analysis was performed with newborn weight as the dependent variable and gestational age (GA), sex and maternal (M) weight, height, parity and ethnic origin as the independent variables. Using the new model, 27 507 newborns were classified as adequate for GA (AGA), large for GA (LGA) or small for GA (SGA). The results were compared with those of other customized and non-customized models.Results: The resulting formula for the calculation of optimal neonatal weight was:Optimum weight (g) = 3289.681 + 135.413*GA40–14.063*GA402–0.838*GA403 + 113.889 (if multiparous) + 165.560 (if origin = Asia) + 161.550 (South America) + 67.927 (rest of Europe) +109.265 (North Africa) + 9.392*Maternal-Height + 4.856*Maternal-Weight–0.098*Maternal-Weight2 + 0.001*Maternal-Weight3 + 67.188*Sex + GA40*(6.890*Sex + 9.032 (If multiparous) +0.006*Maternal-Height3 + 0.260*Maternal-Weight) + GA402 (−0.378*Maternal-Height – 0.008*Maternal-Height2) + GA403 (−0.032*Maternal-Height).Weight percentiles were obtained from standard data using optimum weight variation coefficient. Agreement between our customized model and other Spanish models was “good” (κ = 0.717 and κ = 0.736; p < 0.001).Conclusions: Our model is comparable to other Spanish models, but offers the advantage of being customized, updated and freely available on the web. The 30.6% of infants classified as SGA using our model would be considered as AGA following a non-customized model.

Customized growth curves for identification of large‐for‐gestational age neonates in pre‐eclamptic women

To compare the role of two nomograms to classify large-for-gestational age (LGA) neonates in women with pre-eclampsia and to determine the frequency of placental vascular lesions according to the timing of delivery. This cohort study included 118 consecutive women with pre-eclampsia delivering between 23 and 41 weeks’ gestation. The frequencies of LGA neonates according to customized growth curves and a national birth weight (BW) chart were compared. Similarly, the frequencies of LGA neonates and histological placental vascular lesions were compared between pre-eclamptic women delivering at <34 weeks (n=40) and those delivering later (n=78). Customized growth curves allowed classification of a higher proportion of LGA neonates than did BW curves (18.6% (22/118) vs 10.2% (12/118); P=0.002). Among pre-eclamptic women delivering at ≥34 weeks, but not earlier, the proportion of neonates classified as LGA by customized growth curves was higher than that classified by BW curves (26.9% (21/78) vs 15.4% (12/78); P=0.004). Placental vascular lesions were less frequent in pre-eclamptic women delivering at ≥34 weeks than in those delivering earlier (41% (32/78) vs 62.5% (25/40); P=0.03). Customized growth curves allow classification of a higher proportion of LGA neonates than do population birth weight curves among women with pre-eclampsia delivering at ≥34 weeks. Pre-eclamptic women delivering at ≥34 weeks have fewer placental vascular lesions than do those delivering earlier.

New Reference Curves for Head Circumference at Birth, by Gestational Age

The measurement of head circumference (HC) at birth reflects intrauterine brain development. HC charts currently used in Canada are either dated, mixed-gender, nonrepresentative of lower gestational ages (GAs), or reflective of other populations. To create both birth weight and HC curves, we combined weight and HC data from the Canadian Neonatal Network (CNN) database (admissions in NICUs across Canada) with McGill's Obstetrical Neonatal Database (MOND; all births at a tertiary hospital in Montreal, Canada). We included CNN data for GAs of 23 to 34 weeks (2003-2007) and MOND data for GAs of 35 to 41 weeks (1995-2006). Nonsingletons, congenital anomalies, and measurements greater than ±4 SD from the mean were excluded. Distributions of birth weight and HC at each GA were statistically (penalized spline regression) smoothed. Birth weight curves were compared with recent Canadian reference curves and HC curves with historical and/or frequently used curves. We included 39,896 births (3121 births at <30 weeks' GA) to generate the curves. Current weight curves were similar to Canadian reference charts for both genders. Weight and HC measurements in boys were higher than in girls. When classified according to recent international references, the proportion of CNN-MOND infants at ≥32 weeks' GA with HCs <10th percentile was significantly underestimated. When classified according to historical reference curves, a significant number of CNN-MOND infants of all GAs with HCs <10th and >90th percentiles were misclassified. We developed recent gender-specific reference curves for HC at birth for singletons at 23 to 41 completed weeks' GA, which included a large number of very premature infants, reflecting the current geotemporal Canadian population.

