Table 1.
Characteristics of low-risk women aged 16 and over by maternal age category
| 16–19 years |
20–24 years |
25–29 years |
30–34 years |
35–39 years |
≥40 years |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| n=3354 |
n=11 395 |
n=18 091 |
n=18 453 |
n=10 397 |
n=1681 |
|||||||
| n | Weighted %* | n | Weighted %* | n | Weighted %* | n | Weighted %* | n | Weighted %* | n | Weighted %* | |
| Ethnic group | ||||||||||||
| White | 3078 | 90.1 | 9685 | 81.2 | 15 146 | 77.5 | 16 052 | 80.7 | 9339 | 84.3 | 1527 | 86.6 |
| Non-white | 275 | 9.9 | 1697 | 18.8 | 2920 | 22.5 | 2375 | 19.3 | 1044 | 15.8 | 153 | 13.4 |
| Missing | 1 | 13 | 25 | 26 | 14 | 1 | ||||||
| Understanding of English | ||||||||||||
| Fluent | 3254 | 96.7 | 10 394 | 89.6 | 16 757 | 90.0 | 17 605 | 92.9 | 10 155 | 96.3 | 1638 | 96.7 |
| Not fluent | 94 | 3.3 | 948 | 10.4 | 1251 | 10.0 | 776 | 7.1 | 214 | 3.7 | 36 | 3.4 |
| Missing | 6 | 53 | 83 | 72 | 28 | 7 | ||||||
| Marital/partner status | ||||||||||||
| Married/living with partner | 1836 | 51.9 | 9550 | 81.8 | 16 868 | 92.1 | 17 782 | 96.1 | 10 004 | 95.4 | 1591 | 94.4 |
| Single/unsupported by partner | 1440 | 48.1 | 1677 | 18.2 | 1010 | 7.9 | 493 | 3.9 | 293 | 4.7 | 68 | 5.7 |
| Missing | 78 | 168 | 213 | 178 | 100 | 22 | ||||||
| BMI in pregnancy (kg/m2) | ||||||||||||
| <18.5 | 184 | 6.2 | 426 | 4.2 | 413 | 2.6 | 337 | 2.1 | 156 | 1.5 | 18 | 0.2 |
| 18.5–24.9 | 1753 | 50.3 | 5316 | 45.6 | 8560 | 45.9 | 9059 | 46.7 | 4864 | 44.5 | 802 | 46.4 |
| 25–29.9 | 598 | 17.9 | 2558 | 21.7 | 4341 | 24.6 | 4206 | 23.2 | 2572 | 26.9 | 415 | 27.6 |
| 30–35 | 233 | 7.6 | 1096 | 10.0 | 1627 | 9.3 | 1399 | 8.8 | 769 | 8.9 | 109 | 8.1 |
| Not recorded | 581 | 18.1 | 1969 | 18.4 | 3091 | 17.6 | 3389 | 19.2 | 2000 | 18.3 | 329 | 17.7 |
| Missing | 5 | 30 | 59 | 63 | 36 | 8 | ||||||
| IMD quintile | ||||||||||||
| 1st (least deprived) | 245 | 6.8 | 1102 | 8.5 | 2875 | 13.8 | 4255 | 20.5 | 2783 | 24.6 | 434 | 26.0 |
| 2nd | 405 | 12.3 | 1521 | 13.3 | 3259 | 17.5 | 4114 | 21.7 | 2434 | 22.3 | 396 | 22.0 |
| 3rd | 637 | 18.2 | 2115 | 18.0 | 3657 | 18.6 | 3759 | 19.7 | 2135 | 20.0 | 357 | 21.6 |
| 4th | 827 | 25.3 | 2784 | 23.9 | 3957 | 22.7 | 3479 | 19.8 | 1765 | 17.9 | 291 | 16.9 |
| 5th (most deprived) | 1221 | 37.5 | 3821 | 36.2 | 4262 | 27.5 | 2759 | 18.4 | 1215 | 15.2 | 197 | 13.7 |
| Missing | 19 | 52 | 81 | 87 | 65 | 6 | ||||||
| Previous pregnancies ≥24 weeks | ||||||||||||
| 0 | 2835 | 86.8 | 6341 | 62.0 | 8438 | 53.6 | 7307 | 46.7 | 2989 | 36.9 | 346 | 28.0 |
| 1 | 474 | 12.1 | 3772 | 29.4 | 5892 | 29.9 | 6963 | 33.9 | 3929 | 35.5 | 540 | 32.3 |
| 2 | 38 | 0.8 | 1006 | 6.8 | 2549 | 10.9 | 2779 | 12.2 | 2260 | 17.4 | 414 | 20.2 |
| 3–5 | 7 | 0.3 | 276 | 1.9 | 1212 | 5.6 | 1404 | 7.2 | 1219 | 10.2 | 381 | 19.5 |
| Missing | ||||||||||||
| Gestation at delivery (completed weeks) | ||||||||||||
