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  • Research article
  • Open Access
  • Open Peer Review

Reference curves of birth weight, length, and head circumference for gestational ages in Yogyakarta, Indonesia

  • 1Email author,
  • 2,
  • 3,
  • 1 and
  • 4
BMC PediatricsBMC series – open, inclusive and trusted201616:188

https://doi.org/10.1186/s12887-016-0728-1

  • Received: 23 March 2016
  • Accepted: 8 November 2016
  • Published:
Open Peer Review reports

Abstract

Background

The birth weight reference curve to estimate the newborns at risk in need of assessment and monitoring has been established. The previous reference curves from Indonesia, approximately 8 years ago, were based on the data collected from teaching hospitals only with limited gestational ages. The aims of the study were to update the reference curves for birth weight, supine length and head circumference for Indonesia, and to compare birth weight curves of boys and girls, first child and later children, and the ones in the previous studies.

Methods

Data were extracted from the Maternal-Perinatal database between 1998–2007. Only live singletons with recorded gestational ages of 26 to 42 weeks and the exact time of admission to the neonatal facilities delivered or referred within 24 h of age to Sardjito Hospital, five district hospitals and five health centers in Yogyakarta Special Territory were included. Newborns with severely ill conditions, congenital anomaly and chromosomal abnormality were excluded. Smoothening of the curves was accomplished using a third-order polynomial equation.

Results

Our study included 54,599 singleton live births. Growth curves were constructed for boys (53.3%) and girls (46.7%) for birth weight, supine length, and head circumference. At term, mean birth weight for each gestational age of boys was significantly higher than that of girls. While mean birth weight for each gestational age of first-born-children, on the other hand was significantly lower than that of later-born-children. The mean birth weight was lower than that of Lubchenco’s study. Compared with the previous Indonesian study by Alisyahbana, no differences were observed for the aterm infants, but lower mean birth weight was observed in preterm infants.

Conclusions

Updated neonatal reference curves for birth weight, supine length and head circumference are important to classify high risk newborns in specific area and to identify newborns requiring attention.

Keywords

  • Reference curve
  • Birth weight
  • Supine length
  • Head circumference
  • Sex
  • First-later-born children
  • Preterm term

Background

Size at birth reflects fetal growth and health as well as provides important information on the newborns infant. Many studies have been carried out to construct a theoretical birth weight curve for gestational age [1, 2]. The birth size curve was used as a reference to facilitate prediction of growth, estimate the risk for small gestational age (SGA), and to identify newborns at risk that require assessment and monitoring during the neonatal period [37].

The prevalence of high risk newborns depends on the birth curve used [8]. Therefore, a perinatal growth chart that is versatile enough to serve as an international reference and at the same time simple to understand, to reproduce, and to use is needed [9]. However, data suggests that reference curves from other populations may not be representative, thus it is important to develop region-and population-specific reference curves [1016]. Consequently, gender-specific population-based reference curves are expected to improve the clinical assessment of growth in newborns and evaluation of interventions [17]. In addition, update of the reference curves every 10–15 year is necessary to adjust the curves for changes in the population over time [1823]. Hence, fetal growth may be assessed in longitudinal studies, clinically or through ultrasound scans. Nevertheless, birth weight and estimated intrauterine fetal weight are not always comparable especially at earlier periods of gestation. Thus, the birth weight data should not be used to calculate intrauterine growth rate [24].

Today clinicians in most developing countries are using the Lubchenco’s reference curve for newborns [1, 25]. However, most neonatology centers in developed countries in Europe use the Niklasson’s curve [19]. Indonesian clinicians, on the other hand, have emphasized the importance of establishing national reference curves. Alisyahbana’s study developed reference curves for 5844 newborns with 34–44 weeks based on data from 14 teaching hospitals in Indonesia from July 1,1990 to June 30,1991 [26]. The result showed that the mean birth weight of Lubchenco’s newborns was significantly different than that from Alisyahbana’s, therefore the Lubchenco’s curve cannot be used as reference curve for Indonesian newborns.

In 1992 the Maternal-Perinatal (MP) team was established in Yogyakarta with the aim of conducting MP audits and creating an MP database in the district hospitals including data collection on birth weight, supine length and head circumference of newborns. The aims of this study were to update the reference curves for birth weight, supine length and head circumference for Yogyakarta, Indonesia and to compare birth weight curves of boys and girls, first child and later children, and the ones in the previous studies.

Methods

Study population and study period

The study was conducted in Yogyakarta Special Territory (YST) whose population is made up of various ethnics in Indonesia. Nevertheless it has not represented the population of Indonesia as a whole. YST consist of five districts. Each district is served by a district hospital and a couple of health centers, of which only one was equipped for deliveries, and the referral hospital Sardjito. During the study period January 1, 1998 to December 31, 2007 all deliveries at Sardjito Hospital, the five district hospitals, and the five health centers equipped for deliveries were recorded. Approximately, 80% of the newborns in YST were delivered by trained health personnel, 65% of whom were delivered in Sardjito Hospital, five district hospitals and five health centers; the remaining 35% was delivered in private hospitals, maternity clinics, midwife clinics or at home by midwives [27].

