Table 2.
Comparison of perinatal outcomes in the exposed and comparison populations: risks (%) and adjusted relative risks (RR) of adverse perinatal outcomes, and means and adjusted difference in means of growth measurements.
| NT | Qld | NSW | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Exposed % (n) |
Comparison % (n) | Adjusted RR 1 (95% CI) |
Adjusted RR 2 (95% CI) |
Exposed % (n) |
Comparison % (n) | Adjusted RR 1 (95% CI) |
Adjusted RR 2 (95% CI) |
Exposed % (n) |
Comparison % (n) | Adjusted RR 1 (95% CI) |
Adjusted RR 2 (95% CI) |
|
| Adverse Perinatal Outcome | ||||||||||||
| Total sample | 5606 | 11,364 | 665 | 3989 | 188 | 7287 | ||||||
| Gestational diabetes 3 | 7% (215) | 7% (505) | 1.08 (0.92,1.28) | 1.11 (0.94,1.32) | 8% (53) | 9% (361) | 0.95 (0.71,1.27) | 0.88 (0.66,1.19) | 8% (13) | 5% (306) | 1.44 (0.85,2.44) | 1.42 (0.84,2.41) |
| Pregnancy-induced hypertension | 5% (294) | 5% (607) | 0.93 (0.80,1.07) | 1.10 (0.92,1.32) | 3% (17) | 2% (99) | 1.03 (0.62,1.72) | 0.94 (0.56,1.59) | 16% (30) | 7% (527) | 2.00 (1.36,2.93) | 1.88 (1.30,2.73) |
| Caesarean/assisted vaginal | 31% (1711) | 34% (3853) | 0.99 (0.95,1.05) | 0.97 (0.91,1.03) | 40% (263) | 36% (1427) | 1.13 (1.01,1.27) | 1.12 (1.00,1.25) | 38% (71) | 33% (2423) | 1.03 (0.84,1.26) | 0.98 (0.81,1.20) |
| Emergency caesarean | 11% (607) | 12% (1306) | 1.00 (0.90,1.10) | 1.08 (0.96,1.21) | 14% (90) | 12% (490) | 1.10 (0.88,1.37) | 1.11 (0.89,1.39) | 13% (25) | 10% (747) | 1.22 (0.83,1.81) | 1.12 (0.76,1.65) |
| Postpartum haemorrhage ⁴ | 8% (475) | 9% (1075) | 0.96 (0.86,1.06) | 1.01 (0.90,1.14) | 6% (43) | 7% (265) | 0.96 (0.70,1.32) | 0.89 (0.63,1.26) | 34% (10) | 19% (174) | 1.97 (1.14,3.38) | 1.94 (1.13,3.33) |
| Preterm birth | 8% (455) | 8% (929) | 0.95 (0.85,1.07) | 1.06 (0.92,1.22) | 9% (61) | 8% (314) | 1.13 (0.85,1.49) | 1.04 (0.77,1.41) | 8% (15) | 5% (399) | 1.46 (0.89,2.39) | 1.47 (0.90,2.40) |
| Spontaneous preterm birth | 6% (310) | 5% (586) | 0.99 (0.86,1.14) | 1.14 (0.96,1.36) | 4% (29) | 5% (180) | 0.97 (0.65,1.44) | 0.90 (0.58,1.39) | 4% (7) | 3% (234) | 1.27 (0.60,2.68) | 1.32 (0.63,2.77) |
| Small for gestational age (SGA) | 13% (750) | 14% (1553) | 0.87 (0.79,0.94) | 0.92 (0.82,1.03) | 5% (30) | 5% (192) | 0.93 (0.63,1.37) | 1.02 (0.69,1.51) | 7% (13) | 9% (621) | 0.87 (0.48,1.57) | 0.86 (0.48,1.53) |
| Large for gestational age (LGA) | 8% (453) | 9% (1028) | 0.96 (0.86,1.08) | 0.91 (0.80,1.04) | 6% (39) | 6% (259) | 0.93 (0.66,1.32) | 0.89 (0.63,1.27) | 11% (20) | 11% (836) | 0.89 (0.58,1.37) | 0.95 (0.62,1.45) |
| Stillbirth | 1% (45) | 1% (89) | 0.94 (0.66,1.35) | 0.90 (0.54,1.50) | 2% (11) | 1% (27) | 2.43 (1.20,4.93) | 2.59 (1.25,5.39) | (≤5) | <1% (34) | 1.13 (0.15,8.29) | 1.17 (0.16,8.61) |
| Low Apgar score at 5 min | 3% (164) | 3% (327) | 0.93 (0.77,1.13) | 1.07 (0.83,1.37) | 4% (29) | 3% (113) | 1.50 (0.99,2.26) | 1.47 (0.95,2.26) | (≤5) | 2% (161) | 0.98 (0.37,2.57) | 0.95 (0.36,2.51) |
| Term (≥37 weeks) outcome | ||||||||||||
| Total sample | 5125 | 10,346 | 604 | 3674 | 173 | 6885 | ||||||
