Variables remaining in the final model (conditional and unconditional analysis)
| Variables | Categories | Cases n=142 | Controls n=550 | Conditional multivariable | Unconditional multivariable |
| n (%) | n (%) | OR (95% CI) | OR (95% CI) | ||
| Maternal age (per year) | 0.93 (0.87 to 0.99) | 0.93 (0.89 to 0.98) | |||
| Ethnicity* | European | 31 (21.8) | 255 (46.4) | 1.00 | 1.00 |
| Pacific | 25 (17.6) | 115 (20.9) | 2.49 (1.00 to 6.20) | 2.27 (1.07 to 4.81) | |
| Asian | 5 (3.5) | 50 (9.1) | 2.47 (0.69 to 8.79) | 2.47 (0.75 to 8.16) | |
| Other | 3 (2.1) | 23 (4.2) | 2.13 (0.25 to 18.08) | 3.09 (0.54 to 17.63) | |
| Māori | 78 (54.9) | 107 (19.5) | 4.39 (1.83 to 10.49) | 3.81 (1.97 to 7.34) | |
| Other social history † | No | 67 (47.2) | 444 (80.7) | 1.00 | 1.00 |
| Unknown | 57 (40.1) | 89 (16.2) | 1.94 (0.39 to 9.61) | 1.33 (0.37 to 4.76) | |
| Yes | 18 (12.7) | 17 (3.1) | 2.32 (0.65 to 8.31) | 3.17 (1.19 to 8.42) | |
| Partner status | Married | 27 (19.0) | 309 (56.2) | 1.00 | 1.00 |
| Unknown | 24 (16.9) | 46 (8.4) | 1.50 (0.50 to 4.52) | 1.6 (0.69 to 3.74) | |
| De facto‡ | 45 (31.7) | 111 (20.2) | 2.50 (0.96 to 6.52) | 2.63 (1.23 to 5.61) | |
| Single | 46 (32.4) | 84 (15.3) | 4.47 (1.54 to 13.01) | 3.84 (1.73 to 8.52) | |
| Unknowns§ | 0 | 47 (33.1) | 372 (67.6) | 1.00 | 1.00 |
| 1 vs 0 | 40 (28.2) | 95 (17.3) | 10.20 (3.41 to 30.52) | 4.71 (2.36 to 9.39) | |
| 2+ vs 0 | 55 (38.7) | 83 (15.1) | 23.06 (3.54 to 150.01) | 9.56 (2.35 to 38.95) | |
| Supplements¶ | Yes | 19 (13.4) | 130 (23.6) | 1.00 | 1.00 |
| Unknown | 69 (48.6) | 222 (40.4) | 1.54 (0.56 to 4.23) | 1.02 (0.49 to 2.17) | |
| No | 54 (38.0) | 188 (34.2) | 2.61 (0.92 to 7.40) | 2.44 (1.12 to 5.35) | |
| Prolonged rupture of membranes ** | No | 108 (76.1) | 503 (91.5) | 1.00 | 1.00 |
| Unknown | 22 (15.5) | 36 (6.5) | 1.11 (0.37 to 3.33) | 1.08 (0.46 to 2.52) | |
| Yes | 12 (8.5) | 11 (2.0) | 8.85 (1.67 to 46.74) | 5.79 (1.73 to 19.34) | |
| Gestation (per week) | 0.82 (0.71 to 0.95) | 0.78 (0.70 to 0.87) | |||
| Feeding†† | Breastmilk | 65 (45.8) | 432 (78.5) | 1.00 | 1.00 |
| Unknown | 10 (7.0) | 10 (1.8) | 5.62 (1.20 to 26.21) | 3.94 (1.15 to 13.47) | |
| Formula | 36 (25.4) | 49 (8.9) | 4.99 (1.83 to 13.62) | 3.89 (1.97 to 7.71) | |
| Both | 31 (21.8) | 59 (10.7) | 5.98 (2.25 to 15.86) | 5.02 (2.45 to 10.26) | |
| Notification‡‡ | No | 78 (54.9) | 494 (89.8) | 1.00 | 1.00 |
| Yes | 64 (45.1) | 56 (10.2) | 6.37 (2.31 to 17.55) | 4.84 (2.61 to 8.97) |
*Ethnicity. Participant-defined. If multiple, prioritised as Māori, Pacific, Asian, Other, European.
†Other social history. Any social concern documented in clinical notes. Examples: attempted suicide, child in care, child protective services involved, partner in jail, prostitution, single parent, social worker involved.
‡De facto. Living together as a couple but not married.
§Unknowns in substance abuse history, other social history, partner status and booking.
¶Supplements. Any medication not usually prescribed, for example, folate, vitamins, iron (if not prescribed for anaemia).
**Membrane rupture more than 48 hours before delivery.
††Pattern of feeding in 24 hours before discharge. Breast includes expressing.
‡‡Any prior notification for a family member to the statutory child protective services agency.