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New birth weight reference standards customised to birth order and sex of babies from South India.
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MedLine Citation:
PMID:  23409828     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
BACKGROUND: The foetal growth standards for Indian children which are available today suffer due to methodological problems. These are, for example, not adhering to the WHO recommendation to base gestational age on the number of completed weeks and secondly, not excluding mothers with risk factors. This study has addressed both the above issues and in addition provides birthweight reference ranges with regard to sex of the baby and maternal parity.
METHODS: Data from the labour room register from 1996 to 2010 was obtained. A rotational sampling scheme was used i.e. the 12 months of the year were divided into 4 quadrants. All deliveries in January were considered to represent the first quadrant. Similarly all deliveries in April, July and October were considered to represent 2nd, 3rd and 4th quadrants. In each successive year different months were included in each quadrant. Only those mothers aged 20-39 years and delivered between 24 to 42 weeks gestational age were considered. Those mothers with obstetric risk factors were excluded. The reference standards were fitted using the Generalized Additive Models for Location Scale and Shape (GAMLSS) method for Box-Cox t distribution with cubic spline smoothing.
RESULTS: There were 41,055 deliveries considered. When women with risk factors were excluded 19,501 deliveries could be included in the final analysis. The male babies of term firstborn were found to be 45 g heavier than female babies. The mean birthweights were 2934 g and 2889.5 g respectively. Similarly, among the preterm babies, the first born male babies weighed 152 g more than the female babies. The mean birthweights were 1996 g and 1844 g respectively.In the case of later born babies, the term male babies weighed 116 grams more than the females. The mean birth weights were 3085 grams and 2969 grams respectively. When considering later born preterm babies, the males outweighed the female babies by 111 grams. The mean birthweights were 2089 grams and 1978 grams respectively. There was a substantial agreement range from k=.883, (p<.01) to k=.943, (p<.01) between adjusted and unadjusted percentile classification for the subgroups of male and female babies and first born and later born ones.Birth weight charts were adjusted for maternal height using regression methods. The birth weight charts for the first born and later born babies were regrouped into 4 categories, including male and female sexes of the babies. Reference ranges were acquired both for term and preterm babies.With economic reforms, one expects improvement in birthweights. The mean (sd) birthweights of the year 1996 was 2846 (562) as compared to year 2010 (15 years later) which was 2907 (571). There was only a difference of 61 grams in the mean birthweights over one and a half decade.
CONCLUSION: New standards are presented from a large number of deliveries over 15 years, customised to the maternal height, from a south Indian tertiary hospital. Reference ranges are made available separately for first born or later born babies, for male and female sexes and for term and preterm babies.
Authors:
Velusamy Saravana Kumar; Lakshmanan Jeyaseelan; Tunny Sebastian; Annie Regi; Jiji Mathew; Ruby Jose
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Publication Detail:
Type:  Journal Article     Date:  2013-02-14
Journal Detail:
Title:  BMC pregnancy and childbirth     Volume:  13     ISSN:  1471-2393     ISO Abbreviation:  BMC Pregnancy Childbirth     Publication Date:  2013  
Date Detail:
Created Date:  2013-02-27     Completed Date:  2013-07-05     Revised Date:  2013-07-11    
Medline Journal Info:
Nlm Unique ID:  100967799     Medline TA:  BMC Pregnancy Childbirth     Country:  England    
Other Details:
Languages:  eng     Pagination:  38     Citation Subset:  IM    
Affiliation:
Department of Biostatistics, Christian Medical College and Hospital, Vellore 632004, India.
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MeSH Terms
Descriptor/Qualifier:
Adult
Birth Order*
Birth Weight / physiology*
Body Height / physiology
Female
Gestational Age
Humans
India
Infant, Newborn
Infant, Premature / physiology
Logistic Models
Male
Parity
Reference Values
Sex Factors
Comments/Corrections

