The flow chart of participants in this birth cohort study was shown in Fig. 1. After excluding the mothers who were none inhabitant and had no health care records (n=265), refused to investigate (n=45), did not complete the PPD scale (n=16), 960 mother-infant pairs were included in our study. Besides, there were 8 (0.8%), 23 (2.5%), 30 (3.2%), 43 (4.7%) infants who were lost to follow-up at 3 months, 6 months, 8 months, and 12months, respectively.
Background data of the involved 960 maternal-infant pairs between maternal PPD and the non-PPD group were listed in Table 1. In total, 77 mothers reported PPD 1 month after delivery, and the prevalence of maternal PPD was 8.0%. Mothers who had pregnancy disease, more daily use to mobile phones during pregnancy, lower average monthly household income, premature and low birth weight infants were more likely to reported PPD, while mothers who were obese before pregnancy reported lower rates. Further, depressed mothers were more towards mix and artificial feeding in the first month of their infants (see Table 1).
Table 1 Sample maternal and infant characteristics categorized by maternal postpartum depression
Characteristics
|
Total(n=960)
|
PPD(n=77)
|
Non-PPD(n=883)
|
χ2
|
P
|
Maternal characteristics
|
|
|
|
|
|
Age (years)
|
|
|
|
5.61
|
0.132
|
<25
|
48
|
7(14.6)
|
41(85.4)
|
|
|
25-29
|
446
|
39(8.7)
|
407(91.3)
|
|
|
30-34
|
343
|
26(7.6)
|
317(92.4)
|
|
|
≥35
|
120
|
5(4.2)
|
115(95.8)
|
|
|
Education
|
|
|
|
0.35
|
0.840
|
Junior school or below
|
33
|
3(9.1)
|
30(90.9)
|
|
|
Senior high school
|
117
|
11(9.4)
|
106(90.6)
|
|
|
Bachelor degree or above
|
797
|
63(7.9)
|
734(92.1)
|
|
|
Pre-pregnancy BMI (kg/m2)A
|
|
|
|
6.35
|
0.042*
|
<24
|
185
|
17(9.2)
|
168(90.8)
|
|
|
24-27.9
|
463
|
45(9.7)
|
418(90.3)
|
|
|
≥28
|
294
|
14(4.8)
|
280(95.2)
|
|
|
History of gestation
|
|
|
|
2.06
|
0.103
|
Primiparous
|
484
|
32(6.2)
|
452(93.4)
|
|
|
Multiparous
|
475
|
45(9.5)
|
430(90.5)
|
|
|
Pregnancy disease
|
|
|
|
11.73
|
0.001*
|
Yes
|
119
|
19(16.0)
|
100(84.0)
|
|
|
No
|
831
|
57(6.9)
|
774(93.1)
|
|
|
Daily use of mobile phones during pregnancy
|
|
|
|
21.14
|
<0.001*
|
Frequent use
|
321
|
44(13.7)
|
277(86.3)
|
|
|
Infrequent use
|
639
|
33(5.2)
|
606(94.8)
|
|
|
Average monthly household income (RMB) B
|
|
|
|
6.25
|
0.044*
|
≤2000
|
30
|
5(16.7)
|
25(83.3)
|
|
|
2001-5000
|
495
|
47(9.5)
|
448(90.5)
|
|
|
>5000
|
408
|
25(6.1)
|
383(93.9)
|
|
|
Feeding pattern of infants from birth to 1 monthsB
|
|
|
|
118.42
|
<0.001*
|
Breastfeeding
|
784
|
48(6.1)
|
736(93.9)
|
|
|
Mixed feeding
|
157
|
24(15.3)
|
133(84.7)
|
|
|
Artificial feeding
|
19
|
25(26.3)
|
14(73.7)
|
|
|
Feeding pattern of infants from 1 to 3 months
|
|
|
|
5.41
|
0.067
|
Breastfeeding
|
642
|
45(7.0)
|
597(93.0)
|
|
|
Mixed feeding
|
93
|
13(14.0)
|
80(16.0)
|
|
|
Artificial feeding
|
212
|
17(8.0)
|
195(92.0)
|
|
|
Feeding pattern of infants from 3 to 6 months
|
|
|
|
3.49
|
0.175
|
Breastfeeding
|
203
|
17(8.4)
|
186(91.6)
|
|
|
Mixed feeding
|
220
|
23(10.5)
|
197(89.5)
|
|
|
Artificial feeding
|
510
|
33(6.5)
|
477(93.5)
|
|
|
Feeding pattern of infants from 6 to 8 months
|
|
|
|
0.71
|
0.702
|
Breastfeeding
|
87
|
5(5.7)
|
82(94.3)
|
|
|
Mixed feeding
|
342
|
29(8.5)
|
313(91.5)
|
|
|
Artificial feeding
|
491
|
39(7.9)
|
452(92.1)
|
|
|
Feeding pattern of infants from 8 to 12 months
|
|
|
|
1.53
|
0.465
|
Breastfeeding
|
38
|
5(13.2)
|
33(86.8)
|
|
|
Mixed feeding
|
619
|
48(7.8)
|
571(92.2)
|
|
|
Artificial feeding
|
242
|
18(7.4)
|
224(92.6)
|
|
|
Infant characteristics
|
|
|
|
|
|
Gender
|
|
|
|
0.34
|
0.559
|
Male
|
493
|
42(8.5)
|
451(91.5)
|
|
|
Female
|
467
|
35(7.5)
|
432(92.5)
|
|
|
Gestational week(weeks)
|
|
|
|
5.50
|
0.019*
|
<37
|
46
|
8(17.4)
|
38(82.6)
|
|
|
≥37
|
898
|
69(7.7)
|
829(92.3)
|
|
|
Birth weight (g)
|
|
|
|
7.54
|
0.023*
|
<2500
|
28
|
6(21.4)
|
22(78.6)
|
|
|
2500-3999
|
865
|
68(7.9)
|
797(92.1)
|
|
|
≥4000
|
60
|
3(5.0)
|
57(95.0)
|
|
|
Note: PPD: postpartum depression, Non-PPD: none of the postpartum depression. Values are n (%). Level of significance: * p<0.05. A: Obese mothers before pregnancy were lower in reported rate of PPD (P<0.001). B: All pairwise comparison within the group were significant (P<0.01).Due to the missing value of some variables, the total number of cases in subgroups was slightly different from the total number of cases.