Differences in Birthweight Curves Between Newborns of Immigrant Mothers vs. Infants Born in Their Corresponding Native Countries: Systematic Overview

Newborn weight may vary between ethnic groups, but it is not known if birthweight differences exist between term babies born to immigrant mothers compared with those born in their corresponding native countries. We completed a systematic review of all birthweight curves published between 1980 and 2012, based on at least 100 singleton deliveries. We compared the 10th, 50th and 90th percentile birthweight values at 40 weeks gestation for male and female infants born in their native country vs. those infants born to mothers who had emigrated from their native country to Ontario, Canada. For the 50th percentile values, we also calculated a standardised pooled weighted difference and 95% confidence interval [CI] for both sexes. We also assessed whether birthweight differed over time, or if the differences varied by the Human Development Index (HDI) value for the native country. A total of 31 studies from 21 different countries met the inclusion criteria, comprising 13 317 578 males and 12 859 119 females born at 40 weeks gestation. There was a small non-significant rise in reported birthweight percentile values between 1983 and 2006. Nearly all infants born to women in their native country had lower birthweights than those born to mothers who had emigrated from the same country to Canada at the 10th, 50th and 90th percentiles. Overall, the 50th percentile weights differed by 115 g [95% CI 74, 156] for males and 122 g [95% CI 95, 150] for females. As HDI or median birthweight increased, birthweight differences were less pronounced, but not significantly so. Term birthweight percentiles are typically higher among term infants born to mother who immigrate to Canada than those of infants born in their respective native country.

299: Stillbirth prediction and small for gestational age: comparison of a gender specific versus a non-gender specific growth curve

299 Stillbirth prediction and small for gestational age: omparison of a gender specific versus a non-gender pecific growth curve Amanda Trudell, Methodius Tuuli, Ailson Cahill, eorge Macones, Anthony Odibo Washington University in St. Louis, Obstetrics and Gynecology, t. Louis, MO OBJECTIVE: To determine if the use of gender specific growth curves or the diagnosis of small for gestational age (SGA) will improve preiction of stillbirth. STUDY DESIGN: We performed a retrospective cohort study of singleton pregnancies undergoing routine second trimester anatomy ultrasound from 1990-2009. Pregnancies complicated by major structural fetal anomalies, fetal aneuploidy, incomplete birthweight information and undocumented fetal gender were excluded. SGA was defined as birthweight 10th percentile as determined by a gender-specific growth curve and a standard growth curve (Alexander et al. 1996). We assessed the association between SGA and stillbirth (defined as fetal death 20 weeks) using these two birthweight curves. Logistic regression was used to control for maternal age, nulliparity, race, BMI, smoking, CHTN, and pre-gestational diabetes. The test characteristics for each curve and the odds ratio (OR) and 95% CI for the association between SGA and stillbirth were evaluated. Receiver operating characteristic curves (ROC) for each growth curve and the area under the curve (AUC) were compared using non-parametric statistics. RESULTS: Among 57,170 pregnancies meeting inclusion criteria, 319 0.6%) pregnancies were complicated by stillbirth. SGA as defined by he gender specific growth curve was a better predictor of stillbirth ompared to the standard growth curve (adjusted OR 19.6 [95% CI 5.3-25.1] vs. 5.26 [95% CI 4.1-6.7]), respectively. Sensitivity and pecificity for SGA by the gender specific growth curve and standard rowth curve were 63.9% and 92%, and 32% and 92.8%, respectively. he AUC for the gender specific growth curve was greater than the UC for the standard growth curve (0.83 vs. 0.72 P 0.001). CONCLUSION: Our findings suggest the adoption of gender-specific charts for growth evaluation as they are more discriminatory in identifying growth-restricted fetuses at risk for stillbirth.

