Figures (0)  Tables (3)
    • Variables Gestation 0–5 years
      Unexposed (%) Exposed (%) Total (%) Unexposed (%) Unexposed (%) Total (%)
      Sample size 222,099 93,687 315,789 11,718 303,846 315,567
      Sex Male 114,216 (51.4) 48,351 (51.6) 162,567 (51.5) 5,607 (47.9) 15,6843 (51.6) 162,450 (51.5)
      Female 107,883 (48.6) 45,339 (48.4) 153,219 (48.5) 6,108 (52.1) 147,003 (48.4) 153,111 (48.5)
      Ethnicity NZ Europeans 108,834 (49) 35,475 (37.9) 144,309 (45.7) 6,255 (53.4) 137,904 (45.4) 144,156 (45.7)
      Māori 62,733 (28.3) 35,811 (38.2) 98,544 (31.2) 2,478 (21.3) 96,021 (31.6) 98,499 (31.2)
      Pacifica 21,036 (9.5) 12,981 (13.9) 34,017 (10.8) 921 (7.9) 33,084 (10.9) 34,005 (10.8)
      Asian 23,271 (10.5) 7,272 (7.8) 30,543 (9.7) 1,641 (14) 28,893 (9.5) 30,534 (9.7)
      Middle Eastern, Latin American, and African (MELAA) 2,724 (1.2) 1,095 (1.2) 3,816 (1.2) 228 (1.9) 3,588 (1.2) 3,813 (1.2)
      Others 3,501 (1.6) 1,059 (1.1) 4,563 (1.4) 195 (1.7) 4,359 (1.4) 4,557 (1.4)
      Deprivation Index deciles 10 (most deprived) 30,360 (13.7) 20,352 (21.7) 50,712 (16.1) 1,134 (9.7) 49,563 (16.3) 50,694 (16.1)
      9 24,813 (11.2) 13,494 (14.4) 38,304 (12.1) 1,140 (9.7) 37,137 (12.2) 38,274 (12.1)
      8 22,224 (10) 10,569 (11.3) 32,793 (10.4) 1,083 (9.2) 31,680 (10.4) 32,763 (10.4)
      7 21,483 (9.7) 9,009 (9.6) 30,492 (9.7) 1,122 (9.6) 29,352 (9.7) 30,474 (9.7)
      6 20,340 (9.2) 7,617 (8.1) 27,957 (8.9) 1,020 (8.7) 26,910 (8.9) 27,930 (8.9)
      5 19,716 (8.9) 6,750 (7.2) 26,466 (8.4) 1,137 (9.7) 25,305 (8.3) 26,439 (8.4)
      4 18,810 (8.5) 6,177 (6.6) 24,993 (7.9) 1,053 (9.0) 23,919 (7.9) 24,975 (7.9)
      3 17,601 (7.9) 5,226 (5.6) 22,830 (7.2) 981 (8.4) 21,828 (7.2) 22,806 (7.2)
      2 16,527 (7.4) 4,704 (5.0) 21,231 (6.7) 1,011 (8.6) 20,205 (6.7) 21,216 (6.7)
      1 (least deprived) 13,623 (6.1) 3,786 (4.0) 17,409 (5.5) 774 (6.6) 16,623 (5.5) 17,394 (5.5)
      Rurality Urban 171,879 (77.4) 73,761 (78.7) 245,640 (77.8) 8,436 (72.0) 237,039 (78.0) 245,475 (77.8)
      Rural 33,642 (15.2) 13,926 (14.9) 47,568 (15.1) 2,019 (17.2) 45,504 (14.9) 47,526 (15.1)
      Missing 16,581 (7.5) 6,000 (6.4) 22,581 (7.2) 1,263 (10.8) 21,303 (7.0) 22,566 (7.2)
      Birthweight Low birth weight (LBW) (< 2,500 g) 11,475 (5.2) 6,774 (7.2) 18,249 (5.8) 642 (5.5) 17,595 (5.8) 18,237 (5.8)
      Normal birth weight (NBW) (2,500–4,000 g) 174,972 (78.8) 72,816 (77.7) 247,785 (78.5) 9,225 (78.7) 238,380 (78.5) 247,605 (78.5)
      High birth weight (HBW) (> 4,000 g) 34,863 (15.7) 13,809 (14.7) 48,672 (15.4) 1,764 (15.1) 46,881 (15.4) 48,642 (15.4)
      Type of delivery Caesarean section (elective) 22,512 (10.1) 10,539 (11.3) 33,051 (10.5) 1,119 (9.6) 31,908 (10.5) 33,027 (10.5)
      Caesarean section (emergency) 29,934 (13.5) 12,711 (13.6) 42,645 (13.5) 1,296 (11.1) 41,316 (13.6) 42,612 (13.5)
      Non-caesarean section 162,555 (73.2) 67,560 (72.1) 230,118 (72.9) 8,049 (68.7) 221,904 (73.0) 229,953 (72.8)
      Missing 6,765 (3.1) 2,748 (2.9) 9,513 (3.0) 1,242 (10.6) 8,262 (2.7) 9,507 (3.0)
      Gestational age Full-term
      (37 weeks ≤ gestational age < 40 weeks)      		 119,202 (53.7) 48,363 (51.6) 167,568 (53.1) 6,318 (53.9) 161,145 (53.0) 167,463 (53.1)
      Pre-term (gestational age < 37 weeks) 52,644 (23.7) 27,288 (29.1) 79,932 (25.3) 2,685 (22.1) 77,175 (25.4) 79,857 (25.3)
      Late-term
      (41 weeks ≤ gestational age < 42 weeks)      		 40,989 (18.5) 14,703 (15.7) 55,689 (17.6) 2,163 (18.5) 53,493 (17.6) 55,653 (17.6)
      Post-term (≥ 42 weeks) 9,141 (4.1) 3,300 (3.5) 12,444 (3.9) 495 (4.2) 11,943 (3.9) 12,438 (3.9)
      Maternal age at delivery (years) < 25 45,039 (20.3) 30,030 (32.1) 75,069 (23.8) 1,935 (16.5) 73,089 (24.1) 75,027 (23.8)
      < 30 52,344 (23.6) 22,077 (23.6) 74,418 (23.6) 2,754 (23.5) 71,613 (23.6) 74,364 (23.6)
      < 35 67,329 (30.3) 22,221 (23.7) 89,553 (28.4) 3,585 (30.6) 85,911 (28.3) 89,496 (28.4)
      ≥ 35 57,375 (25.8) 19,359 (20.7) 76,734 (24.3) 3,447 (29.4) 73,221 (24.1) 76,668 (24.3)
      Counts are randomly rounded to comply with Statistics New Zealand’s data privacy requirements; as a result, totals may be slightly different across different variables and analyses.