Our study population consisted of all newborns delivered at Sardjito Hospital, five district hospitals, five health centers and those referred from other health facilities within 24 h of birth.

Lubchenco [1, 25], Niklasson [19], and Alisyahbana [26] presented birth weight using gestational age curves for singleton, live born, and healthy newborns. The study population of Lubchenco was collected from Colorado General Hospital, Niklassons from the Swedish Medical Birth Register and it covers the whole Sweden, and Alisyahbana from 14 teaching hospitals in Indonesia (Table 1).
Table 1

A comparison of the present study with the previous studies

Reference

Study area

Study population

Study period

Sample size

Subjects

Analysis

     

All/live births

All/Singleton

GA (weeks) Method

Congenital anomalies included

Gender

Mean ± SD by GA

Percentiles by GA

Lubchenco [1, 25]

US (Denver, Colorado)

Colorado General Hospital

1948–61

7827

Live

All

24–42 LMP

No

Yes

No

Yes

Niklasson [19]

Sweden

Medical birth registration

1977–81

475,588

Live

Singleton

28–42 LMP & USG

No

Yes

Yes

No

Kramer [18]

Canada, except Toronto

Provinces

1994–96

676,605

All

Singleton

22–43 USG

Yes

Yes

Yes

Yes

Alisyahbana [26]

Indonesia

14 teaching hospitals

1990–91

5844

Live

Singleton

34-44 LMP

No

Yes

No

Yes

Ulrich M [12]

Denmark (Odense)

Residents

1978

906

Live

Singleton

25–43 USG & Dubowitz

No

Yes

Yes

No

Matthai [24]

India (Velore)

Christian hospital (n = 13,217)

1991–94

11,641

Live

Singleton

37–41 Clinical &USG

No (normal)

Yes

No

Yes (only 10, 50, 90)

Fok [20]

Hongkong

Chinese origin (n = 104,258)

1998–2001

10,339

Live

Singleton

24–43 (USG & Ballard)

No

Yes

Yes

Yes

Visser [21]

The Netherland

The Netherlands Perinatal Registry (n = 183,000)

2001

176,000

Live & intrapartum death

Singleton

25 onwards LMP &USG

Yes

Yes

Yes

Yes

Present study

Indonesia (Yogyakarta)

Sardjito, 5 district hospitals, & 5 health centers (n = 59,609)

1998–2007

54,599

Live

Singleton

26–42 (Dubowitz)

No

Yes

Yes

Yes

Maternal-Perinatal database

The study was conducted by MP team based on MP database. The MP database in the district hospitals is part of MP audit, which is a district-based audit of maternal and perinatal mortality. The MP audit was introduced in Indonesia as a tool for continuous surveillance of the maternal-perinatal mortality and quality assurance of the obstetric and perinatal services into the domain of district health system [28, 29].

The MP database was run in every district hospital by filling in the MP form daily. The data were validated monthly by the local team before they were sent to the MP center at the beginning of the next month and were computerized by a trained secretary. The data generation process from data collection, field editing, data form submission to the data center, and to data entry were continuously monitored to identify errors and logical inconsistencies.

In Indonesia, primary health care services are conducted in health centers. The district hospitals are secondary health facilities that provide referral services in that area. Tertiary health facilities are made available at teaching hospitals, which are usually found in the capital of a province. However, for provinces without a teaching hospital, the services are provided by the provincial hospital, a government hospital in the capital of the province.

The forms from the five district hospitals in YST were submitted to the MP center at Sardjito Hospital until 2001, meanwhile the MP team in the center checked and entered the data. However, from 2002 onwards all facilities were checked and they entered the data by themselves. Therefore the 1998–2001 data were available in the MP center while the 2002–2007 data were available in the health facilities. Unfortunately, an earth-quake struck the area in May 2006 and damaged the soft copy in computers, thus causing most of the data to be re-entered from the MP forms.

The MP database contained information from the mother’s delivery to the neonatal period for each individual in the maternity and newborns facilities in YST. The newborns were followed up until they were discharged from the facilities. Trained health personnel filled in the MP forms. They contained information on identity, characteristics of the mothers, their pregnancy and delivery, and the newborns.

Inclusion and exclusion criteria

Only live singletons with recorded gestational ages between 26 to 42 weeks and the exact time of admission to the neonatal facility were included in the study; meanwhile those with severely ill conditions (severe asphyxia, severe cardio-respiratory distress, etc.), major congenital anomaly, and those admitted >24 h of age were excluded.

