Sociodemographic and obstetric characteristics of preterm deliveries stratified by maternal BMI
| Underweight BMI<18.5 kg/m2 n=56 | Normal weight BMI 18.5–24.9 kg/m2 n=1077 | Overweight BMI 25.0–29.9 kg/m2 n=660 | Mildly obese BMI 30.0–34.9 kg/m2 n=295 | Moderate/severely obese BMI>35.0 kg/m2 n=156 | p Value | |
| GA at delivery | ||||||
| Extremely preterm (<28+0 weeks) | 5 (8.9) | 75 (7.0) | 57 (8.6) | 35 (11.9) | 11 (7.1) | 0.242 |
| Very preterm (28+1–31+6 weeks) | 7 (12.5) | 138 (12.8) | 97 (14.7) | 39 (13.2) | 25 (16.0) | |
| Moderate to late preterm (32+0–36+6 weeks) | 44 (78.6) | 864 (80.2) | 506 (76.7) | 221 (74.9) | 120 (76.9) | |
| Type of PTD | ||||||
| sPTD | 33 (58.9) | 550 (51.1) | 275 (41.7) | 105 (35.6) | 52 (33.3) | <0.001 |
| ePTD | 23 (41.1) | 527 (48.9) | 385 (58.3) | 190 (64.4) | 104 (66.7) | |
| Parity | ||||||
| Nulliparous | 29 (51.8) | 535 (49.7) | 263 (39.8) | 122 (41.4) | 59 (37.8) | <0.001 |
| Multiparous | 27 (48.2) | 542 (50.3) | 397 (60.2) | 173 (58.6) | 97 (62.2) | |
| Type of pregnancy* | ||||||
| Singleton | 51 (91.1) | 885 (82.2) | 534 (80.9) | 252 (85.4) | 135 (86.5) | 0.108 |
| Multiples | 5 (8.9) | 192 (17.8) | 126 (19.1) | 43 (14.6) | 21 (13.5) | |
| Maternal age (year) | ||||||
| <20 | 6 (10.7) | 67 (6.2) | 13 (2.0) | 3 (1.0) | 3 (1.9) | <0.001 |
| 20–24 | 13 (23.2) | 142 (13.2) | 64 (9.7) | 33 (11.2) | 15 (9.6) | |
| 25–29 | 14 (25.0) | 248 (23.0) | 115 (17.4) | 65 (22.0) | 35 (22.4) | |
| 30–34 | 11 (19.6) | 315 (29.2) | 221 (33.5) | 100 (33.9) | 51 (32.7) | |
| 35–39 | 9 (16.1) | 235 (21.8) | 190 (28.8) | 66 (22.4) | 40 (25.6) | |
| ≥40 | 3 (5.4) | 70 (6.5) | 57 (8.6) | 28 (9.5) | 12 (7.7) | |
| Nativity | ||||||
| European Irish | 35 (63.6) | 790 (74.9) | 470 (72.8) | 191 (65.4) | 140 (68.0) | <0.001 |
| European non-Irish | 10 (18.2) | 177 (16.8) | 92 (14.2) | 45 (15.4) | 24 (15.7) | |
| Afro-Caribbean | 2 (3.6) | 26 (2.5) | 39 (6.0) | 38 (13.0) | 20 (13.1) | |
| Asian | 8 (14.5) | 61 (5.8) | 43 (6.7) | 18 (6.2) | 5 (3.3) | |
| Hispanic | 0 (0.0) | 1 (0.1) | 2 (0.3) | 0 (0.0) | 0 (0.0) | |
| Maternal occupation | ||||||
| Professional/managerial | 10 (18.5) | 233 (21.9) | 134 (20.6) | 45 (15.6) | 24 (15.7) | 0.024 |
| Other non-manual/skilled manual | 6 (11.1) | 168 (15.8) | 83 (12.8) | 34 (11.8) | 15 (9.8) | |
| Semiskilled/unskilled manual | 24 (44.4) | 492 (46.2) | 328 (50.5) | 151 (52.4) | 90 (58.8) | |
| Unemployed | 14 (25.9) | 172 (16.2) | 105 (16.2) | 58 (20.1) | 24 (15.7) | |
| Prenatal care | ||||||
| Regular attendance | 45 (93.8) | 822 (94.9) | 501 (95.4) | 207 (96.3) | 119 (96.7) | 0.809 |
| Poor attendance | 3 (6.3) | 44 (5.1) | 24 (4.6) | 8 (3.7) | 4 (3.3) | |
| Mode of delivery | ||||||
| Elective CS | 10 (17.9) | 121 (11.2) | 69 (10.5) | 25 (8.5) | 27 (17.3) | <0.001 |
| Emergency CS | 16 (28.6) | 390 (36.2) | 310 (47.0) | 149 (50.5) | 73 (46.8) | |
| Assisted vaginal delivery | 2 (3.6) | 87 (8.1) | 28 (4.2) | 15 (5.1) | 4 (2.6) | |
| Spontaneous vaginal delivery | 28 (50.0) | 479 (44.5) | 253 (38.3) | 106 (35.9) | 52 (33.3) | |
| Birth weight (singletons) | ||||||
| 2500–4500 g | 13 (23.2) | 318 (29.5) | 199 (30.2) | 79 (26.8) | 54 (34.6) | 0.377 |
| <2500 g | 43 (76.8) | 759 (70.5) | 460 (69.8) | 216 (73.2) | 102 (65.4) | |
| NICU admission | 26 (54.2) | 473 (54.6) | 310 (59.0) | 132 (61.1) | 71 (56.8) | 0.339 |
| Congenital anomalies† | 1 (1.8) | 22 (1.8) | 12 (2.0) | 6 (2.6) | 4 (2.0) | 0.983 |
*Includes twin, triplet and quadruplet pregnancies.
† Congenital anomalies include: chromosomal anomaly, cardiac anomaly, cleft palate and/or lip, neural tube defect, diaphragmatic hernia, cystic hygroma, haemangioma.
BMI, body mass index; CS, caesarean section; ePTD, elective preterm delivery; GA, gestational age; NICU, neonatal intensive care unit; PTD, preterm delivery; sPTD, spontaneous preterm delivery.