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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Journal Information
Journal ID (nlm-ta): BMC Pregnancy Childbirth
Journal ID (iso-abbrev): BMC Pregnancy Childbirth
ISSN: 1471-2393
Publisher: BioMed Central
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Copyright ©2013 Kumar et al; licensee BioMed Central Ltd.
open-access:
Received Day: 11 Month: 5 Year: 2012
Accepted Day: 12 Month: 2 Year: 2013
collection publication date: Year: 2013
Electronic publication date: Day: 14 Month: 2 Year: 2013
Volume: 13First Page: 38 Last Page: 38
PubMed Id: 23409828
ID: 3583685
Publisher Id: 1471-2393-13-38
DOI: 10.1186/1471-2393-13-38

New birth weight reference standards customised to birth order and sex of babies from South India
Velusamy Saravana Kumar1 Email: saravanan.biostat1985@gmail.com
Lakshmanan Jeyaseelan1 Email: ljey@cmcvellore.ac.in
Tunny Sebastian1 Email: tuna957@gmail.com
Annie Regi2 Email: annieregi@cmcvellore.ac.in
Jiji Mathew2 Email: jiji_mathew@yahoo.co.in
Ruby Jose2 Email: rubyjose1@gmail.com
1Department of Biostatistics, Christian Medical College and Hospital, Vellore, 632004, India
2Department of Obstetrics and Gynaecology, Christian Medical College and Hospital, Vellore, 632004, India

Background

Investigators and researchers have used the reference standards which were developed globally due to lack of availability of population or country specific standards. A decline in the use of these standards has been reported [1] as regionally developed standards are made available [2-5]. Mohan et al. (1990) have reported growth curves for North Indian babies from a referral hospital [1]. However, these reference standards have limitations as they failed to exclude mothers and babies with risk factors and the hospital predominantly served mothers with low socioeconomic status. Most of the above studies have not adhered to the World Health Organization (WHO) recommendation to base gestational age on number of completed weeks. The latest report on birth weight standards for South Indian babies was published in 1996, which is nearly one and a half decades old and may no longer be pertinent to infants born in more recent years [2]. The country has gone through economic revolution in the last two decades, which has influenced all sections of society. Therefore, the birth weight of the new born babies is expected to increase. Kramer et al. have reported the validity of the calculation of gestational age from the last menstrual period and therefore the credibility of the birth weight standards which were published earlier [3-6]. The gestational age from 24 weeks to 29 weeks are expected to be small in numbers and therefore likely to have a skewed distribution in birth weight. Some studies have failed to smooth the standard curves using appropriate distribution such as log normal or Box – Cox t distribution with cubic spline smoothing [7,8]. In this study we have overcome the above mentioned limitations by studying children born from 1996 to 2010 in a referral hospital which has a unique medical records system, with appropriate inclusion criteria, foetal sex and mother’s gravidity and gestation specific growth standards for Indian children.


Methods

The Christian Medical College and Hospital is a referral hospital in South India, which caters to 47,110 outpatients and 15,662 inpatients per year. The department of Obstetrics and Gynaecology on an average delivered 20 babies per day in 1996 and 40 babies per day in 2010. The data was obtained from the Labour room register which was maintained by the nursing personnel and supervised by the Head of Obstetrics department. This contains all the information about women who delivered in this institution. Permission was obtained from all the Obstetric departmental Unit Heads. This study was approved by the ethics committee of [IRB Min. No. 7109 dated 10.03.2010] Christian Medical College.

Sampling

The twelve months of the year were divided in to 4 quadrants. In the year 1996, all deliveries which took place in January were considered to represent the first quadrant. In the second quadrant, all deliveries in the month of April were considered. All deliveries in the months of July and October were considered to represent the deliveries in the third and fourth quadrants. In the second year of the study (1997) all deliveries which took place in February, May, August and November were taken to represent the first, second, third and fourth quarter of the year. In the third year of study (1998), all deliveries which took place in March, June, September and December were taken to represent the first, second, third and fourth quarter of the year. The above cycle was repeated for the next 3 years and continued until the year 2010 [9].

