1. Characteristics of pregnant women in different groups
Table 1 and Table 2show participants’ characteristics among three groups, including but not limited to maternal age, height, weight, BMI, SBP, and DBP. Data were available for 212 participants after exclusions. The mean maternal age at recruitment was 29 years. UIC/UCr had an overall mean of 208.22 µg/g, and a median of 180.36 µg/g. The mean of UIC was 186.95 µg/l, and the median was 200 µg/l.
Table 1
Characteristics of pregnant women in different UIC groups
|
UIC < 150ug
N = 83
|
150 ≤ UIC < 249ug
N = 63
|
UIC ≥ 250ug
N = 66
|
p
|
age
|
30(28,33)
|
30(27,32)
|
30(28,33)
|
0.530
|
FBG
|
4.42(4.11,4.64)
|
4.38(4.15,4.66)
|
4.34(4.16,4.55)
|
0.737
|
PBG-1h
|
7.76(6.62,8.74)
|
7.815(6.44,8.85)
|
8.39(7.3,9.40)
|
0.143
|
PBG-2h
|
6.92(5.73,7.84)
|
6.645(6.14,8.01)
|
7.04(6.21,8.1)
|
0.725
|
TSH
|
2.19(1.54,3.10)
|
2.175(1.33,3.32)
|
2.47(1.83,3.33)
|
0.660
|
FT3
|
3.82(3.41,4.25)
|
3.89(3.49,4.24)
|
3.92(3.32,4.34)
|
0.928
|
FT4
|
13.08(11.49,14.31)
|
12.67(11.59,13.93)
|
12.72(11.34,14.46)
|
0.685
|
SBP
|
118(113,126)
|
119.5(114,126)
|
120(112,128)
|
0.457
|
DBP
|
74(66,82)
|
76(72,80)
|
73(70,80)
|
0.364
|
height
|
163(160,165)
|
163(160,166)
|
162(160,165)
|
0.474
|
weight
|
70.5(66.5,74)
|
70.75(66.1,76)
|
71.5(63.5,80)
|
0.918
|
BMI
|
26.56(24.98,28.65)
|
26.5(25.07,29.3)
|
27.07(24.84,30.08)
|
0.938
|
TPOAb
|
16
|
13
|
11
|
0.881
|
multiple
|
13
|
17
|
16
|
0.214
|
Table 2
Characteristics of pregnant women in different UIC/Ucr groups
|
UIC/UCr < 106.96ug/g
N = 53
|
106.96 ≤ UIC/UCr < 259.08ug/g
N = 106
|
UIC/UCr ≥ 259.08ug/g
N = 53
|
p
|
age
|
30(27,33)
|
30(28,33)
|
30(27,32)
|
0.803
|
FBG
|
4.375(4.09,4.58)
|
4.37(4.18,4.66)
|
4.35(4.16,4.58)
|
0.881
|
PBG-1h
|
7.68(6.62,8.43)
|
8.1(6.89,9.34)
|
8.12(7.15,9.39)
|
0.177
|
PBG-2h
|
6.88(5.92,7.81)
|
6.82(5.73,7.85)
|
6.75(6.23,8.1)
|
0.457
|
TSH
|
2.055(1.49,3.03)
|
2.31(1.54,3.08)
|
2.8(1.82,3.69)
|
0.234
|
FT3
|
3.73(3.35,4.2)
|
3.94(3.61,4.32)
|
3.8(3.34,4.31)
|
0.353
|
FT4
|
13.36(11.65,15.2)
|
12.83(11.5,14.24)
|
12.53(11.14,13.72)
|
0.137
|
SBP
|
118.5(114,124)
|
119(113,127)
|
120(112,128)
|
0.783
|
DBP
|
75(66,82)
|
76(70,80)
|
72(69,77)
|
0.453
|
height
|
164(160,167)
|
163(158,165)
|
161(160,165)
|
0.026*
|
weight
|
72(67,78)
|
70.5(66,75)
|
70(64,78)
|
0.521
|
BMI
|
26.46(25.04,28.69)
|
26.81(24.84,29.62)
|
27.06(24.77,29.62)
|
0.992
|
TPOAb
|
12
|
22
|
6
|
0.276
|
multiple
|
8
|
29
|
9
|
0.142
|
*Among the four groups, P < 0.05.
SBP: systolic blood pressure, DPB: diastolic blood pressure, TSH: thyroid stimulating hormone, FT4: free thyroxine, FT3: free triiodothyronine, TPOAb: anti-thyroid peroxidase antibody, FBG: fasting blood glucose, PBG-1h: 1hour post-load blood glucose, PBG-2h: 2hour post-load blood glucose.