One Size Does Not Fit All: Differences in Newborn Weight Among Mothers of Philippine and Other East Asian Origin

ObjectiveTo determine the likelihood that infants born to Filipina, other East Asian, and Canadian-born women may be misclassified as small for gestational age when using conventional Canadian birth weight curves rather than those specific to their world region. MethodsWe conducted a population-based study of 548 418 singleton live births in Ontario between 2002 and 2007. Smoothed birth weight percentile curves were generated for males and females born to women from Canada, the Philippines, and the rest of East Asia/Pacific. We determined the likelihood of misclassifying an infant as small for gestational age (SGA < 10th percentile weight) or large for gestational age (LGA ≥ 90th percentile weight) on a Canadian-born birth weight curve vs. a curve specific to the other two world regions. ResultsFor gestation-specific 10th and 50th percentiles, term infants born to women from the Philippines often had significantly lower birth weights than infants of Canadian-born mothers. Controlling for maternal age and parity, approximately 88 per 1000 male newborns (95% CI 82 to 95) and 72 per 1000 female newborns (95% CI 54 to 60) of mothers from the Philippines were at risk of being misclassified as SGA. LGA would be missed in approximately 54 per 1000 male newborns (95% CI 49 to 59) and 49 per 1000 female newborns (95% CI 44 to 54) of Filipina mothers. Misclassification of both SGA and LGA was more pronounced among infants of Filipina mothers than of mothers from other East Asian origin. ConclusionsInfants of mothers born in the Philippines weigh significantly less than those of Canadian-born women or mothers emigrating from other East Asian countries. Those who use birth weight curves should consider these differences.

The effect of customized growth charts on the identification of large for gestational age newborns

Objective: To determine the effect of using customized vs. standard population birthweight curves to define large for gestational age (LGA) infants. Methods: We analyzed data obtained from 2,097 singleton pregnancies using three different methods of classifying newborn birthweight: standard population curves, British or Spanish customized curves. We recorded maternal characteristics, proportion of LGA newborns when using each method, percentage of LGA according to one method but not for the others, and concordance between the different methods. Results: The proportion of LGA newborns according to Spanish customized curves was significantly lower than that calculated using either standard general population birthweight curves or British curves (p < 0.001). A third (33.9%) of the infants classified as LGA according to the general population method were adequate for gestational age (AGA) when the Spanish customized curves were used, and 18.5% of non-LGA were LGA according to customized curves (p < 0.001). Concordance between the different models high, but on excluding AGA the concordance coefficient was low (Cohen’s κ <0.4). Conclusions: The use of customized curves allows differentiation between constitutional LGA and cases of fetal overgrowth, leading to a decrease in the rate of both false-positives and negatives as well as the overall proportion of LGA babies.

Birth weight- and fetal weight-growth restriction: Impact on neurodevelopment

BackgroundThe newborn classified as growth-restricted on fetal weight curves, but not on birth weight curves, is classified prenatally as small for gestational age (SGA), but postnatally as appropriate for gestational age (AGA). AimsTo see (1) to what extent the neurodevelopmental outcomes at 24months corrected age differed among three groups of infants (those identified as SGA based on birth weight curves (B-SGA), those identified as SGA based on fetal weight curves only (F-SGA), and the referent group of infants considered AGA, (2) if girls and boys were equally affected by growth restriction, and (3) to what extent neurosensory limitations influenced what we found. Study designObservational cohort of births before the 28th week of gestation. Outcome measures: Mental Development Index (MDI) and Psychomotor Development Index (PDI) of the Bayley Scales of Infant Development II. ResultsB-SGA, but not F-SGA girls were at an increased risk of a PDI<70 (OR=2.8; 95% CI: 1.5, 5.3) compared to AGA girls. B-SGA and F-SGA boys were not at greater risk of low developmental indices than AGA boys. Neurosensory limitations diminished associations among girls of B-SGA with low MDI, and among boys B-SGA and F-SGA with PDI<70. ConclusionsOnly girls with the most severe growth restriction were at increased risk of neurodevelopmental impairment at 24months corrected age in the total sample. Neurosensory limitations appear to interfere with assessing growth restriction effects in both girls and boys born preterm.

