Table 1.
Pregnancy-associated listeriosis 1997 to 2016, characteristics and incidence
| Characteristic of mother | Total casesn (%) | Women giving birth (× 1000) b | Incidence per 100,000 (95% CI) | IRR (95% CI) | p value |
|---|---|---|---|---|---|
| Age (n = 147) | |||||
| 15 to 19 | 7 (4.8) | 81 | 8.7 (4.2, 17.9) | 1 | 0.16 |
| 20 to 24 | 22 (15.0) | 214 | 10.3 (6.8, 15.6) | 1.19 (0.53, 3.00) | 0.69 |
| 25 to 29 | 39 (26.5) | 312 | 12.5 (9.1, 17.1) | 1.44 (0.69, 3.53) | 0.37 |
| 30 to 34 | 35 (23.8) | 352 | 9.9 (7.2, 13.8) | 1.15 (0.54, 2.82) | 0.74 |
| 35 to 39 | 26 (17.7) | 196 | 13.3 (9.1, 19.5) | 1.53 (0.70, 3.83) | 0.32 |
| 40 to 45 | 11 (7.5) | 43 | 25.6 (14.3, 45.8) | 2.95 (1.16, 8.02) | 0.025 |
| Unknown | 7 | ||||
| Prioritised ethnicity (n = 115) a | |||||
| European or other | 44 (29.9) | 511 | 8.6 (6.4, 11.6) | 1 | < 0.001 |
| Māori | 17 (11.6) | 240 | 7.1 (4.4, 11.3) | 0.82 (0.46, 1.41) | 0.49 |
| Pacific | 33 (22.4) | 108 | 30.6 (21.8, 43.0) | 3.56 (2.25, 5.57) | < 0.001 |
| Asian | 21 (14.3) | 106 | 19.7 (12.9, 30.2) | 2.29 (1.34, 3.81) | 0.002 |
| Unknown | 0 | ||||
| Overall | 147 | 1197 | 12.3 (10.4, 14.4) | ||
P values in italics represent overall likelihood ratio test for the age or ethnicity. All other p values represent Wald pairwise comparisons with reference group
aEthnicity is prioritised in the order Maori, Pacific, Asian, European or other. Comparisons by ethnicity are restricted to years 2001 to 2016 due to availability of denominator data
bBirths as recorded in the NZ MoH Maternity Collection
IRR Incidence rate ratio