Inclusion and exclusion criteria

Mothers aged 20 to 39 years and deliveries of gestational age between 24 weeks to 42 weeks were considered. The mothers, who had hypertensive disorders, gestational diabetes, diabetes mellitus, heart disease, and twin pregnancies, were excluded from the analyses. The gestational age specific birth weights which were above +3SD or below –3SD values were excluded from the analyses. The maternal height was regrouped into tertiles with categories as < 151 cm, 151 – 158 cm and > 158 cm based on the maternal height distribution of the mothers. Linear regression was employed to get the estimate of birthweight in relation to the maternal height. It showed a significant increase in birthweight of 135 grams. These 135 grams were added to the birthweight for shorter women and for taller women 135 grams were subtracted. Women with normal height (151–158 cm) did not have any adjustments in birthweight. These corrections yielded us the birthweights adjusted for maternal height.

The modified birthweights were adjusted with gestational ages to produce the birthweight centiles for each of the four groups in the term as well as the preterm groups. (Male & Female first born, Male & Female later born).

Distribution and smoothing

The birth weights adjusted for maternal height for babies born from gestational age 24 weeks to 30 weeks had skewed distribution to the right side. However, as the number of deliveries increased in the subsequent gestational weeks, the birth weight distribution followed normal distribution. In the modelling we have assumed Box-Cox t distribution in order to get over this skewness. Cubic Spline smoothing has been applied using the Generalized Additive Models for Location Scale and Shape (GAMLSS) method using R software (Stasinopoulos and Rigby 2007) [10]. The GAMLSS models are semi parametric regression type models. However, the response variable needs to follow parametric distribution. The 3rd, 10th, 25th, 50th, 75th, 90th and 97th percentiles and mean and standard deviations were computed using R software. These centiles for birthweight adjusted for maternal height were done separately for firstborn males, females and later born males and females.

Data from the labour room register was entered using EPIINFO software. Completed weeks gestational age was considered for nomograms. The best estimate of gestation based on reliable menstrual history, early antenatal clinical examination and sonographic fetal biometry was used. Birth weights were measured to the nearest 50 g on a Braun electronic weighing scale within one hour of birth.


Results

In total, there were 41,055 deliveries considered. Of these, complete data were available for 25,090 deliveries. When women with risk factors were excluded (mild and severe PIH, Chronic hypertension, GDM, Pregestational diabetics, cardiac disease, twins, teenaged primigravidas and mothers more than 40 years of age), 19,501 deliveries could be included for analyses. Most of the women were in the age group 25 – 29 years 41.7% (8133). Close to this is the 20 to 24 years age group which constituted 40.1% (7817). Mothers more than 30 years constituted only 18.2% (3551).

The maximum number of mothers who delivered belonged to the Hindu religion, and formed 82% (15933). Muslims formed 11.1% (2164), and Christians constituted 6.9% (1343).

Most (91.8%) of the mothers were housewives. Professionals were a minority, 4.3% (844), and mothers trained for skilled work were only 1.4% (241). When considering education of the mothers, 28.6% (4961) were graduates or more highly educated. A small percent was illiterate 5.1% (895). Those who had primary education formed 6.2% (1085) and those with secondary education 13.6% (2367). Those who had high school and higher secondary education constituted 8099 (46.5%) of the mothers.

When sub grouped into 3, based on the heights of the mothers, 24%, 48% and 28% of the mothers fell into the 3 groups ,whose height was <151 cm; 151-158 cm and >158 cm respectively.

There were 2379 firstborn and 17,092 later born. There were 1236 (6.3%) male babies in the first born group and the first born females were 1143 (5.9%) in number. Among the later born babies, male babies were 8739 (44.9%) in number and females 8353 (42.9%).

Term and preterm first born babies

The male babies of term first born mothers were found to be 45 grams heavier than female babies. The mean birthweights were 2934 grams and 2889.5 grams respectively. Similarly, among the preterms, male babies weighed 152 grams more than the female babies. The mean birthweights were 1996 grams and 1844 grams respectively.

