Anthropometry was recorded in 3719 pregnant women, and the mean age was 24.2 years. Majority of them had attained middle school education (91.2%), 22.7% had parents with diabetes, 45.1% of them were primiparous, women largely were homemakers (92.6%), and one in nine (11.1%) women were diagnosed with GDM during the current pregnancy. Of the 3719 pregnant women, 2962 completed the lab tests, there were 60 cases of child death, 290 women had not delivered as of the analysis date, and there were 180 cases lost to follow up. Infant anthropometry was measured in 2432 infants. The mean birth weight was 3.07(SD ± .736) kg, and the total skinfold thickness was 14.20 mm. The mean gestational age at delivery was 38.6 weeks. The characteristics of the study population are summarized in Table 1.
Table 1
Demographic characteristics of participants (N = 3719)
Characteristics
|
n(%)
|
Maternal characteristics (n = 3720)
|
Maternal age in years (Mean ± SD)
|
24.26 ± 4.08
|
Gestational age at recruitment in weeks (Mean ± SD)
|
23.5 ± 6.01
|
Religion
|
|
Hinduism
|
1876(50.40%)
|
Islam
|
1696(45.60%)
|
Other*
|
147(4.00)
|
Education
|
|
Primary School and below
|
337(9.00%)
|
Middle School and above
|
3382 (91.00%)
|
Occupation#(N = 3716)
|
|
Homemakers
|
3445(92.60%)
|
Unskilled
|
146(3.90%)
|
Semi-skilled/ Skilled
|
125(3.40%)
|
Husband’s occupation#(N = 3716)
|
|
Unemployed
|
13(0.30%)
|
Unskilled
|
1767(47.50%)
|
Semi-skilled
|
1182(31.80%)
|
Skilled
|
754(20.30%)
|
Gravida
|
|
Primigravida
|
1467(39.40%)
|
Multigravida
|
2252(60.60%)
|
Parity
|
|
Nulliparous
|
1667(44.80%)
|
Primiparous
|
1677(45.10%)
|
Multiparous
|
375(10.10%)
|
History of abortion
|
|
0
|
2997(80.60%)
|
1
|
601(16.20%)
|
> 2
|
121(3.30%)
|
Current gestational diabetes status during the assessment
|
|
Yes
|
417(11.10%)
|
No
|
3302(88.80%)
|
Blood pressure (N = 3688)
|
|
Systolic blood pressure (mm of Hg)
|
101 ± 11.0
|
Diastolic blood pressure (mm of Hg)
|
63.4 ± 9.0
|
Family history of diabetes
|
|
None
|
2874(77.20%)
|
One Parent
|
745(20.02%)
|
Both parent
|
101(2.71%)
|
Anthropometry measurements
|
|
Weight (kg) (Mean ± SD)
|
58.95 ± 11.72
|
Height (cm) (Mean ± SD)
|
153.9 ± 5.72
|
Mid-upper arm circumference(cm) (Mean ± SD)
|
26.0 ± 3.87
|
Biceps skinfold thickness (mm) (Mean ± SD)
|
10.63 ± 4.90
|
Triceps skinfold thickness (mm) (Mean ± SD)
|
19.56 ± 5.98
|
Subscapular skinfold thickness (mm) (Mean ± SD)
|
17.26 ± 6.00
|
Sum of skinfold thickness (mm) (Mean ± SD)
|
47.45 ± 14.8
|
Delivery outcomes (n = 2432)
|
|
Gestational age at delivery in weeks (Mean ± SD)
|
38.6 ± 1.6
|
Delivery type
|
|
Vaginal delivery
|
1341(55.10%)
|
Caesarean delivery
|
1092(44.90%)
|
Infant characteristics (n = 2432)
|
|
Sex
|
|
Male
|
1257(51.70%)
|
Female
|
1175(48.30%)
|
Age at assessment in days (Mean ± SD)
|
12.1 ± 19.3
|
Anthropometry measurements
|
|
Weight (kg) (Mean ± SD)
|
3.07 ± .736
|
Length (cm) (Mean ± SD)
|
49.55 ± 3.88
|
Crown-rump length (cm) (Mean ± SD)
|
32.59 ± 3.21
|
Head circumference (cm) (Mean ± SD)
|
33.76 ± 2.16
|
Chest circumference (cm) (Mean ± SD)
|
32.33 ± 2.81
|
Waist circumference (cm) (Mean ± SD)
|
30.75 ± 3.72
|
Hip circumference (cm) (Mean ± SD)
|
29.16 ± 3.72
|
Mid-upper arm circumference(cm) (Mean ± SD)
|
9.89 ± 1.22
|
Biceps skinfold thickness (mm) (Mean ± SD)
|
4.05 ± 1.17
|
Triceps skinfold thickness (mm) (Mean ± SD)
|
5.19 ± 1.48
|
Subscapular skinfold thickness (mm) (Mean ± SD)
|
4.97 ± 1.38
|
Sum of skinfold thickness (mm) (Mean ± SD)
|
14.20 ± 3.69
|
SD, standard deviation; *Others: Christian and Jain; #Occupation: Unskilled: labourer, construction labourer, helper, attender; Peon, cleaner, sweeper, Semi-Skilled: Gatekeeper/Security, Asst. Operator, Asst. electrician, waiter, Skilled: Tailor, carpenter, Driver, plumber, electrician |
The optimum cut-off values for the various anthropometric measurements corresponding to the 90th percentile cut-off of the total maternal skinfold thickness is shown in Table 2. Although the cut-off values obtained via different ROC curve methods were not identical, they approximated each other. Given the discordance, the cut-offs generated using Youden’s J statistic method − 66.89 kg for weight, 53.39 cm for HeadC, 29.20 cm while considering MUAC and 27.82 kg/m2 for BMI – were selected as optimal.