| 37 | 119 | 4.1 | 351 | 3.5 | 530 | 3.6 | 534 | 3.5 | 275 | 3.1 | 52 | 3.2 |
| 38 | 305 | 11.0 | 1136 | 10.1 | 1743 | 9.9 | 1739 | 9.9 | 971 | 10.2 | 146 | 9.9 |
| 39 | 783 | 22.5 | 2788 | 24.4 | 4409 | 24.2 | 4439 | 23.5 | 2516 | 23.2 | 410 | 27.2 |
| 40 | 1292 | 36.7 | 4361 | 36.7 | 6970 | 36.2 | 7090 | 37.5 | 3933 | 35.9 | 639 | 35.0 |
| 41–42+0 days | 855 | 25.7 | 2759 | 25.3 | 4439 | 26.1 | 4651 | 25.6 | 2702 | 27.7 | 434 | 24.7 |
| Planned place of birth | ||||||||||||
| OU | 1445 | 87.5 | 4150 | 84.9 | 5601 | 82.6 | 4946 | 80.7 | 2571 | 80.2 | 497 | 83.2 |
| AMU | 1038 | 8.5 | 3445 | 9.6 | 4958 | 10.1 | 4540 | 10.3 | 2212 | 9.6 | 294 | 7.9 |
| FMU | 661 | 3.2 | 2115 | 3.5 | 3242 | 3.8 | 3216 | 3.9 | 1674 | 3.8 | 249 | 3.0 |
| Home | 210 | 0.8 | 1685 | 2.0 | 4290 | 3.5 | 5751 | 5.1 | 3940 | 6.4 | 641 | 5.8 |
| Birth weight (g) | ||||||||||||
| <2500 | 53 | 1.9 | 146 | 1.8 | 166 | 1.4 | 159 | 1.1 | 75 | 1.0 | 17 | 1.3 |
| 2500–2999 | 561 | 18.4 | 1728 | 16.4 | 2281 | 14.5 | 1924 | 12.7 | 1100 | 12.5 | 168 | 12.8 |
| 3000–3499 | 1502 | 44.6 | 4678 | 41.1 | 7171 | 39.3 | 6960 | 38.2 | 3644 | 36.5 | 596 | 37.1 |
| 3500–3999 | 977 | 28.4 | 3664 | 30.9 | 6256 | 33.4 | 6767 | 35.0 | 3888 | 35.3 | 617 | 36.9 |
| 4000–4499 | 233 | 6.0 | 1023 | 8.7 | 1926 | 10.0 | 2294 | 11.4 | 1432 | 12.5 | 239 | 9.9 |
| ≥4500 | 21 | 0.7 | 135 | 1.2 | 262 | 1.5 | 303 | 1.6 | 237 | 2.3 | 40 | 2.0 |
| Missing | 7 | 21 | 29 | 46 | 21 | 4 | ||||||
| Complicating conditions identified at the start of care in labour | ||||||||||||
| Prolonged rupture of membranes >18 h | 145 | 7.1 | 411 | 6.1 | 678 | 6.5 | 706 | 7.1 | 415 | 7.0 | 78 | 8.9 |
| Meconium stained liquor | 126 | 5.8 | 322 | 4.8 | 469 | 5.0 | 541 | 6.1 | 295 | 5.9 | 60 | 7.4 |
| Proteinuria 1+ or more | 79 | 2.3 | 203 | 1.7 | 261 | 1.9 | 226 | 1.6 | 109 | 1.7 | 20 | 1.6 |
| Hypertension | 55 | 2.6 | 160 | 2.2 | 232 | 2.4 | 207 | 2.0 | 102 | 2.1 | 17 | 2.0 |
| Abnormal vaginal bleeding | 16 | 0.7 | 57 | 0.9 | 79 | 0.9 | 119 | 1.5 | 77 | 2.1 | 16 | 2.1 |
| Non-cephalic presentation | 5 | 0.2 | 31 | 0.5 | 44 | 0.4 | 64 | 0.5 | 46 | 0.7 | 3 | 0.3 |
| Abnormal fetal heart rate | 41 | 1.5 | 106 | 1.7 | 162 | 1.8 | 143 | 1.7 | 82 | 1.7 | 27 | 3.0 |
| Other complications | 14 | 0.6 | 24 | 0.3 | 23 | 0.2 | 27 | 0.1 | 11 | 0.2 | 2 | 0.2 |
| Any complicating condition | 431 | 18.5 | 1175 | 16.1 | 1744 | 16.6 | 1829 | 18.0 | 1001 | 18.1 | 199 | 22.5 |
*Percentages are weighted to take account of differences in the probability of a woman being selected for inclusion in the study arising from differences in each unit/trust's period of participation and the stratum-specific probabilities of selection of OUs.
AMU, alongside midwifery unit; BMI, body mass index; FMU, freestanding midwifery unit; IMD, index of multiple deprivation; OU, obstetric unit.