Term and preterm later born babies

In the case of later born babies, term male babies weighed 116 grams more than the females. The mean birth weights were 3085 grams and 2969 grams respectively. When considering preterm babies among the later born, the males outweighed the female babies by 111 grams. The mean birthweights were 2089 grams and 1978 grams respectively.

Table 1 shows the 3rd, 10th, 25th, 50th, 75th, 90th, 97th percentile, mean and SD birth weights for male and female babies of primigravidae. Figures 1 and 2 shows the smoothed percentile curves for male and female babies of first born separately. The growth curves for various percentiles are smooth and increasing steadily as gestational age increases.

Table 2 shows the 3rd, 10th, 25th, 50th, 75th, 90th, 97th percentile, mean and SD birth weights for male and female babies of later born babies. Figures 3 and 4 shows the smoothed percentile curves for male and female babies of later born babies separately.

Table 3 presents the agreement between the model (adjusted) and actual data (unadjusted) percentiles for first born and later born male and female babies.

Agreement of centiles for male & female babies among the first born babies

When considering first born male babies, there is significant agreement between adjusted and unadjusted percentile classification (k=.883, p<.001). However, 7% of the male babies in <10th percentile category was misclassified as 10–90th percentile category. Nearly 2% of the babies from 10–90th percentile category was misclassified as <10th and >90th percentile. Nearly 5% of the babies >90th percentile category was misclassified as 10–90th percentile. When considering female babies, there is a significant substantial agreement between the adjusted and unadjusted classifications (k=.897, p<.001). The misclassifications to the next category percentiles rates were the same as in the male babies.

Agreement of centiles for male & female babies within the later born group

There is a significant agreement between adjusted and unadjusted percentile classification (k=.917, p<.01) in later born male babies. However, 5% of the male babies in < 10th percentile category was misclassified as 10–90th percentile category and 1.5% from 10–90th percentile category was misclassified as <10th and >90th percentile category. 2.8% of the >90th percentile category was misclassified as 10–90th percentile category. Similarly, among the later born female babies, there is a significant agreement between adjusted and unadjusted percentile classification (k=.934, p<.01). The misclassifications to the next category percentiles rates were nearly the same as among the male babies.

The mean (sd) of birthweights of the year 1996 was 2846 g (562) as compared to year 2010 (15 years later) which was 2907 (571), there was only a difference of 61 grams in the mean birthweights over one and half decades.


Discussion

This is the biggest study ever from India, dealing with nearly 20,000 deliveries, including normal mothers with no antenatal risk factors from the same hospital covering 15 years. In addition to this, a major advantage is the reliance on early ultrasound-based estimates of gestational ages and appropriate statistical modelling using Box-Cox t distribution to get over the skewness of birth weight distribution and cubic spline smoothing. Therefore, we have established standards for first born and later born mothers for male and female babies separately. Some of the earlier standards have not done these adjustments [1,11] and some of the standards are very old [12,13]. The absence of downturn trend in the curves in the post term period is similar to curves reported [14] and are consistent with evidence based on early ultrasound-based gestational ages [15,16].

This study also compared the unadjusted centiles to adjusted and smoothed centiles. With male babies of first born, 7% of the adjusted <10th percentile was misclassified as 10–90th percentile and nearly each 2% of 10–90th category was misclassified as <10th or >90th percentile category. A similar trend was obtained in female babies of first born and male and female babies of later born babies. Though there is very good agreement in general the highest misclassification rate was nearly 7.5%. Therefore the use of unadjusted percentiles may lead to unnecessary intervention and anxiety for the parents of babies whose weight fall in the range of lower and upper centiles according to adjusted centiles.

The limitation of the study is that the observations are cross-sectional. That is, birth weights of different babies were observed at different gestational ages at delivery. Ideally this has to be longitudinal in nature, that is, the same number of pregnancies and their birth weights have to be observed. Anthropometric measurements during gestation are feasible only using ultra-sound. However, the ultra-sound measurements have not been proved to be valid and reliable [17,18]. Temporal trends toward increasing maternal weight, weight gain during pregnancy due to various socio economic changes that have been taking place in the country in the last one and half decade needs to be studied.