Intrauterine growth characteristics of twins and those twins discordant birthweight

To investigate the intrauterine growth characteristics of twins and birthweight discordant twins (discordant twins). Total of 1010 twin pregnancies (2020 fetuses) with complete delivery records from the Department of Obstetrics and Gynecology, the First and Third Affiliated Hospital of SUN Yat-sen University between January 1, 2000 and July 31, 2010 were studied retrospectively. One handred and ninteen cases (238 fetuses) with intrapair birthweight difference ≥ 25% were determined as the discordant twins group, and the other 891 cases (1782 fetuses) with intrapair birthweight difference < 25% were identified as the concordant twins group. The singleton control group included 4042 singleton pregnancies in the same period. (1) Comparison of clinical data between the twins groups: the birthweight of larger-twin, smaller-twin and intrapair birthweight difference in the discordant twins group and the concordant twins group were (2090 ± 827) g, (1392 ± 592) g, (33.9 ± 9.3)%, and (2408 ± 543) g, (2191 ± 505) g, (8.9 ± 6.5)%, respectively, with significant differences (P < 0.01). The incidence of discordant twins was 11.78% (119/1010). Compared with the concordant twins group, the discordant twins group had higher proportion of monochorionic twins, and higher prevalence of pregnancy complications such as late miscarriage, abnormal umbilical insertion, twin-twin transfusion syndrome and hypertensive disorders in pregnancy (P < 0.05). (2) The characteristics of twin birthweight distribution: 1) In all the 2020 twins, 80.05% (1617/2020) fetuses had birthweight below the 50(th) percentile of the singleton control group, while 23.71% (479/2020) feeuses got birthweight below the 10(th) percentile of the singleton control group. 2) After 19(th) gestational week, the 50(th) and 90(th) percentile of all twins' birthweight were lower than those of singletons. After 38(th) gestational week, the birthweight of singletons kept increasing and reached its peak at 41(th) week, while the birthweight of twins reached its peak at 38(th) week, followed by a decline at 39 weeks, which was even lower than the 10(th) percentile of the singleton control group. 3) The distribution of birthweight of larger- and smaller-twin in the discordant twins group: 65 (54.6%, 65/119) larger-twins and one (0.8%, 1/119) smaller-twin had birthweight above the 50(th) percentile of all twins, while 5 (4.2%, 5/119) larger-twins and 97 (81.5%, 97/119) smaller-twins got birthweight below the 10(th) percentile of all twins. (1) The patterns of birthweight curves for each gestational week are different between twins and singletons. In order to evaluate the growth of twins, birthweight reference for twins should be employed. (2) According to the reference of twins birthweight, the most discordant twins are complicated with fetal growth restriction at least in one twin.