The measurement results of weight in infants at different months were listed in Table 2. The result of repeated measures ANOVA showed infant weight was linearly gained by month with the largest type III square and mean square (F=22232.89,P<0.05) and there was a difference between depressed and non-depressed mothers over the 12-months (F=6.76,P<0.01). Thus, we considered using the linear model as the basic mixed model to fit the growth trajectory of infant weight, and added the interaction covariates of infant gender (F=14.62, P<0.001) and birth weight (F=14.62, P<0.001) with month-old to model to examine the effect of maternal PPD on weight growth of infant during different periods. Ultimately, estimated fixed-effect parameters of maternal PPD in the final LMM models at five different periods of 1-12 months were shown in Table 3. Furthermore, effects parameter estimations of maternal PPD on underweight of infants in final GEEs models were shown in Table 4.
LMM analyses indicated that maternal PPD was negatively associated with infant weight from 1 to 12 months (P<0.05) (see Table 3). GEEs analyses found that maternal PPD was positively related to infant underweight from 1 to 3 months (P<0.05) (see Table 4). On closer analysis, the average weights of infants with maternal PPD were 0.14kg, 0.13kg, 0.13kg, 0.13kg, and 0.16kg lighter than that without PPD at 1 month, 1-3 months, 1-6 months, 1-8 months, and 1-12 months respectively (see Table 3). Then, the risks of being underweight in maternal PPD infants were 3.19 times and 3.19 times higher than that none of PPD at 1 month and 1-3 months accordingly (see Table 4).
Table 2 Weight measurements of infants among depressed and non-depressed mothers at different months
Month
|
PPD
|
|
Non-PPD
|
M
|
SD
|
|
M
|
SD
|
1 month
|
4.22
|
0.67
|
|
4.53
|
0.55
|
3 months
|
6.41
|
0.82
|
|
6.66
|
0.76
|
6 months
|
7.99
|
0.8
|
|
8.17
|
0.9
|
8 months
|
8.72
|
0.88
|
|
8.91
|
0.98
|
12 months
|
9.55
|
0.86
|
|
9.79
|
1.05
|
Note: PPD: postpartum depression, Non-PPD: none of the postpartum depression, M: mean, SD: standard deviation.
Table 3 Fixed effects estimation of maternal PPD in LMM models at different periods
Models (normal as control)
|
β (95%CI)
|
Sβ
|
t
|
P
|
Mode 1(1 months )
|
- 0.14(-0.25, -0.02)
|
0.06
|
-2.38
|
0.017*
|
Mode 2(1 to 3 months)
|
-0.13(-0.24, -0.02)
|
0.06
|
-2.31
|
0.020*
|
Mode 3 (1 to 6 months)
|
-0.13(-0.24, -0.02)
|
0.05
|
-2.29
|
0.022*
|
Mode 4 (1 to 8 months)
|
-0.13(-0.24, -0.02)
|
0.06
|
-2.24
|
0.025*
|
Mode 5 (1 to 12 months)
|
-0.16(-0.27, -0.04)
|
0.06
|
-2.79
|
0.005*
|
Note: Level of significance:* p<0.05. Model1: 2lnL=1085.10, AIC=1129.10, and BIC=1233.91. Model 2: 2lnL=2633.53, AIC=2691.53, and BIC=2849.26.Model 3: 2lnL=4121.22, AIC=4197.23, and BIC=4418.53. Model 3: 2lnL=5313.73, AIC=5409.74, and BIC=5702.21. Model 4: 2lnL=6682.27, AIC=6680.27, and BIC=7170.70.
Table 4 Effects estimation of maternal PPD on underweight infants in GEE models during different periods of 1-12 months
Models(normal as control)
|
Underweight (%)
|
RR (95%CI)
|
Wald χ2
|
P
|
PPD
|
Non-PPD
|
Mode 1(1 month )
|
9.46%
|
2.83%
|
3.19(1.38, 7.34)
|
7.42
|
0.006*
|
Mode 2(1 to 3 months)
|
6.80%
|
2.08%
|
3.19(1.32, 7.70)
|
6.67
|
0.010*
|
Mode 3 (1 to 6 months)
|
5.00%
|
1.78%
|
2.52(0.98, 6.45)
|
1.86
|
0.055
|
Mode 4 (1 to 8 months)
|
3.72%
|
1.67%
|
1.99(0.75, 5.27)
|
1.90
|
0.168
|
Mode 5 (1 to 12 months)
|
3.01%
|
1.74%
|
1.37(0.54, 3.50)
|
0.45
|
0.505
|
|
|
|
|
|
|
|
Note: PPD: postpartum depression, Non-PPD: none of the postpartum depression. Level of significance:* p<0.05. Model1 adjusted the variable of maternal pre-pregnancy BMI (QIC=271.19). Model 2 adjusted the variable of maternal pre-pregnancy BMI (QIC=422.76), Model 3 adjusted the variable of maternal pre-pregnancy BMI (QIC=551.28). Model 4 adjusted the variable of maternal pre-pregnancy BMI (QIC=654.48). Model 5 adjusted the variable of maternal pre-pregnancy BMI and parity (QIC=826.31).