With economic reforms, one expects improvement in birthweights. The mean (sd) of birthweights of the year 1996 was 2846 g (562) as compared to year 2010 (15 years later) which was 2907 (571), there was a difference of only 61 grams in the mean birthweights over one and half decades.


Conclusion

New standards for birth weights of Indian newborns, both term and preterm have been established. In addition, birth weight standards based on the sex of the baby and maternal parity have also been brought out. These new standards will allow interventions to be based on Indian standards.


Consent

Written informed consent was obtained from the patient for publication of this report.


Competing interests

The authors declare that they have no competing interests.


Authors’ contributions

All authors (VS, LJ, TS, AR, JM, RJ) contributed to the design of the study and interpretation of data. (VS, LJ, TS) performed the data analysis. (LJ, RJ) drafted the manuscript. All authors (VS, LJ, TS, AR, JM, RJ) critically revised the manuscript and have approved the final version.


Publishing datasets

The dataset will not be available for publishing online since further research has been planned.


Pre-publication history

The pre-publication history for this paper can be accessed here:

http://www.biomedcentral.com/1471-2393/13/38/prepub


Acknowledgements

I acknowledge Dr. Denny Fleming’s, (Clinical Pharmacologist Christian Medical College Vellore) help in correcting the English of main manuscript.


References
Mohan M,Prasad SR,Chellani HK,Kapani V,Intrauterine growth curves in north Indian babies: weight, length, head circumference and ponderal indexIndian PediatrYear: 19902743512361742
Mathai M,Jacob S,Karthikeyan NG,Birthweight standards for south Indian babiesIndian PediatrYear: 1996332032098772839
Kramer MS,McLean FH,Boyd ME,Usher RH,The Validity of Gestational Age Estimation by Menstrual Dating in Term, Preterm, and Postterm GestationsJAMAYear: 19882603306330810.1001/jama.1988.034102200900343054193
Rj D,Population-based intrauterine growth curves from computerized birth certificatesSouth Med JYear: 198376140110.1097/00007611-198311000-000206635732
Gardosi J,Chang A,Kalyan B,Sahota D,Symonds EM,Customised antenatal growth chartsLancetYear: 199233928328710.1016/0140-6736(92)91342-61346292
Zhang J,Bowes J,Birth-weight-for-gestational-age patterns by race, sex, and parity in the United States populationObstet GynecolYear: 19958620020810.1016/0029-7844(95)00142-E7617350
Arbuckle TE,Wilkins R,Sherman GJ,Birth weight percentiles by gestational age in CanadaObstet GynecolYear: 19938139488416459
Roberts C,Mueller L,Hadler J,Birth-weight percentiles by gestational age, Connecticut 1988–1993Conn MedYear: 1996601318774934
Eckler AR,Rotation samplingAnn Math StatYear: 19552666468510.1214/aoms/1177728427
Stasinopoulos DM,Rigby RA,Generalized additive models for location scale and shape (GAMLSS) in RJ Stat SoftwYear: 200723146
Bhatia BD,Bhargava V,Chatterjee M,Kota VL,Singh LI,Jain NP,Studies on fetal growth patterns: intrauterine growth percentiles for singleton live born babiesIndian PediatrYear: 1981186476537319614
Ghosh S,Bhargava SK,Madhavan S,Taskar AD,Bhargava V,Nigam SK,Intra-uterine growth of North Indian babiesPediatricsYear: 1971478268305573867
Mittal SK,Singh PA,Gupta RC,Intrauterine growth and low birth weight criteria in Punjabi infantsIndian PediatrYear: 1976136796821002261
Kramer MS,Platt RW,Wen SW,Joseph KS,Allen A,Abrahamowicz M,Blondel B,Bréart G,A new and improved population-based Canadian reference for birth weight for gestational agePediatricsYear: 2001108E3510.1542/peds.108.2.e3511483845
McLean FH,Boyd ME,Usher RH,Kramer MS,Postterm infants: too big or too small?Am J Obstet GynecolYear: 19911646196241992713
Wilcox M,Gardosi J,Mongelli M,Ray C,Johnson I,Birth weight from pregnancies dated by ultrasonography in a multicultural British populationBMJYear: 199330758859110.1136/bmj.307.6904.5888401014
Secher NJ,Kern Hansen P,Thomsen BL,Keiding N,Growth retardation in preterm infantsBr J Obstet GynaecolYear: 19879411512010.1111/j.1471-0528.1987.tb02336.x3548805
Hediger ML,Scholl TO,Schall JI,Miller LW,Fischer RL,Fetal growth and the etiology of preterm deliveryObstet GynecolYear: 19958517518210.1016/0029-7844(94)00365-K7824227