Table 2
Cut-offs for different anthropometric measures corresponding to total skinfold thickness cut-off (90th percentile) in pregnant women, by different methods of ROC curve analysis. [N = 3719]
Anthropometric measure
|
Cut-off corresponding to 90th percentile of total skinfold thickness from different methods
|
Youden's J statistic**
|
Minimized distance to (0, 1) point in the ROC curve
|
Sensitivity-specificity equality
|
Bodyweight (kg)
|
66.89
|
66.89
|
64.94
|
Head circumference (cm)
|
53.39
|
53.39
|
53.09
|
Mid-upper arm circumference (cm)
|
29.2
|
28.5
|
28.3
|
BMI (kg/m2)
|
27.82
|
27.37
|
27.49
|
*Sum of Biceps, Triceps and Sub−scapular skinfold thickness |
** In case of discrepancy between cut−offs determined by different methods, the cut−off obtained via Youden’s J statistic was considered as standard |
Table 3 depicts the resultant distribution of 90th percentile of total skinfold according to the optimal cut-off values for the four maternal anthropometric measures, derived from the ROC curve analyses. MUAC cut-off had the least amount of misclassification (15%), while HeadC cut-off had the highest (worst) misclassification (32.46%). Highest amount of agreement (as per Kappa statistic) with total skinfold was also attributed to MUAC cut-off value (0.42 (95% CI 0.38–0.46)). We found that MUAC cut-off emerged as the best possible substitute for the measurement of total skinfolds in pregnant women (Table 2–3, Figs. 1–2).
Table 3
The magnitude of agreement and the extent of misclassification on using different anthropometric measures instead of total skinfold thickness for measurement of body fat in pregnant women (90th percentile cut off). [N = 3719]
Anthropometric measure
|
Cut-off #
|
Total skin fold thickness percentile
|
Total misclassification (%)
|
Kappa coefficient (95% CI)
|
< 90th percentile
|
> 90th percentile
|
Body weight (kg)
|
< 66.89
|
2799 (75.26)
|
90 (2.42)
|
17.32
|
0.38* (0.34–0.41)
|
≥ 66.89
|
554 (14.90)
|
276 (7.42)
|
Head circumference (cm)
|
< 53.39
|
2304 (61.95)
|
158 (4.25)
|
32.46
|
0.12** (0.1–0.15)
|
≥ 53.39
|
1049 (28.21)
|
208 (5.59)
|
Mid-upper Arm Circumference (cm)
|
< 29.20
|
2885 (77.60)
|
90 (2.42)
|
15.01
|
0.42*** (0.38–0.46)
|
≥ 29.20
|
468 (12.59)
|
275 (7.40)
|
BMI (kg/m2)
|
< 27.82
|
2746 (73.84)
|
81 (2.18)
|
18.5
|
0.36* (0.33–0.40)
|
≥ 27.82
|
607 (16.32)
|
285 (7.66)
|
#Cut off corresponding to 90th percentile of total skinfold thickness |
*Fair agreement; **Slight agreement; ***Moderate agreement [Landis & Koch (1977)] |
Each of the seven anthropometric parameters in the newborns was positively correlated with total skinfold thickness with a statistically significant slope. (Figs. 3–4)
Although the cut-off values, for each of the seven anthropometric measures, produced using different ROC curve methods were not identical, they approximated each other. (Figs. 3–4) The optimum cut-off values for the various anthropometric measurements corresponding to the 85th percentile cut-off of the total maternal skinfold thickness for newborns are shown in Table 4. We found that birth weight in babies was a perfect substitute for skinfold thickness. We also found that HeadC, CC, WC and HC were optimally similar concerning the parameters listed in Table 4. The Youden’s J statistic method revealed the following cut-off values − 3.45 kg for body weight, 35cm for HeadC, 33.7cm for CC, 31.7cm for WC, 30.3cm for HC, 10.30cm for MUAC and 13.22 (kg/m2) for BMI. (Table 4)