| Term low Apgar score at 5 min | 2% (80) | 2% (185) | 0.77 (0.59,1.00) | 0.84 (0.59,1.20) | 2% (14) | 2% (70) | 1.15 (0.66,2.00) | 1.21 (0.69,2.10) | (≤5) | 2% (103) |
1.57 (0.58,4.20) | 1.51 (0.56,4.07) |
| Exposed mean (SD) | Comparison mean (SD) | Adjusted difference in means 1 (95% CI) | Adjusted difference in means 2 (95% CI) | Exposed mean (SD) | Comparison mean (SD) | Adjusted difference in means 1 (95% CI) | Adjusted difference in means 2 (95% CI) | Exposed mean (SD) | Comparison mean (SD) | Adjusted difference in means 1 (95% CI) | Adjusted difference in means 2 (95% CI) | |
| Growth measure | ||||||||||||
| Total sample | 5125 | 10,346 | 604 | 3674 | 173 | 6885 | ||||||
| Term birth weight (g) | 3423 (488.9) | 3405 (488.9) | 31.1 (14.4,47.9) | 11.22 (−8.9,31.3) |
3465 (448.8) | 3483 (468.9) |
−9.6 (−49.7,30.6) |
−11.1 (−48.7,26.5) |
3519 (479.6) | 3515 (477.4) | 21.7 (−49.0,92.1) |
35.7 (−29.4,100.8) |
| Term birth length (cm) ⁵ | 50.7 (2.7) |
50.3 (2.4) |
0.3 (0.1,0.4) |
0.2 (0.1,0.4) | 51.6 (2.6) |
51.4 (2.6) |
0.3 (0.1,0.5) | 0.3 (0.1,0.5) |
Data not available | |||
| Term head circumference (cm) ⁶ | 34.7 (1.7) |
34.6 (1.5) |
0.1 (0.0,0.2) |
0.0 (−0.1,0.1) |
34.7 (1.6) |
34.7 (1.5) |
0.0 (−0.1,0.2) |
0.0 (−0.1,0.2) |
||||
Notes: The RR is the risk in the exposed group divided by the risk in the comparison group. The difference in means is the mean in the exposed group minus the mean in the comparison group. 1 RRs/Difference in means from Model 1: adjusted for year of birth, maternal age, and mother’s Aboriginal and Torres Strait Islander status (except NSW). Outcomes restricted to term babies included adjustment for gestational week. 2 RRs/Difference in means from Model 2: adjusted for year of birth, maternal age, maternal Aboriginal and Torres Strait Islander status (except NSW), parity, marital status (except NSW), maternal country of birth, maternal BMI (Qld only), and maternal ever smoked during pregnancy. Caesarean/assisted vaginal, emergency caesarean and postpartum haemorrhage were additionally adjusted for macrosomia. Preterm birth, stillbirth, low Apgar, and growth measures were additionally adjusted for the sex of the baby. Outcomes restricted to term babies included adjustment for gestational week. RRs from Model 2 are represented in a forest plot in Figure 1. 3 Gestational diabetes is only available in the NSW Perinatal Data Collection (PDC) from 1994 to 2015; the denominators for exposed and comparison are 159 and 6345, respectively. Gestational diabetes is only available in the NT PDC from 2000; the denominators for exposed and comparison are 2943 and 7229, respectively. 4 Postpartum haemorrhage is only available in the NSW PDC from 2016; the denominators for exposed and comparison are 29 and 938, respectively. For this outcome, year was modelled as a categorical rather than continuous covariate. 5 Birth length is only available in the NT PDC from 2008; the denominators for exposed and comparison are 1422 and 3024, respectively. 6 Head circumference is only available in the NT PDC from 2008; the denominators for exposed and comparison are 1391 and 2954, respectively.