Table 2.
Primary and secondary outcomes for all pregnancies in the pre-pandemic, exposure 1 and 2 cohorts
| Outcomes | Pre-pandemic n = 1219 | Exposure 1 n = 433 | Exposure 2 n = 615 | Exposure 1 aRR | Exposure 2 aRR | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| n | % | n | % | n | 27% | aRRa | 95% CI | P value | aRRa | 95% CI | P value | |
| Preterm birth < 37 wk | ||||||||||||
| Total | 833 | 68.3 | 273 | 63.1 | 438 | 71.2 | 0.92 | 0.87–0.98 | 0.01 | 1.03 | 0.98–1.09 | 0.19 |
| Spontaneous | 247 | 20.3 | 82 | 18.9 | 136 | 22.1 | 0.95 | 0.90–0.99 | 0.04 | 1.00 | 0.95–1.04 | 0.83 |
| Iatrogenic | 586 | 48.1 | 191 | 44.1 | 302 | 49.1 | 0.97 | 0.92–1.03 | 0.39 | 1.04 | 0.99–1.10 | 0.16 |
| Preterm birth < 34 wk | ||||||||||||
| Total | 280 | 23.0 | 86 | 19.9 | 168 | 27.3 | 0.93 | 0.89–0.98 | 0.01 | 1.04 | 0.99–1.09 | 0.09 |
| Spontaneous | 129 | 10.6 | 45 | 10.4 | 72 | 11.7 | 0.97 | 0.94–1.01 | 0.15 | 1.01 | 0.98–1.04 | 0.65 |
| Iatrogenic | 151 | 12.4 | 41 | 9.5 | 96 | 15.6 | 0.96 | 0.92–1.00 | 0.05 | 1.03 | 1.00–1.07 | 0.09 |
| Preterm birth < 28 wk | ||||||||||||
| Total | 58 | 4.8 | 23 | 5.3 | 44 | 7.2 | 1.00 | 0.97–1.03 | 0.95 | 1.03 | 1.01–1.05 | 0.04 |
| Spontaneous | 30 | 2.5 | 12 | 2.8 | 22 | 3.6 | 1.00 | 0.98–1.02 | 0.79 | 1.02 | 1.00–1.03 | 0.09 |
| Iatrogenic | 28 | 2.3 | 11 | 2.5 | 22 | 3.6 | 0.98 | 0.96–1.00 | 0.08 | 1.00 | 0.98–1.02 | 0.94 |
| Preterm birth < 24 wk | ||||||||||||
| Total | 20 | 1.6 | 7 | 1.6 | 15 | 2.4 | 0.99 | 0.97–1.00 | 0.10 | 1.00 | 0.98–1.01 | 0.64 |
| Iatrogenic | 12 | 1.0 | 6 | 1.4 | 8 | 1.3 | 1.00 | 0.98–1.01 | 0.44 | 1.00 | 0.99–1.01 | 0.47 |
| Spontaneous | 8 | 0.7 | 1 | 0.2 | 7 | 0.8 | 0.99 | 0.98–1.00 | 0.10 | 1.00 | 0.99–1.01 | 0.88 |
| Iatrogenic birth for suspected fetal compromise | ||||||||||||
| Total | 249 | 0.4 | 58 | 13.4 | 122 | 19.8 | 0.94 | 0.89–0.98 | 0.01 | 1.00 | 0.96–1.04 | 0.92 |
| ≥ 37 wk | 53 | 13.7 | 11 | 6.9 | 27 | 15.3 | 0.94 | 0.88–1.01 | 0.07 | 1.02 | 0.96–1.09 | 0.54 |
| < 37 wk | 196 | 23.5 | 47 | 17.2 | 95 | 21.7 | 0.94 | 0.89–1.01 | 0.08 | 0.99 | 0.94–1.04 | 0.61 |
| Mode of birth | ||||||||||||
| Vaginal | 361 | 29.6 | 112 | 25.9 | 180 | 29.3 | 0.93 | 0.88–0.98 | 0.01 | 0.96 | 0.92–1.01 | 0.12 |
| Cesarean section after labor onset | 413 | 33.9 | 145 | 33.5 | 235 | 38.2 | 0.97 | 0.92–1.03 | 0.30 | 1.03 | 0.98–1.08 | 0.32 |
| Cesarean section with no labor | 445 | 36.5 | 176 | 40.6 | 200 | 32.5 | 1.11 | 1.05–1.18 | 0.001 | 1.01 | 0.96–1.06 | 0.66 |
| Pregnancy care indicators | ||||||||||||
| First antenatal visit ≤ 12 wk | 717 | 58.8 | 294 | 67.9 | 426 | 69.3 | 1.06 | 1.00–1.12 | 0.05 | 1.06 | 1.01–1.12 | 0.02 |
| Severe PPH > 1000ml | 129 | 10.6 | 40 | 9.2 | 66 | 10.7 | 0.96 | 0.92–0.99 | 0.02 | 0.98 | 0.95–1.01 | 0.23 |
aRR Adjusted risk ratio, CI Confidence interval, PPH Post-partum haemorrhage, wk Weeks
aAdjusted for covariates of preterm birth including maternal age group, first measured BMI, region of birth, SEIFA, interpreter requirement, parity, smoking status and pertussis vaccination using multivariate log-binomial regression models. The log-binomial regression models used the ‘multiple imputations by chained equation’ (MICE) to account for missing data: missing or implausible for weight = 85 (3.76%); missing or implausible height = 15 (0.66%), smoking status = 0 (0%), need for interpreter variable = 0 (0%), maternal age = 6 (0.13%), BMI = 169 (7.34%), region of birth = 11 (0.49%), SEIFA = 35 (1.55%), sex = 1 (0.04%)