Table 1. Odds ratio (OR) for PPD by covariates and distribution of covariates amongst cases and controls.
| Cases(N = 605) | Controls(N = 875) | OR (95%CI) | P* | |
| Delivery year | N (%) | N (%) | ||
| 1998 | 65 (11) | 82 (9) | 1.19 (0.81; 1.74) | 0.93 |
| 1999 | 103 (17) | 151 (17) | 1.02 (0.74; 1.41) | |
| 2000 | 146 (24) | 216 (25) | 1.01 (0.76; 1.36) | |
| 2001 | 133 (22) | 189 (22) | 1.06 (0.78; 1.42) | |
| 2002–2003 | 158 (26) | 237 (27) | 1 (reference) | |
| Maternal age | ||||
| 18–25 | 83 (14) | 111 (13) | 1.13 (0.79; 1.62) | 0.96 |
| 26–28 | 146 (24) | 218 (25) | 1.01 (0.74; 1.37) | |
| 29–30 | 102 (17) | 150 (17) | 1.03 (0.73; 1.43) | |
| 31–33 | 144 (24) | 200 (23) | 1.09 (0.80; 1.48) | |
| 34+ | 130 (22) | 196 (22) | 1 (reference) | |
| Pre-pregnancy BMI | ||||
| Underweight | 26 (4) | 37 (4) | 1.02 (0.61; 1.72) | 0.94 |
| Normal | 377 (62) | 549 (63) | 1 (reference) | |
| Overweight/obese | 172 (28) | 240 (27) | 1.04 (0.82; 1.32) | |
| Missing | 30 (5) | 49 (6) | ||
| Smoking during pregnancy | ||||
| Non-smoker | 362 (60) | 668 (76) | 1 (reference) | <.001 |
| Occasional smoker | 91 (15) | 97 (11) | 1.73 (1.27; 2.37) | |
| Daily smoker < 15 cigarettes | 123 (20) | 86 (10) | 2.64 (1.95; 3.58) | |
| Daily smoker ≥ 15 cigarettes | 23 (4) | 15 (2) | 2.83 (1.46; 5.49) | |
| Missing | 6 (1) | 9 (1) | ||
| Socio economic status | ||||
| High level proficiency | 32 (5) | 80 (9) | 1 (reference) | <.001 |
| Medium level proficiency | 126 (21) | 269 (31) | 1.17 (0.74; 1.86) | |
| Skilled | 85 (14) | 119 (14) | 1.79 (1.09; 2.93) | |
| Student | 63 (10) | 95 (11) | 1.66 (0.99; 2.79) | |
| Unskilled | 135 (22) | 161 (18) | 2.10 (1.31; 3.35) | |
| Unemployed | 113 (19) | 78 (9) | 3.62 (2.19; 5.98) | |
| Missing | 51 (8) | 73 (8) | ||
| Social support | ||||
| Poor social support | 90 (15) | 95 (11) | 1.45 (1.06; 1.98) | 0.02 |
| Good social support | 480 (79) | 734 (84) | 1 (reference) | |
| Missing | 35 (6) | 46 (5) | ||
| Physically active during pregnancy | ||||
| No | 397 (66) | 541 (62) | 1.21 (0.97; 1.52) | 0.10 |
| Yes | 182 (30) | 300 (34) | 1 (reference) | |
| Missing | 26 (4) | 34 (4) | ||
| Parity | ||||
| 0 | 237 (39) | 400 (46) | 1 (reference) | 0.01 |
| 1 + | 343 (57) | 441 (50) | 1.31 (1.06; 1.63) | |
| Missing | 25 (4) | 34 (4) | ||
| Supplement with multivitamin during pregnancy | ||||
| Yes | 513 (85) | 745 (85) | 1 (reference) | 0.86 |
| No | 73 (12) | 109 (12) | 0.97 (0.71; 1.34) | |
| Missing | 19 (3) | 21 (2) | ||
| Gestation week at sample | ||||
| <23 | 35 (6) | 41 (5) | 1.11 (0.68; 1.82) | 0.61 |
| 23 | 103 (17) | 155 (17.71) | 0.87 (0.62; 1.20) | |
| 24 | 153 (25) | 216 (24.69) | 0.92 (0.69; 1.24) | |
| 25 | 152 (25) | 198 (22.63) | 1 (reference) | |
| 26 | 80 (13) | 136 (15.54) | 0.77 (0.54; 1.08) | |
| 27 | 30 (5) | 47 (5.37) | 0.83 (0.50; 1.38) | |
| 28+ | 25 (4) | 47 (5.37) | 0.69 (0.41; 1.18) | |
| Missing | 27 (4) | 35 (4.00) | ||
| Season of sample | ||||
| January-March | 130 (21) | 216 (24.69) | 1 (reference) | 0.43 |
| April-June | 152 (25) | 229 (26.17) | 1.10 (0.82; 1.49) | |
| July-September | 139 (23) | 189 (21.60) | 1.22 (0.90; 1.66) | |
| October-December | 158 (26) | 209 (23.89) | 1.26 (0.93; 1.70) | |
| Missing | 26 (4) | 32 (3.66) |
*
P-value for test for homogeneity.