Figures

[Figure ID: F1]
Figure 1 

First born male babies smoothed centiles graph for Weight (gms) by gestational age (weeks).



[Figure ID: F2]
Figure 2 

First born female babies smoothed centiles graph for weight (gms) by gestational age (weeks).



[Figure ID: F3]
Figure 3 

Later born male babies smoothed centiles graph for weight (gms) by gestational age (weeks).



[Figure ID: F4]
Figure 4 

Later born female babies smoothed centiles graph for weight (gms) by gestational age (weeks).



Tables
[TableWrap ID: T1] Table 1 

Smoothed percentiles for birth weight (grams) of first born male and female babies


First born male babies smoothed percentiles
First born female babies smoothed percentiles
GA N C3 C10 C25 C50 C75 C90 C97 Mean SD N C3 C10 C25 C50 C75 C90 C97 Mean SD
31
8
590
871
1131
1394
1637
1842
2035
1427
261
6
601
773
953
1159
1369
1562
1755
1146
310
32
13
744
1055
1340
1630
1899
2126
2340
1513
496
8
774
976
1187
1426
1670
1894
2119
1400
395
33
13
939
1262
1558
1861
2142
2381
2606
1820
529
10
961
1186
1421
1687
1958
2207
2456
1733
397
34
23
1164
1482
1777
2079
2362
2604
2833
2112
358
11
1157
1399
1649
1934
2223
2488
2754
2076
422
35
33
1379
1691
1981
2282
2566
2809
3039
2300
450
16
1366
1616
1874
2166
2464
2735
3007
1941
417
36
53
1591
1892
2176
2472
2752
2993
3222
2353
486
43
1598
1847
2104
2393
2688
2957
3225
2410
433
37
124
1806
2092
2365
2652
2925
3160
3385
2687
384
81
1821
2063
2311
2591
2875
3134
3392
2637
424
38
196
1982
2259
2524
2804
3072
3304
3525
2774
429
184
2004
2236
2474
2741
3012
3259
3505
2742
397
39
269
2152
2417
2673
2944
3204
3429
3645
2912
388
265
2142
2370
2604
2866
3132
3374
3615
2856
384
40
308
2287
2547
2798
3065
3321
3544
3758
3083
391
321
2250
2479
2714
2977
3244
3487
3729
2994
404
41
82
2366
2614
2855
3112
3359
3575
3781
3078
383
91
2353
2570
2792
3042
3294
3523
3751
3038
365
42 7 2419 2652 2877 3119 3352 3555 3751 2887 245 11 2448 2647 2851 3079 3310 3520 3728 3005 322

GA = Gestational Age (weeks), N = Number of babies in each group, C3 – C97 = Predicted Smoothed percentiles from GAMLSS model Mean & SD = Arithmetic Mean and standard deviation in each group.


