Table 1.
Comparison of maternal and pregnancy characteristics among the pre-pandemic, exposure 1 and exposure 2 groups
| Maternal characteristics | Pre-pandemic | Exposure 1 | Exposure 2 | P value |
|---|---|---|---|---|
| n = 1219 | n = 433 | n = 615 | ||
| Maternal age in years, mean (SD) | 32.72 (5.2) | 32.45 (4.6) | 32.27 (4.9) | 0.18 |
| Weight in kg, mean (SD) | 72.04 (21.2) | 69.78 (23.8) | 70.84 (22.6) | 0.17 |
| Height in cm, mean (SD) | 160.80 (24.1) | 157.23 (33.0) | 158.78 (30.3) | 0.05 |
| Smoking in pregnancy, n (%) | 58 (6.3) | 33 (10.1) | 26 (5.8) | 0.04 |
| Interpreter required, n (%) | 47 (3.9) | 15 (3.5) | 22 (3.6) | 0.92 |
| Pertussis vaccination during pregnancy, n (%) | 997 (85.6) | 308 (72.1) | 450 (74.5) | < 0.001 |
| Influenza vaccination during pregnancy, n (%) | 887 (75.9) | 302 (70.2) | 367 (61.0) | < 0.001 |
| > 1 COVID-19 vaccine dose before or during pregnancy, n/N (%)a | - | - | 197/358a (55.0) | NA |
| COVID-19 infection during pregnancy | - | 0 (0.0) | 5 (0.8) | 0.001 |
| < 37 wk | - | 0 (0.0) | 2 (40.0) | |
| < 34 wk | - | 0 (0.0) | 1 (20.0) | |
| < 32 wk | - | 0 (0.0) | 2 (40.0) | |
| < 28 wk | - | 0 (0.0) | 0 (0.0) | |
| Maternal age group in years, n (% of total) | ||||
| 18–24 | 107 (8.8) | 40 (9.2) | 69 (11.3) | 0.33 |
| 25–29 | 247 (20.3) | 84 (19.4) | 119 (19.4) | |
| 30–34 | 490 (40.2) | 185 (42.7) | 247 (40.4) | |
| 35–39 | 280 (23.0) | 103 (23.8) | 143 (23.4) | |
| ≥ 40 | 95 (7.8) | 21 (4.9) | 34 (5.6) | |
| BMI categories in Kg/m2, n (% of total) | ||||
| < 18 | 13 (1.1) | 2 (0.5) | 3 (0.6) | 0.67 |
| 18 – 24 | 476 (40.6) | 169 (42.4) | 234 (44.0) | |
| 25 – 29 | 370 (31.5) | 115 (28.8) | 146 (27.4) | |
| 30 – 34 | 176 (15.0) | 63 (15.8) | 92 (17.3) | |
| 35 – 39 | 83 (7.1) | 32 (8.0) | 35 (6.6) | |
| ≥ 40 | 56 (4.8) | 18 (4.5) | 22 (4.1) | |
| Region of birth, n (% of total pregnancies) | ||||
| Americas | 17 (1.4) | 9 (2.1) | 19 (3.1) | 0.52 |
| Australia and Associated Territories | 728 (59.8) | 254 (59.4) | 354 (58.0) | |
| North Africa and Middle East | 64 (5.3) | 15 (3.5) | 28 (4.6) | |
| North East Asia | 35 (2.9) | 12 (2.8) | 16 (2.6) | |
| North West Europe | 38 (3.1) | 21 (4.9) | 18 (3.0) | |
| Oceania | 46 (3.8) | 15 (3.5) | 19 (3.1) | |
| South East Asia | 59 (4.8) | 22 (5.1) | 28 (4.6) | |
| Southern and Central Asia | 167 (13.7) | 60 (14.0) | 96 (15.9) | |
| Southern and Eastern Europe | 18 (1.5) | 6 (1.4) | 14 (2.3) | |
| Sub-Saharan Africa | 46 (3.8) | 14 (3.3) | 17 (2.8) | |
| Parity, n (%) | ||||
| 0 | 569 (46.8) | 197 (45.5) | 293 (47.6) | 0.79 |
| ≥ 1 | 648 (53.3) | 236 (54.5) | 322 (52.4) | |
| SEIFA quintile, n (%) | ||||
| 1 – Most disadvantaged | 240 (19.7) | 89 (20.6) | 137 (22.3) | 0.18 |
| 2 | 207 (17.0) | 58 (13.4) | 83 (13.5) | |
| 3 | 306 (25.1) | 101 (23.3) | 153 (24.9) | |
| 4 | 279 (22.9) | 97 (22.4) | 140 (22.8) | |
| 5 – Most advantaged | 185 (15.2) | 88 (20.3) | 102 (16.6) | |
| Pregnancy characteristics, n (%) | ||||
| Sex-concordant | 829 (68.0) | 302 (69.8) | 448 (72.9) | 0.11 |
| Sex-discordant | 389 (32.0) | 131 (30.3) | 167 (27.2) | |
BMI Body mass index, SD Standard deviation, SEIFA Socioeconomic index for areas
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%)
aThe denominator for COVID-19 vaccination status is lower than total women in the exposure 2 group as vaccination status was only available from 1 July 2021