Assessment of gestational age

In most developing countries, women especially in rural areas are unaware of the exact date of their last menstrual period (LMP). Thus, they could not calculate the expected date of delivery using the first date of the last menstrual period. Dubowitz [30] developed a clinical assessment of gestational age for newborns. A scoring system for gestational age, based on 10 neurologic and 11 external criteria. The correlation coefficient for the total score against gestation was 0.93. The error of prediction of a single score was 1.02 weeks and of the average of two independent assessments was 0.7 weeks. The method gives consistent results within the first 5 days and is equally reliable in the first 24 h of life. The scoring system is more objective and reproducible than trying to guess the gestational age on the presence or absence of individual signs. In the study, gestational age was based on clinical assessment of gestational age according to Dubowitz score and was verified by the mother’s last normal menstrual period in completed weeks.

Measurements

Birth weight, supine length, and head circumference were measured immediately after delivery. All infants were weighed to the nearest 10 g on a balance scale (readjusted using standardized weight as part of routine care). The length was measured using a measuring board with supports for the head and feet to the nearest cm. The head circumference was recorded using a measuring tape to the nearest cm. Training and standardization in anthropometric measurements of weight, length, head circumference, and clinical assessment of gestational age by Dubowitz score were carried out in December 1997. All measurements were examined by trained nurses.

Data analysis

Data analysis was performed using SPSS version 19. Tables and graphs presented means and standard deviations (SDs) and the 3th, 5th, 10th, 25th, 50th (median), 75th, 90th, 95th, 97th percentiles by gestational age relevant for clinicians in classifying newborns under their care and to researchers as well as public policy makers in comparison to geographic differences and temporal trends in birth weight for gestational ages in population. All analyses were performed separately for boys and girls. Distribution of birth weight, supine length, head circumference at the corrected gestational ages was smoothened by a third degree polynomial function. Curves were produced using Microsoft Excel 2010.

Difference in mean birth weight between boys and girls, as well as first and later-born for each gestational age was analyzed using Student’s t-test. In the birth order of children, the term “first” refers to the 1st child, and “later” refers to second child and so on. The weight-length ratio was calculated according to Rohrer’s Ponderal index (PI); 100 x weight in grams/length [3] in centimeters and was classified by tertiles into 3 groups; low, average, or high [31]. The PI was then calculated and classified into low, average and high.

Results

From January 1998 to December 2007 there were 59,609 births. Most of the infants (83.2%) were born in Sardjito Hospital, five district hospitals, and five health centers, whereas the others (16.8%) were born in other hospitals, health centers, midwife clinics, at home, and were admitted to the study setting before 24 h. In this study there were 54,599 subjects in total. Mean birth weight was 2,964 g and there was no difference in birth weight over time.

Sardjito Hospital, the five district hospitals, and the five health centers in YST contributed with 25%, 56% and 19% of the newborns respectively. First child constituted 26,189 (48.0%) and later child was 28,410 (52.0%). The numbers of eligible infants for birth weight, length and head circumference were 54,599, 52,261 and 48,109 respectively (53.3% boys and 46.7% girls) (Table 2). Mean ± SD, percentiles 3, 5, 10, 25, 50, 75, 90, 95, 97 of birth weight, length, and head circumferences for boys and girls were presented in Tables 3, 4, 5. Smoothed curves of birth weight, length, and head circumference for boys and girls were presented in Figs. 1, 2, 3, 4, 5, 6.
Table 2

Basic characteristics of the study population (n = 54,599)

Characteristic

Category

No

%

Health facility

Sardjito hospital

13,726

25.1

 

District hospitals

30,574

56.0

 

Health centers

10,299

18.9

Gender

Boys

29,112

53.3

 

Girls

25,487

46.7

Birth order

First (1st child)

26,189

48.0

 

Later (≥2nd child)

28,410

52.0

Admitted to neonatal ward

Born in the hospital/health centre

45,414

83.2

Referred <24 h

9,185

16.8

Education of mother (years)

≤5

1,803

3.8

6–12

40,196

82.7

≥13

6,576

13.5

Age of mother (years)

≤19

1,770

3.3

20–34

43,737

81.0

≥35

8,456

15.7

Number of registered infants

Birth weight

54,599

100

Length

52,261

95.7

Head circumference

48,109

88.1

Table 3

Birth weight for boys and girls by gestational age in weeks

GA (w)

No of cases

Mean (g)

SD

Birth weight Percentiles (g)

