Sociodemographic, lifestyle and clinical characteristics of term and preterm deliveries, spontaneous and electives
| All women (N=38 528)* | Term deliveries† (n=37 167) | PTD‡ (n=2361) | OR (95% CI)§ | sPTD (n=1075) | ePTD (n=1286) | p Value | |
| Demographic characteristics | |||||||
| Maternal age | |||||||
| <35 years old | 28655(72.5) | 27 034 (72.7) | 1621 (68.7) | 1.0 | 810 (75.3) | 811 (63.1) | <0.001* |
| ≥35 years old | 10873 (27.5) | 10133 (27.3) | 740 (31.3) | 1.2 (1.1 to 1.3) | 265 (24.7) | 475 (36.9) | |
| Nativity | |||||||
| European | 33812 812 (86.0) | 31857 (86.0) | 2033 (86.6) | 1.0 | 926 (87.1) | 1107 (86.3) | 0.583 |
| Non-European | 5499 (14.0) | 5168 (14.0) | 313 (13.3) | 1.1 (1.0 to 1.2) | 137 (12.9) | 176 (13.7) | |
| Nationality | |||||||
| Irish | 27657(70.3) | 26003 (70.2) | 1654 (71.8) | 1.0 (0.9 to 1.1) | 735 (69.9) | 919 (73.4) | 0.063 |
| Non-Irish | 11672 (29.7) | 11022 (29.8) | 650 (28.2) | 1.0 | 317 (30.1) | 333 (26.6) | |
| Occupation | |||||||
| Employed | 36988 (94.2) | 32236 (87.2) | 1903 (82.9) | 1.0 | 849 (81.2) | 1054 (84.3) | 0.058 |
| Unemployed | 2295 (5.8) | 4752 (12.8) | 392 (17.1) | 1.4 (1.2 to 1.5) | 196 (18.8) | 196 (15.7) | |
| BMI at first prenatal visit, mean (SD) | 25.5 (5.5) | 25.5 (5.0) | 25.9 (5.4) | <0.001* | 24.0 (22.0–28.0) | 26.0 (23.0–30.0) | <0.001* |
| Lifestyle characteristics | |||||||
| Smoking status | |||||||
| Current smoker | 5880 (14.9) | 5390 (14.5) | 490 (20.8) | 1.4 (1.3 to 1.6) | 283 (26.3) | 207 (16.1) | |
| Former smoker | 12612 (31.9) | 11961 (32.2) | 651 (27.6) | 0.8 (0.8 to 0.9) | 276 (25.7) | 375 (29.2) | <0.001* |
| Never smoke | 21036 (53.2) | 19816 (53.3) | 1220 (51.7) | 1.0 | 516 (48.0) | 704 (54.7) | |
| Alcohol consumption | |||||||
| >10 units/week | 15 (0.0004) | 10 (0.03) | 5 (0.23) | 1.3 (0.9 to 1.9) | 4 (0.4) | 1 (0.1) | 0.269 |
| 1–10 units/week | 652 (1.8) | 623 (1.8) | 29 (1.4) | 0.1 (0.04 to 0.3) | 12 (1.2) | 17 (1.4) | |
| No alcohol | 36447 (98.2) | 34335 (98.2) | 2112 (98.4) | 1.0 | 950 (98.3) | 1162 (98.5) | |
| Illicit drugs | |||||||
| Yes | 2944 (7.5) | 2705 (7.3) | 239 (10.5) | 1.4 (1.2 to 1.7) | 140 (13.6) | 99 (7.9) | |
| No | 36456 (92.5) | 34414 (92.7) | 2042 (89.5) | 1.0 | 891 (86.4) | 1151 (92.1) | <0.001* |
| Domestic violence | |||||||
| Yes | 431 (1.1) | 393 (1.1) | 38 (1.7) | 1.5 (1.1 to 2.2) | 15 (1.5) | 23 (1.8) | 0.515 |
| No | 38865 (98.9) | 36635 (98.9) | 2230 (98.3) | 1.0 | 1009 (98.5) | 1221 (98.2) | |
| Clinical characteristics | |||||||
| Parity | |||||||
| Nulliparous | 15699 (39.7) | 14633 (39.4) | 1066 (45.2) | 1.2 (1.1 to 1.3) | 495 (46.0) | 571 (44.4) | 0.430 |
| Multiparous | 23829 (60.3) | 22534 (60.6) | 1295 (54.8) | 1.0 | 580 (54.0) | 715 (55.6) | |
| Planned pregnancy | |||||||
| Yes | 27031 (68.7) | 25 566 (68.9) | 1465 (63.8) | 1.0 | 613 (58.8) | 852 (68.1) | <0.001* |
| No | 12344 (31.3) | 11514 (31.1) | 830 (36.2) | 1.2 (1.1 to 1.3) | 430 (41.2) | 400 (31.9) | |
| Treatment for infertility | |||||||
| Yes | 702 (1.8) | 578 (1.6) | 124 (5.3) | 2.8 (2.4 to 3.3) | 31 (2.9) | 93 (7.2) | <0.001* |