Birth Weight Curves Tailored to Maternal World Region

BackgroundNewborns of certain immigrant mothers are smaller at birth than those of domestically born mothers. Contemporary, population-derived percentile curves for these newborns are lacking, as are estimates of their risk of being misclassified as too small or too large using conventional rather than tailored birth weight curves. MethodsWe completed a population-based study of 766 688 singleton live births in Ontario from 2002 to 2007. Smoothed birth weight percentile curves were generated for males and females, categorized by maternal world region of birth: Canada (63.5%), Europe/Western nations (7.6%), Africa/Caribbean (4.9%), Middle East/North Africa (3.4%), Latin America (3.4%), East Asia/Pacific (8.1%), and South Asia (9.2%). We determined the likelihood of misclassifying an infant as small for gestational age (≤ 10th percentile for weight) or as large for gestational age (≥ 90th percentile for weight) on a Canadian-born maternal curve versus one specific to maternal world region of origin. ResultsSignificantly lower birth weights were seen at gestationspecific 10th, 50th, and 90th percentiles among term infants born to mothers from each world region, with the exception of Europe/Western nations, compared with those for infants of Canadian-born mothers. For example, for South Asian babies born at 40 weeks’ gestation, the absolute difference at the 10th percentile was 198g (95% CI 183 to 212) for males and 170g (95% CI 161 to 179) for females. Controlling for maternal age and parity, South Asian males had an odds ratio of 2.60 (95% CI 2.53 to 2.68) of being misclassified as small for gestational age, equivalent to approximately 116 in 1000 newborns; for South Asian females the OR was 2.41 (95% CI 2.34 to 2.48), equivalent to approximately 106 per 1000 newborns. Large for gestational age would be missed in approximately 61 per 1000 male and 57 per 1000 female South Asian newborns if conventional rather than ethnicity-specific birth weight curves were used. ConclusionsBirth weight curves need to be modified for newborns of immigrant mothers originating from non-European/Western nations.

Reference birthweights for the Argentine population by multiplicity of birth, sex, and gestational age

To develop new and improved reference birthweights for the Argentine population as a whole with a breakdown by gestational age (GA), sex and multiplicity of birth. The population studied included all live births resulting from single (n = 3,478,286) and double (n = 57,654) births in Argentina during the period 2003- 2007. The probable errors in classifying GA on the basis of last menstruation were corrected using normal mixture models. The percentiles were obtained by quantile regression, which also made it possible to smooth out the curves. Birthweight curves for single births were obtained between weeks 22 and 43 of gestation, and curves for double births between weeks 24 and 41, with a breakdown by the sex of the neonate. Compared with those of previous studies, these reference birthweights do not overestimate the proportion of live births large for their GA. An increase in birthweight was also observed during the period of study. The proposed curves have the advantages of being based on large numbers, of being representative of the most recent Argentine births, of distinguishing the number of births and the sex of the neonates, and of minimizing GA classification errors. They are therefore a useful tool for measuring inequalities and thus identifying population groups at higher risk of adverse perinatal events.

Evaluation of modified retinopathy of prematurity screening guidelines using birth weight as the sole inclusion criterion

Purpose:The purpose was to determine if birth weight (BW) alone can be the sole criterion for screening infants at risk for retinopathy of prematurity (ROP).Materials and Methods:In this retrospective, observational case series, 208 infants were screened for ROP using the American Association for Pediatric Ophthalmology and Strabismus (AAPOS) Guidelines (1997). Variables examined included gestational age (GA), birth weight (BW), and a composite variable BWGA Index [(grams × weeks)/1000], which takes into consideration both the birth weight and gestational age of the infant. Infants were divided into two groups: Group 1, BW ≤1250 g, and Group 2, BW >1250 g. Multivariate analysis was performed to detect factors predictive of ROP. Receiver operator characteristic (ROC) curves were generated to determine the efficacy of screening using the BW, GA, and BWGA Index. Statistical analyses were performed with logistic regression with a P-value of 0.05 or less indicating statistical significance.Results:Varying stages of ROP were present in 116 of 416 eyes. Of the 105 eyes in Group 2, only 1 eye developed stage 1 ROP. Only Group 1 eyes developed stage 3 or higher ROP. The ROC curve for BW alone gave an area under the curve (AUC) of 0.797 (standard error [SE] = 0.0329, P < 0.0001); for GA, AUC was 0.801 (SE = 0.0340, P < 0.0001) and for the BWGA Index, the AUC was 0.808 (SE = 0.0324, P < 0.0001). Using 1250-g BW as a criterion for ROP screening would have decreased the number of screenings by 24%, and did not exclude any ROP higher than stage 1.Conclusion:Data from our neonatal intensive care unit suggest that birth weight ≤ 1250 g alone is an adequate parameter to identify premature infants at risk for ROP.