P3

P5

P10

P25

P50

P75

P90

P95

P97

Boys

26

55

768.1

170.2

500

500

506

600

750

900

1000

1060

1103

27

39

866.6

152.8

520

600

700

750

850

1000

1100

1100

1100

28

50

968.7

152.9

600

600

800

900

1000

1050

1100

1168

1289

29

52

1057

157.0

600

750

900

1000

1085

1130

1235

1331

1412

30

70

1246

202.3

820

950

1000

1100

1205

1400

1547

1623

1667

31

89

1409

282.3

1050

1063

1100

1200

1380

1525

1700

2025

2318

32

223

1705

377.4

1172

1200

1300

1450

1650

1900

2192

2500

2600

33

258

1750

442.7

1200

1200

1250

1400

1700

2000

2219

2562

2837

34

473

1917

407.1

1200

1350

1400

1650

1900

2200

2400

2600

2939

35

541

2035

378.5

1350

1400

1552

1800

2000

2250

2400

2595

2787

36

868

2382

430.7

1650

1750

1900

2100

2350

2550

3000

3216

3400

37

1576

2643

427.1

1800

1999

2150

2450

2600

2900

3200

3400

3500

38

3799

2862

404.8

2100

2200

2400

2600

2800

3100

3400

3550

3700

39

6915

3069

382.3

2310

2496

2600

2850

3050

3300

3500

3700

3800

40

8755

3184

410.5

2414

2540

2700

2950

3180

3400

3700

3900

4000

41

3812

3358

445.0

2500

2600

2800

3100

3400

3650

3900

4000

4200

42

1537

3295

463.5

2500

2600

2800

3000

3250

3500

3950

4182

4300

Girls

26

48

680.8

134.8

500

500

500

600

650

767

900

967

991

27

41

844.3

156.2

600

609

700

770

800

900

1040

1100

1396

28

59

945.3

119.2

600

700

800

900

1000

1000

1100

1100

1166

29

42

1023

109.6

765

800

900

994

1000

1100

1141

1193

1271

30

49

1151

230.2

675

760

850

1000

1100

1300

1500

1575

1665

31

74

1374

294.1

825

975

1100

1200

1340

1500

1725

2050

2200

32

171

1711

441.3

1100

1150

1200

1400

1600

1900

2480

2608

2700

33

211

1692

406.2

1200

1200

1250

1400

1600

1850

2200

2520

2800

34

392

1862

386.5

1200

1250

1400

1568

1875

2100

2300

2400

2500

35

515

2046

386.3

1400

1500

1600

1800

2000

2250

2400

2600

2890

36

812

2335

436.8

1500

1700

1823

2100

2300

2500

2900

3200

3300

37

1384

2589

397.0

1800

1925

2145

2400

2500

2800

3100

3300

3400

38

3318

2800

375.1

2100

2200

2400

2600

2800

3000

3250

3450

3600

39

6065

2997

371.3

2300

2400

2600

2750

3000

3200

3450

3600

3700

40

7607

3099

393.6

2400

2500

2600

2850

3100

3350

3560

3750

3900

41

3254

3259

447.4

2400

2500

2700

3000

3300

3550

3800

4000

4050

42

1445

3208

447.3

2400

2500

2700

2900

3200

3500

3800

4000

4200

GA Gestational Age; SD Standard Deviation; P Percentiles; g gram; w week

Table 4

Length supine of boys and girls by gestational age in weeks

GA (w)

No of cases

Mean (cm)

SD

Lenght Supine Percentiles (cm)