      Table 1. 

      Characteristics of the study population for children born in New Zealand between 1 October 2005 and 30 December 2010 stratified by antibiotic exposure status during gestation and ages 0–5 years (exposed vs unexposed).

    • Exposure T1D cases Population size Algorithm 1*:
      Prescription claims and hospitalisation
      HR (95% CI) for T1D unadjusted HRa (95% CI) for T1D, adjusted for all variables
      Antibiotics courses (continuous variable) 1,131 315,789 1.06 (1.03–1.08) 1.05 (1.03–1.08)
      Antibiotics during pregnancy No 777 222,099 Ref Ref
      Yes 354 93,687 1.18 (1.04–1.33) 1.20 (1.05–1.38)
      Antibiotics courses during pregnancy 0 780 222,102 Ref Ref
      1 219 59,361 1.13 (0.97–1.32) 1.17 (1.00–1.37)
      2 66 21,438 0.96 (0.74–1.23) 1.02 (0.78–1.32)
      ≥ 3 72 12,888 1.73 (1.36–2.21) 1.85 (1.44–2.38)
      Test for trend 0.0008
      Antibiotics during pregnancy by type (class), ever user vs never any Penicillin 282 76,413 1.13 (0.99–1.30) 1.16 (1.01–1.34)
      Other antibiotics 21 5,316 1.06 (0.67–1.67) 1.00 (0.62–1.60)
      Macrolides 66 16,476 1.17 (0.91–1.50) 1.18 (0.91–1.53)
      Cephalosporins and cephamycins 48 9,756 1.46 (1.09–1.95) 1.42 (1.05–1.92)
      Tetracyclines 9 1,245 1.85 (0.92–3.71) 1.81 (0.90–3.65)
      Antibiotic use by spectrum (ever vs never) Narrow 84 25,749 0.95 (0.76–1.18) 1.07 (0.85–1.34)
      Moderate 42 8,904 1.49 (1.10–2.03) 1.57 (1.13–2.18)
      Broad 240 60,681 1.22 (1.06 – 1.40) 1.30 (1.12–1.51)
      a HRs were adjusted for: sex, ethnicity, NZ deprivation index, rurality, maternal age at delivery, gestational age and mode of obstetric delivery. * Results are presented based on the first algorithm used for identifying T1D cases. See Supplementary Table S2 for detailed descriptions of the algorithms. Note: counts are randomly rounded to comply with Statistics New Zealand’s data privacy requirements; as a result, totals may be slightly different across different variables and analyses.