Table 4
Cut-offs for different anthropometric measures that correspond to total skinfold thickness cut-off (85th percentile) for children at birth - determined by different methods of ROC curve analysis. [N = 2432]
Anthropometric measure
|
Cut-off corresponding to 85th percentile of total skinfold thickness from different methods
|
Youden's J statistic**
|
Minimized distance to (0, 1) point in the ROC curve
|
Sensitivity-specificity equality
|
Bodyweight (kg)
|
3.45
|
3.40
|
3.26
|
Head circumference (Cm)
|
35.00
|
34.70
|
34.60
|
Chest circumference (Cm)
|
33.70
|
33.70
|
33.40
|
Waist circumference (Cm)
|
31.70
|
32.40
|
32.40
|
Hip circumference (Cm)
|
30.30
|
30.30
|
30.50
|
Mid-upper arm circumference (Cm)
|
10.30
|
10.30
|
10.30
|
BMI (kg/m2)
|
13.22
|
12.87
|
12.88
|
*Sum of Biceps, Triceps and Sub−scapular skinfold thickness |
** In case of discrepancy between cut−offs determined by different methods, the cut−off obtained via Youden’s J statistic was considered as standard. |
Table 5 depicts the extent of misclassification that would result from the use of the newly defined cut-offs instead of the accepted standard, i.e. 85th percentile of total skinfold in newborns along with the amount of agreement (expressed by kappa statistic) between each of the seven measures and total skinfolds cut-off. Our results indicate that the birth weight cut-off (3.45 kg) had the least amount of misclassification (13%) against total skinfold thickness, while BMI cut-off had the highest (worst) misclassification (24.11%). The highest value of kappa statistic was also attributed to Birth weight (0.57 (0.52–0.60)] followed by the head and chest circumferences, respectively. The cut-offs for circumferences at the waist, hip and mid upper arm and BMI showed fair agreement with total skinfold thickness.
Table 5
The magnitude of agreement and the extent of misclassification on using different anthropometric measures instead of total skinfold thickness for measurement of body fat among children at birth (85th percentile cut-off). [N = 2432]
Anthropometric measure
|
Cut-off#
|
Total skin fold thickness percentile
|
Total misclassification (%)
|
Kappa coefficient (95% CI)
|
≤ 85th percentile
|
> 85th percentile
|
Birth weight (kg) [N = 2432]
|
< 3.45
|
1839 (75.62)
|
78 (3.21)
|
13.00
|
0.57*
(0.52–0.60)
|
≥ 3.45
|
238 (9.79)
|
277 (11.39)
|
Head circumference (cm) [N = 2432]
|
< 35.00
|
1699 (69.86)
|
90 (3.70)
|
19.24
|
0.42*
(0.38–0.46)
|
≥ 35.00
|
378 (15.54)
|
265 (10.90)
|
Chest circumference (cm) [N = 2432]
|
< 33.70
|
1718 (70.64)
|
85 (3.50)
|
18.26
|
0.45*
(0.40–0.49)
|
≥ 33.70
|
359 (14.76)
|
270 (11.10)
|
Waist circumference (cm)
|
< 31.70
|
1469 (60.40)
|
52 (2.14)
|
27.14
|
0.34**
(0.31–0.37)
|
≥ 31.70
|
608 (25.00)
|
303 (12.46)
|
Hip circumference (cm)
|
< 30.30
|
1609 (66.16)
|
74 (3.04)
|
22.28
|
0.39**
(0.35–0.43)
|
≥ 30.30
|
468 (19.24)
|
281 (79.15)
|
Mid Upper Arm Circumference (Cm)
|
< 10.30
|
1621 (66.65)
|
78 (3.21)
|
21.96
|
0.39**
(0.35–0.43)
|
≥ 10.30
|
456 (18.75)
|
277 (11.39)
|
BMI (kg/m2)
|
< 13.22
|
1609 (66.19)
|
119 (4.90)
|
24.11
|
0.31**
(0.27–0.35)
|
≥ 13.22
|
467 (19.21)
|
236 (9.71)
|
#Cut off corresponding to 85th percentile of total skinfold thickness |
*Moderate agreement; **Fair agreement [Landis & Koch (1977)] |