P3

P5

P10

P25

P50

P75

P90

P95

P97

Boys

26

54

33.6

2.73

25

28

31

32

34

35

36

36

37

27

37

33.9

3.88

24

24

25

33

35

36

37

37

40

28

50

35.9

2.94

25

30

35

35

36

37

38

40

43

29

50

37.7

3.18

29

35

35

36

38

39

40

43

45

30

67

39.4

3.01

31

35

36

37

40

41

43

44

44

31

89

41.3

2.02

37

37

39

40

41

42

44

45

45

32

223

42.6

2.27

40

40

40

41

43

44

45

47

47

33

258

42.1

2.89

36

37

38

41

42

44

46

47

48

34

413

43.4

3.08

37

38

40

42

44

46

47

48

49

35

475

44.0

3.19

38

38

40

42

44

46

48

48

49

36

868

45.9

2.01

42

43

44

45

46

47

49

49

50

37

1470

47.0

2.04

43

43

45

46

47

48

49

50

50

38

3778

47.8

1.86

44

45

46

47

48

49

50

50

51

39

6754

48.4

1.74

45

46

47

48

49

50

50

51

51

40

8168

48.8

1.80

45

46

47

48

49

50

51

51

52

41

3584

49.1

2.04

46

46

47

48

49

50

51

52

52

42

1527

49.1

1.76

46

46

47

48

49

50

51

52

52

Girls

26

43

34.1

2.91

26

28

30

33

34

36

37

39

40

27

37

34.8

2.51

25

31

32

34

35

36

38

39

40

28

59

35.9

2.07

33

33

34

35

36

37

40

40

42

29

41

37.7

2.84

30

31

35

36

37

40

42

43

43

30

49

38.8

2.86

34

34

35

36

40

41

42

43

44

31

74

41.3

2.08

38

38

39

40

41

42

45

45

47

32

171

42.9

2.16

40

40

41

41

43

44

46

47

47

33

210

41.9

2.45

37

38

39

40

42

43

45

46

47

34

351

43.1

3.25

37

37

39

41

43

45

47

48

48

35

457

44.0

2.85

38

39

41

42

44

46

48

48

49

36

812

45.7

2.20

41

42

43

45

46

47

48

49

50

37

1304

46.7

1.96

43

43

44

46

47

48

49

50

50

38

3299

47.4

1.78

44

45

45

46

47

49

50

50

51

39

5933

48.0

1.70

45

45

46

47

48

49

50

50

51

40

7074

48.4

1.79

45

46

46

47

48

49

50

51

51

41

3043

48.7

2.04

45

46

47

48

49

50

51

51

52

42

1439

48.8

1.70

45

46

47

48

49

50

51

52

52

GA Gestational Age; SD Standard Deviation; P Percentiles; cm centimeter; w week

Table 5

Head circumference of boys’ and girls’ by gestational age in weeks

GA (w)

No of cases

Mean (cm)

SD

Head Circumferences Percentiles (cm)

P3

P5

P10

P25

P50

P75

P90

P95

P97

Boys

26

50

26.7

2.79

22

22

23

24

26

30

30

30

30

27

33

25.9

2.48

23

23

23

24

25

28

30

31

31

28

42

27.8

3.19

23

23

24

25

27

30

33

33

33

29

35

29.0

2.83

24

25

26

27

28

32

33

33

33

30

63

28.6

1.89

25

25

26

27

29

30

31

31

31

31

89

29.2

1.80

25

26

27

28

29

31

31

32

32

32

223

31.3

1.40

27

28

30

31

32

32

32

33

33

33

256

30.4

1.86

26

27

28

30

31

32

32

33

34

34

398

31.0

1.42

28

29

29

30

31

32

33

34

34

35

465

31.2

1.19

29

29

30

31

31

32

33

33

34

36

868

32.6

1.09

30

31

32

32

33

34

34

34

34

37

669

32.7

1.18

30

30

31

32

33

34

34

34

35

38

3534

33.3

0.871

32

32

32

33

34

34

34

35

35

39

6296

33.7

0.778

32

32

33

34

34

34

35

35

35

40

7871

33.9

0.751

32

32

33

34

34

34

35

35

35

41

3463

34.2

0.763

32

33

34

34

34

35

35

36

36

42

1289

34.1

0.809

32

33

33

34

34

35

35

36

36

Girls

26

36

26.6

2.81

22

22

23

24

26

30

30

30

30

27

31

27.0

2.53

23

24

24

25

26

30

30

30

30

28

46

27.4

3.16

22

23

24

25

27

30

32

33

33

29

31

29.5

2.36

25

26

26

28

30

31

33

33

33

30

41

28.4

2.30

23

23

24

27

29

30

31

31

31

31

74

29.3

1.75

25

26

27

28

30

31

31

32

32

32

171

31.1

1.53

27

28

29

30

32

32

33

33

33

33

207

30.3

1.75

27

27

28

29

30

32

32

33

33

34

342

30.8

1.32

28

28

29

30

31

32

32

33

33

35

452

31.2

1.32

28

29

30

31

31

32

33

33

34

36

812

32.4

1.23

30

30

31

32

32

33

34

34

34

37

608

32.7

1.26

30

30

31

32

33

34

34

34

35

38

3088

33.2

0.848

31

32

32

33

34

34

34

34

35

39

5544

33.6

0.774

32

32

33

34

34

34

35

35

35

40

6817

33.8

0.752

32

32

33

34

34

34

35

35

35

41

2964

34.1

0.778

32

33

33

34

34

35

35

35

36

42

1201

34.0

0.835

32

32

33

34

34

35

35

35

36

GA Gestational Age; SD Standard Deviation; P Percentiles; cm centimeter; w week

Fig. 1
Fig. 1

a Smoothened percentiles for boys’ birth weight by gestational age. b. Smoothened mean and standard deviations for boys’ birth weight by gestational age

Fig. 2
Fig. 2

a Smoothened percentiles for girls’ birth weight by gestational age. b. Smoothened mean and standard deviations for girls’ birth weight by gestational age

Fig. 3
Fig. 3

a Smoothened percentiles for boys’ length by gestational age. b. Smoothened mean and standard deviations for boys’ length by gestational age

Fig. 4
Fig. 4

a Smoothened percentiles for girls’ length by gestational age. b. Smoothened mean and standard deviations for girls’ length by gestational age

Fig. 5
Fig. 5

a Smoothened percentiles for boys’ head circumference by gestational age. b. Smoothened mean standard deviations for boys’ head circumference by gestational age