| No | 38826 (98.2) | 36589 (98.4) | 2237 (94.7) | 1.0 | 1044 (97.1) | 1193 (92.8) | |
| Type of pregnancy | |||||||
| Singletons | 38717 (97.9) | 36765 (98.9) | 1952 (82.7) | 1.0 | 942 (87.6) | 1010 (78.5) | <0.001* |
| Multiples | 811 (2.1) | 402 (1.1) | 409 (17.3) | 19.1 (16.5 to 22.1) | 133 (12.4) | 276 (21.5) | |
| Prenatal care attendance | |||||||
| Regular | 31530 (98.5) | 29797 (98.8) | 1733 (92.8) | 1.0 | 774 (91.1) | 959 (94.3) | |
| No attendance or irregular | 485 (1.5) | 351 (1.2) | 134 (7.2) | 6.5 (5.3 to 8.0) | 76 (8.9) | 58 (5.7) | 0.009* |
| Type of labour | |||||||
| Spontaneous | 21172 (53.6) | 20097 (54.1) | 1075 (45.5) | 1.0 | 1075 (100.0) | – | |
| No labour | 6612 (16.7) | 5638 (15.2) | 974 (41.3) | 3.2 (2.9 to 3.5) | – | 974 (75.7) | |
| Induction of labour | 11744 (29.7) | 11432 (30.8) | 312 (13.2) | 0.5 (0.4 to 0.6) | – | 312 (24.3) | |
| Mode of delivery | |||||||
| Spontaneous vaginal | 22946 (58.1) | 21974 (59.1) | 972 (41.2) | 1.0 | 750 (69.8) | 222 (17.3) | <0.001* |
| Instrumental vaginal | 6013 (15.2) | 5874 (15.8) | 139 (5.9) | 0.5 (0.4 to 0.6) | 103 (9.6) | 36 (2.8) | |
| Elective caesarean | 5201 (13.2) | 4945 (13.3) | 256 (10.8) | 1.1 (1.0 to 1.3) | 0 (0.0) | 256 (19.9) | |
| Emergency caesarean | 5367 (13.6) | 4373 (11.8) | 994 (42.1) | 5.1 (4.6 to 5.6) | 222 (20.7) | 772 (60.0) | |
| GA, median (IQR), weeks | |||||||
| Extremely preterm (<28 weeks) | 209 (0.5) | 39.6 (37–41) | 35 (33–36) | 33.1 (19–36) | 33.3 (23–36) | 0.202 | |
| Very preterm (28 to <32 weeks) | 342 (0.2) | – | 209 (8.9) | – | 122 (11.3) | 87 (6.8) | <0.001* |
| Moderate to late preterm | 1810 (4.3) | – | 342 (14.5) | – | 130 (12.1) | 212 (16.5) | |
| (32 to <37 weeks) | – | 1810 (76.7) | – | 823 (76.6) | 987 (76.7) | ||
| Birth weight (g) median (IQR) | 3411.0 (598.8) | 3471.1 (481.5) | 2057.3 (729.0) | <0.001* | 2270.0 (1697.5–2665.0) | 2020.0 (1485.0–2470.0) | <0.001* |
| Apgar score | |||||||
| ≥7 | 37159 (94.2) | 35468 (95.4) | 1691 (71.1) | 1.0 | 792 (74.3) | 899 (69.9) | |
| <7 | 2290 (5.8) | 1691 (4.6) | 661 (28.9) | 8.5 (7.5 to 9.4) | 274 (25.7) | 387 (30.1) | 0.019* |
| Congenital anomalies | |||||||
| Yes | 298 (0.8) | 250 (0.7) | 48 (2.0) | 2.0 (2.2 to 4.1) | 17 (1.6) | 31 (2.4) | 0.188 |
| No | 39230 (99.2) | 36917 (99.3) | 2313 (98.0) | 1.0 | 1058 (98.4) | 1255 (97.6) | |
Data presented as n (%).
Χ2 test assessed the relationship between categorical variables.
Independent sample t-test compared the means of continuous variables.
*May not add to total number due to missing; the analyses excluded 2834 women with post-term pregnancies.
† Term deliveries were defined as deliveries between 37+0 and 40+6 weeks’ gestation.
‡ Preterm deliveries were defined as deliveries before 36+6 weeks’ gestation.
§ Unadjusted ORs and 95% CIs of PTD, with term deliveries as reference category.
BMI, body mass index; ePTD, elective preterm delivery; GA, gestational age at delivery; PTD, preterm delivery; sPTD, spontaneous preterm delivery.