2. Correlation between blood glucose, thyroid function, and UIC/UCr.
There was a trend towards an association of a lower UIC/UCr with a higher FT4 (P = 0.043), FT3 (P = 0.319), and with a lower TSH (P = 0.162)(Fig. 1. Figure 2). There was no association of UIC with the FT4(P = 0.685), FT3(P = 0.928), and TSH(P = 0.660).
UIC/UCr was has a positive trend but but did not reach statistical significance with TSH (r = 0.096, p = 0.162) and negatively with FT3(r=-0.069, p = 0.319), and FT4(r=-0.139, p = 0.043).
3. Pregnancy outcomes in different iodine nutrition status groups.
Except for LBW (p = 0.007) and PROM (p = 0.03), we observed no statistical difference among UIC/Ucr groups in other pregnancy-related complications and adverse outcomes.(Table 4). We found that the low UIC/UCr may increase the incidence of LBW. In addition to this, when grouped by UIC, the incidence of pregnancy-related adverse outcomes did not differ significantly among groups(Table 3).
Table 3
Pregnancy outcomes in different UIC groups
|
UIC<150ug
N=83
|
150≤UIC<249ug
N=63
|
UIC≥250ug
N=66
|
P
|
Preeclampsia
|
2
|
0
|
3
|
0.277
|
gestational diabetes
|
21
|
16
|
16
|
1.00
|
placenta previa
|
3
|
1
|
0
|
0.315
|
PROM
|
15
|
13
|
18
|
0.409
|
placental abruption
|
1
|
0
|
0
|
1.00
|
preterm delivery
|
8
|
3
|
4
|
0.529
|
cesarean
|
16
|
21
|
14
|
0.367
|
cord around neck
|
12
|
13
|
12
|
0.616
|
low birth weight
|
9
|
3
|
4
|
0.369
|
macrosomia
|
9
|
7
|
6
|
0.921
|
Low Apgar score(1min)
|
4
|
0
|
2
|
0.288
|
Low Apgar score(5min)
|
1
|
0
|
0
|
1.00
|
Table 4
Pregnancy outcomes in different UIC/Ucr groups
|
UIC/UCr<106.96ug/g
N=53
|
106.96≤UIC/UCr<259.08ug/g
N=106
|
UIC/UCr≥259.08ug/g
N=53
|
P
|
Preeclampsia
|
1
|
3
|
1
|
1.00
|
gestational diabetes
|
12
|
26
|
15
|
0.80
|
placenta previa
|
2
|
2
|
0
|
0.37
|
PROM
|
15
|
15
|
16
|
0.03*
|
placental abruption
|
0
|
1
|
0
|
1.00
|
preterm delivery
|
7
|
6
|
2
|
0.148
|
cesarean
|
16
|
21
|
14
|
0.232
|
cord around neck
|
11
|
16
|
10
|
0.686
|
low birth weight
|
8
|
8
|
0
|
0.007*
|
macrosomia
|
8
|
8
|
6
|
0.341
|
Low Apgar score(1min)
|
2
|
3
|
1
|
1.00
|
Low Apgar score(5min)
|
0
|
1
|
0
|
1.00
|
*p<0.005 the comparison of the three groups in the chi-square test is statistically significant
4. Univariate analysis and multivariate regression analysis of LBW.
Consequently, we further investigated the associations between LBW and UIC/UCr. In order to better control the impact of confounders, we matched each pregnant woman with LBW to two women without LBW based on age (± 2 years) and BMI (± 0.3). Logistic regression analysis was performed in Fig. 3 and found that higher UIC/UCr(p = 0.028) as well as TSH(p = 0.022) could significantly reduce the occurrence of LBW. After adjusting covariates including blood glucose, FT4, and FT3, the ORs were still significant. It was found that UIC/UCr was an independent factor for LBW (p = 0.033, OR = 0.991, 95%CI (0.983,0.999)). The ROC curve showed that the AUC for UIC/UCr predicting the incidence of LBW was 0.687 (p = 0.013, 95%CI 0.575, 0.799) (Fig. 4). The optimal cut-off point of UIC/Ucr for the risk of LBW was 200.645ug/g. The risk of low birth weight was higher when the maternal UIC/UCr was less than cut-off point.
Table 5
Multivariate regression analysis of LBW
|
Crude model
|
Adjust model
|
p
|
95%CI
|
P
|
95%CI
|
UIC/UCr
|
0.026
|
0.993(0.986,0.999)
|
0.033
|
0.991(0.983,0.999)
|
TSH
|
0.016
|
0.414(0.202,0.847)
|
0.022
|
0.409(0.190,0.881)
|
Adjust model: FT3 and FT4 are adjusted in adjust model