Fig. 6
Fig. 6

a Smoothened percentiles for girls’ head circumference by gestational age. b. Smoothened mean standard deviations for girls’ head circumference by gestational age

At term (37–42 weeks gestational age) mean birth weight for each gestational age was significantly higher for boys than for girls (Table 6, Fig. 7) and for later born than for first born (Table 7, Fig. 8).
Table 6

Mean birth weight, standard deviation, ponderal index, classification for boys and girls by gestational age

GA (w)

Boys

Girls

p

Boys

Girls

No of cases

Mean (g)

SD

No of cases

Mean (g)

SD

PI

C

PI

C

26

55

768.1

170.2

48

680.8

134.8

0.005

2.1

L

1.7

L

27

39

866.6

152.8

41

844.3

156.2

0.52

2.4

L

2.0

L

28

50

968.7

152.9

59

945.3

119.2

0.37

2.2

L

2.1

L

29

52

1057

157.0

42

1023

109.6

0.25

2.0

L

1.9

L

30

70

1246

202.3

49

1151

230.2

0.019

2.1

L

2.0

L

31

89

1409

282.3

74

1374

294.1

0.45

2.0

L

1.9

L

32

223

1705

377.5

171

1711

441.3

0.87

2.2

L

2.2

L

33

258

1750

442.7

211

1692

406.2

0.15

2.3

L

2.3

L

34

473

1917

407.1

392

1862

386.5

0.043

2.4

L

2.4

L

35

541

2035

378.5

515

2046

386.3

0.64

2.4

L

2.4

L

36

868

2382

430.7

812

2335

436.8

0.026

2.4

L

2.4

L

37

1576

2643

427.1

1384

2589

397.0

<0.001

2.5

A

2.5

A

38

3799

2862

404.8

3318

2800

375.1

<0.001

2.6

A

2.6

A

39

6915

3069

382.3

6065

2997

371.4

<0.001

2.7

A

2.7

A

40

8755

3184

410.5

7607

3099

393.6

<0.001

2.8

A

2.7

A

41

3812

3358

445.0

3254

3259

447.4

<0.001

2.8

A

2.8

A

42

1537

3295

463.5

1445

3208

447.3

<0.001

2.8

A

2.8

A

C Classification; L Low, A Average, H High; GA Gestational Age; SD Standard Deviation; P Percentiles; g gram; w week

Fig. 7
Fig. 7

Mean birth weight for boys’ and girls’ by gestational age

Table 7

Mean birth weight, standard deviation, Ponderal index and classification by birth order and gestational age

GA (w)

First child

Later children

p

First child

Later children

No of cases

Mean (g)

SD

No of cases

Mean (g)

SD

PI

C

PI

C

26

48

723.6

173.7

55

730.7

148.8

0.83

2.0

L

1.9

L

27

40

832.8

145.3

40

877.5

160.8

0.18

2.2

L

2.3

L

28

60

951.6

139.1

49

961.3

132.2

0.71

2.1

L

2.1

L

29

56

1041

107.7

38

1043

175.3

0.94

2.0

L

2.0

L

30

57

1199

203.6

62

1214

232.6

0.70

2.1

L

2.0

L

31

84

1413

315.6

79

1372

254.2

0.37

2.0

L

2.0

L

32

214

1698

393.4

180

1720

421.0

0.58

2.2

L

2.2

L

33

228

1689

407.1

241

1757

443.7

0.083

2.3

L

2.3

L

34

508

1874

386.2

357

1917

414.8

0.12

2.3

L

2.4

L

35

628

2034

361.9

428

2049

410.4

0.54

2.4

L

2.4

L

36

906

2328

390.9

774

2396

477.6

0.002

2.4

L

2.5

A

37

1525

2569

381.3

1435

2669

440.7

<0.001

2.5

A

2.6

A

38

3510

2783

361.3

3607

2883

414.7

<0.001

2.6

A

2.7

A

39

6159

2983

359.5

6821

3083

389.7

<0.001

2.7

A

2.7

A

40

7527

3075

377.2

8835

3204

418.0

<0.001

2.7

A

2.8

A

41

3289

3246

443.1

3777

3370

445.8

<0.001

2.8

A

2.9

H

42

1350

3199

440.7

1632

3297

466.9

<0.001

2.7

A

2.8

A

C Classification; L Low; A Average; H High; GA Gestational Age; SD Standard Deviation; P Percentiles; g gram; w week

Fig. 8
Fig. 8

Mean birth weight for 1st and ≥2nd child by gestational age

For gestational age ≥39 weeks there was a striking similarity in mean birth weight among Lubchenco’s, Alisyahbana’s, and our study. The mean birth weight for gestational age ≤38 weeks was lower in our study than that in Lubchenco’s. Gestational age 34–37 weeks presented the highest mean birth weight in Alisyahbana’s but the lowest in our study (Table 8, Fig. 9).
Table 8