[TableWrap ID: T2] Table 2 

Smoothed percentiles for birth weight (grams) of later born male and female babies


Later born male babies smoothed percentiles
Later born female babies smoothed percentiles
GA N C3 C10 C25 C50 C75 C90 C97 Mean SD N C3 C10 C25 C50 C75 C90 C97 Mean SD
24
11
73
199
392
645
916
1172
1440
663
102
5
55
176
383
679
1018
1353
1714
792
133
25
9
99
259
491
785
1096
1388
1692
1099
645
8
75
226
464
787
1149
1503
1882
1136
833
26
14
131
328
594
920
1260
1578
1907
914
282
9
104
287
552
895
1270
1634
2021
893
490
27
16
175
409
704
1053
1412
1745
2090
1408
909
13
147
365
652
1007
1388
1753
2142
1217
836
28
22
237
508
824
1185
1552
1892
2242
1071
316
18
211
463
766
1126
1506
1869
2253
1208
500
29
14
327
629
958
1324
1691
2031
2381
1141
416
24
302
582
894
1256
1633
1991
2369
1195
480
30
45
450
775
1107
1470
1834
2168
2513
1595
721
41
421
720
1038
1399
1772
2126
2498
1470
695
31
39
610
943
1271
1626
1980
2306
2642
1567
387
51
567
878
1197
1557
1926
2275
2642
1479
451
32
60
795
1127
1449
1795
2140
2457
2785
1820
496
51
735
1052
1373
1731
2099
2444
2807
1621
469
33
97
997
1324
1639
1978
2316
2627
2947
1928
461
60
924
1244
1564
1920
2284
2626
2984
1956
578
34
104
1214
1536
1844
2176
2507
2812
3126
2137
556
116
1140
1455
1769
2117
2472
2804
3152
2116
570
35
187
1453
1765
2064
2386
2707
3002
3307
2314
479
160
1380
1684
1984
2316
2653
2968
3298
2307
519
36
323
1712
2008
2293
2600
2906
3188
3479
2552
506
232
1637
1922
2202
2511
2824
3117
3422
2468
506
37
745
1977
2253
2518
2805
3090
3353
3625
2808
453
599
1891
2154
2412
2696
2983
3251
3530
2692
433
38
1518
2210
2466
2713
2979
3244
3489
3741
2983
395
1399
2111
2355
2595
2857
3122
3369
3626
2867
396
39
2145
2369
2615
2852
3108
3363
3598
3841
3119
382
2164
2273
2505
2732
2980
3231
3465
3707
2981
377
40
2140
2445
2692
2930
3187
3443
3680
3924
3187
390
2160
2369
2595
2816
3058
3302
3529
3765
3078
366
41
475
2471
2725
2969
3233
3496
3739
3990
3205
421
507
2409
2632
2850
3090
3331
3555
3788
3040
370
42 53 2480 2742 2994 3266 3537 3788 4046 3080 391 57 2429 2651 2869 3106 3346 3569 3801 3019 404

GA = Gestational Age (weeks), N = Number of babies in each group, C3 – C97 = Predicted Smoothed percentiles from GAMLSS model Mean & SD = Arithmetic Mean and standard deviation in each group.


[TableWrap ID: T3] Table 3 

Agreement between unadjusted and adjusted centiles


 
 
Adjusted centiles
 
 
 
 
    < 10th 10 – 90th > 90th Weighted kappa P value
First born male babies: (N = 1217)
 
 
 
 
 
 
Unadjusted centiles
< 10th
105
8
0
 
 
10 – 90th
20
943
18
0.883
< 0.001
> 90th
0
6
117
 
 
Later born male babies: (N = 8739)
 
 
 
 
 
 
Unadjusted centiles
< 10th
810
43
0
 
 
10 – 90th
102
6791
101
0.917
< 0.001
> 90th
0
25
867
 
 
First born female babies: (N = 1121)
 
 
 
 
 
 
Unadjusted centiles
< 10th
98
8
0
 
 
10 – 90th
12
874
16
0.897
< 0.001
> 90th
0
6
107
 
 
Later born female babies: (N = 8353)
 
 
 
 
 
 
Unadjusted centiles
< 10th
787
10
0
 
 
10 – 90th
89
6551
65
0.934
< 0.001
  > 90th 0 37 814    


Article Categories:
  • Research Article

Keywords: Reference, Foetal growth, Birth weight, Gestational age, Preterm, Modelling, Box–Cox t, Cubic spline smoothing.

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