      Table 2. 

      Association between antibiotic use during pregnancy and T1D in childhood.

    • Exposure T1D cases Population size Algorithm 1: Prescription claims and hospitalisation
      HR (95% CI) for T1D unadjusted HRa (95% CI) for T1D, adjusted for all variables
      Antibiotics courses (continuous variable) 906 315,564 1.02 (1.02–1.03) 1.02 (1.02–1.03)
      Antibiotic use No 18 11,718 Ref Ref
      Yes 891 303,849 1.71 (1.08–2.73) 1.62 (1.00–2.63)
      Antibiotic courses 0 18 11,718 Ref Ref
      1–4 255 96,078 1.54 (0.96–2.49) 1.45 (0.88–2.37)
      5–7 183 63,771 1.68 (1.04–2.73) 1.61 (0.97–2.65)
      8–12 201 69,375 1.69 (1.04–2.73) 1.60 (0.97–2.63)
      ≥ 13 255 74,625 1.99 (1.23–3.21) 1.93 (1.18–3.17)
      Test for trend 0.0017
      Antibiotic use by type (class), ever user vs never any Penicillin 876 297,540 1.72 (1.08–2.75) 1.63 (1.01–2.64)
      Other antibiotics 363 113,175 1.86 (1.16–2.99) 1.72 (1.05–2.81)
      Macrolides 336 106,341 1.88 (1.17–3.02) 1.86 (1.14–3.04)
      Cephalosporins and cephamycins 300 94,869 1.92 (1.19–3.09) 1.83 (1.12–3.00)
      Tetracyclines S S S S
      Antibiotic use by type (class), only user vs never any Penicillin 261 104,520 1.44 (0.89–2.32) 1.36 (0.83–2.23)
      Other antibiotics S S S S
      Macrolides 9 1,896 2.30 (0.96–5.50) 1.55 (0.27–4.24)
      Cephalosporins and cephamycins S S S S
      Tetracyclines S S S S
      Antibiotic use by spectrum (ever vs never any) Narrow 675 226,215 1.15 (0.99–1.33) 1.17 (1.01–1.38)
      Moderate 300 94,863 1.22 (1.06–1.40) 1.23 (1.07–1.42)
      Broad 888 301,995 1.72 (1.11–2.65) 1.74 (1.10–2.78)
      Antibiotics (counts) stratified by mode of delivery Caesarean section (elective) 126 33,027 1.03 (1.01–1.04) 1.02 (1.01–1.04)
      Caesarean section (emergency) 123 42,611 1.02 (1.00–1.03) 1.01 (0.99–1.03)
      Non-caesarean section 639 229,952 1.02 (1.02–1.03) 1.03 (1.02–1.03)
      a HRs were adjusted for all variables: sex, ethnicity, NZ deprivation index, rurality, maternal age at delivery, gestational age, mode of obstetric delivery, and birth weight. *Results are presented based on the first algorithm used for identifying T1D cases. See Supplementary Table S2 for detailed descriptions of the algorithms. S: All counts under six and the HRs derived from these are suppressed according to IDI confidentiality requirements. Note: Counts are randomly rounded to comply with Statistics New Zealand’s data privacy requirements; as a result, totals may be slightly different across different variables and analyses.

      Table 3. 

      Associations between antibiotic use in the first 5 years and subsequent T1D after age 5.