Mean birth weight, Ponderal index, classification in Lubchenco’s, Alisyahbana’s and present study by gestational age

GA (w)

Lubchenco

Alisyahbana

Present study

No of cases

BW (g)

PI

C

No of cases

BW (g)

PI

C

No of cases

BW (g)

PI

C

26

68

1001

2.2

L

    

103

727

1.9

L

27

72

1065

2.2

L

    

80

855

2.1

L

28

118

1236

2.2

L

    

109

956

2.1

L

29

143

1300

2.3

L

    

94

1042

2.0

L

30

109

1484

2.3

L

    

119

1207

2.0

L

31

147

1590

2.4

L

    

163

1393

1.9

L

32

124

1732

2.4

L

    

394

1708

2.2

L

33

118

1957

2.4

L

    

469

1724

2.3

L

34

145

2278

2.5

A

43

2553

2.5

A

865

1892

2.3

L

35

188

2483

2.5

A

70

2704

2.6

A

1056

2040

2.4

L

36

202

2753

2.5

A

136

2849

2.4

L

1680

2359

2.5

A

37

372

2800

2.6

A

262

2819

2.5

A

2960

2618

2.5

A

38

636

3025

2.6

A

565

2903

2.5

A

7117

2833

2.6

A

39

1010

3130

2.6

A

1309

3066

2.6

A

12980

3035

2.7

A

40

1164

3226

2.6

A

1710

3146

2.5

A

16362

3145

2.7

A

41

632

3307

2.6

A

962

3205

2.6

A

7066

3312

2.8

A

42

336

3308

2.6

A

446

3228

2.6

A

2982

3253

2.7

A

Total

5584

   

5503

   

54599

   

C Classification; L Low; A Average; H High; GA Gestational Age; PI Ponderal Index; BW Birth Weight; g gram; w week

Fig. 9
Fig. 9

Mean birth weight by gestational age according to Lubchenco’s, Alisyahbana’s and present study

Tertiles of PI of our study were low (<2.5), average (2.5–2.8) and high (>2.8). The PI of term boys, girls, first and later children in our study were classified into average group. In the preterm, however, it was classified into low group (Tables 6 and 7). The PI for gestational age was consequently lower in our study than in Lubchenco’s. The gestational age ≥39 weeks was higher in our study than it was in Lubchenco’s and Alisyahbana’s (Table 8).

Discussion

Our study presented girls and boys for birth weight, length and head circumference based on the local data. One of the weaknesses of our study was that it did not have enough low-gestational age infants. Therefore the application of the curve in low gestational age infant must be done carefully.

Moreover, comparison of each gestational age showed higher significance in at term only, but not in preterm. The result was similar to the study by Fok [20] whereby the mean birth weight of boys consistently exceeded that of girls at 36 weeks or more gestational ages. Lubchenco [1] showed differences of approximately 100 g, significant between boys and girls at 38 to 41 weeks. Skjaerven [16] explained that the effects at 40 weeks in boys were heavier than those in girls. However, Olsen [32] found that all were statistically different by age group, and most were considered clinically different enough. This illustrates the necessity to create separate charts for boys and girls.

Skjaerven [16] pointed out that later children at 40 weeks were between 130–150 g heavier than first children. This was similar to our study which showed that each gestational age, at term later-born children were significantly 100–130 g heavier (p < 0.001) than first-born children. In preterm there was no significant difference, though. Nevertheless, Alisyahbana reported that for every gestational age and percentile, later-born children were heavier than first born-children [27].

We could not compare the mean birth weight for each gestational age in our study and that in the previous studies by Lubchencho and Alisyahbana, since there was no information on standard deviation. Thus, the comparison was based on mean birth weight for sexes combine because no information of separated boys and girls was found in Alisyahbana’s. Similarly, comparison of our study and Lubchenco’s showed that for gestational age ≤38 weeks the mean birth weight was lower in our study. This was probably due to the relatively high number of infants with small for gestational age in our population for term and preterm, which needed further investigation.

Compared with Alisyahbana’s study, for gestational age 34–37 weeks the mean birth weight was lower in our study; which was probably due to the differences of sample. Our study had more data from health centers, district hospitals, and 1 teaching hospital, whereas Alisyahbana’s study collected the data from 14 teaching hospitals with middle and high socio-economic status. In addition, the numbers of samples in our study were much higher with updated reference for 26 to 42 weeks gestational age, meanwhile Alisyahbana’s was only 34–42 weeks. Unfortunately, we could not compare our result with Niklasson’s curve [20], since we were not able to find the data in the Niklasson’s articles.

Tertiles of PI for our study were similar to those of Morris’s [31] report, which showed <2.6 low, 2.6–2.8 average and >2.8 high. The PI of at term of boys, girls, first, and later children in our study was at average. However, in the preterm it was low.

Lubchenco [26] reported that there was an increasing weight-length ratio (PI) as gestation progressed; the babies became heavier for length as they approached near full term. Similar to our study, PI was classified into preterm and average in near term (35–36 weeks) and term (>37 weeks).

Thus, the combination of short and low PI at birth may well provide a useful classification of the anthropometric status of the newborns. Infants who were born short with low PI were at risk of mortality and severe morbidity during infancy [31]. The low PI of Lubchenco’s was for gestational age ≤33 weeks, whereas it was for ≤35 weeks in our study. If we found a short newborns <35 weeks of gestational age, therefore, he/she would be at high risk for morbidity and mortality.

Important cut off points for risk assessment of the 3rd and 97th percentiles, −2 SD or +2 SD were added. We expect that these curves would be useful for the care of Indonesian newborns.

Conclusions

Our study separated girls and boys for birth weight, length and head circumference based on the local data. At term, mean birth weight of boys was significantly higher than that of girls, mean birth weight of first-born children was significantly lower than that of later born-children; but in preterm, both did not suggest significant difference.

For gestational age ≥39 weeks there was mean birth weight similarity to Lubchenco’s, Alisyahbana’s, and our study. When compared with Lubchenco’s study, the mean birth weight for gestational age ≤38 weeks was lower in our study. However, for 34–37 weeks, the mean birth weight in our study was lower than that in Alisyahbana’s study.

The PI of term for boys and girls and first and later-born children was classified into average, whereas that of preterm was classified into low. The PI for gestational age ≤35 weeks was lower in our study than in Lubchenco’s; however, for gestational age ≥39 weeks it was higher in our study than in Lubchenco’s and Alisyahbana’s.

Updated and improved neonatal reference curves for birth weight, supine length, and head circumference are important to classify high risk newborns in specific area and to recognize those requiring attention with regard to recent condition.

Abbreviations

A: 

Average

C: 

Classification

GA: 

Gestational age

H: 

High

HC: 

Head circumference

L: 

Low

LMP: 

Last menstrual period

MP: 

Maternal-perinatal

PI: 

Ponderal index

SD: 

Standard deviation

SGA: 

Small for gestational age

USG: 

Ultrasonography

YST: 

Yogyakarta special territory

Declarations

Acknowledgements

We would like to thank the late Professor Ahmad Surjono and all the members of MP Audit team of Perinatal Epidemiology team at the Medical Faculty of Gadjah Mada University and all the members of MP Audit team in YST, Yogyakarta Municipality, Districts of Bantul, Kulonprogo, Gunung Kidul, and Sleman. We also thank the physicians, pediatricians, obstetricians, midwives, nurses, and health workers in Sardjito Hospital, the five district hospitals and the five health centers in Tegalrejo, Imogiri, Temon, Ponjong, and Ngemplak. Our gratitude is also addressed to Hans Stenlund, Anneli Ivarsson, Setya Wandita, Tunjung Wibowo, Althaf, Diah, Hilwi, Wulan, Retno, Juwariyem, Kusmiyati, Widodo, Ananta, Shianita, Friska, Toni and Agus Herwindo.

Funding

Not applicable.

Availabillity of data and materials

The data and materials are stored at the Department of Child Health, Neonatology Division, Faculty of Medicine, Universitas Gadjah Mada, Yogyakarta.

Authors’ contributions

All authors participated in the study design and interpretation of data. ELH conceptualized and designed the study, coordinated and supervised data collection, acquisition of data, analysis and interpretation of data, as well as drafted the article. HNL conceptualized and designed the study, analyzed and interpreted the data, and conducted a critical review. Md H designed the data collection instruments, coordinated and supervised the data collection, acquired the data, and drafted the article. EPP carried out the initial analysis of the study. LN conceptualized and designed the study, carried out analysis and interpretation of the data, and drafted the initial article. All authors read and approved the final manuscript.

Competing interests

The authors have indicated they have no financial relationships relevant to this article to disclose. This manuscript does not have conflict of interest with any individual or institution.

Consent for publication

We shall not display the data/photos/videos of the subject of the study.

Ethics approval and consent to participate

This study has been approved by Medical and Health Research Ethics Committee Faculty of Medicine Universitas Gadjah Mada–Dr. Sardjito General Hospital.

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Authors’ Affiliations

(1)
Department of Child Health, Faculty of Medicine, Gadjah Mada University, Sardjito General Hospital, Jl. Kesehatan No. 1, Yogyakarta, 55284, Indonesia
(2)
Department of Pediatrics, Vrije Universiteit Medical Center, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands
(3)
Faculty of Medicine, Gadjah Mada University/Sardjito General Hospital, Jl. Kesehatan No. 1, Yogyakarta, 55284, Indonesia
(4)
Public Health and Clinical Medicine, Umeå University, SE-901 87 Umeå, Sweden

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Copyright

© The Author(s). 2016

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