Table 1.
Baseline characteristics of the study population
| Total pregnancies, n = 388 142 | NRT prescribed, total n = 7551 (% of pregnancies with NRT prescription) | Pregnancies among smokers,an = 71 685 | NRT prescribed, n = 7551 (% of pregnancies among smokers with NRT prescription) | |
|---|---|---|---|---|
| Age at conception, years | ||||
| 5–19 | 27 365 | 930 (3.4) | 9898 | 930 (9.4) |
| 20–24 | 66 484 | 1962 (3.0) | 19 849 | 1962 (9.9) |
| 25–29 | 105 967 | 2004 (1.9) | 19 188 | 2004 (10.4) |
| 30–34 | 118 031 | 1664 (1.4) | 14 534 | 1664 (11.4) |
| 35–39 | 59 541 | 832 (1.4) | 6952 | 832 (12.0) |
| 40–44 | 10 222 | 152 (1.5) | 1203 | 152 (12.6) |
| 45–49 | 532 | 7 (1.3) | 61 | 7 (11.5) |
|
| ||||
| Townsend score in quintilesb | ||||
| Quintile 1 – most affluent | 83 203 | 722 (0.9) | 7970 | 722 (9.1) |
| Quintile 2 | 71 045 | 925 (1.3) | 9511 | 925 (9.7) |
| Quintile 3 | 76 619 | 1432 (1.9) | 14 291 | 1432 (10.0) |
| Quintile 4 | 73 470 | 2068 (2.8) | 18 097 | 2068 (11.4) |
| Quintile 5 – most deprived | 55 653 | 1875 (3.4) | 16 925 | 1875 (11.1) |
| Missing | 28 152 | 529 (1.9) | 4891 | 529 (10.8) |
|
| ||||
| Pre-conception body mass index, kg/m2 | ||||
| Normal (18.0–24.9) | 118 832 | 2266 (1.9) | 22 888 | 2266 (9.9) |
| Underweight (<18.0) | 8614 | 256 (3.0) | 2353 | 256 (10.9) |
| Overweight (25–29.9) | 58 693 | 1237 (2.1) | 11 464 | 1237 (10.8) |
| Obese (≥30) | 42 281 | 992 (2.3) | 9191 | 992 (10.8) |
| Missing | 159 722 | 2800 (1.8) | 25 789 | 2800 (10.9) |
|
| ||||
| Asthma | 33 724 | 1061 (3.1) | 8188 | 1061 (13.0) |
|
| ||||
| Hypertension | 9992 | 154 (1.5) | 1420 | 154 (10.8) |
|
| ||||
| Diabetes | 10 752 | 224 (2.1) | 1798 | 224 (12.5) |
|
| ||||
| Mental illness | 37 055 | 1547 (4.2) | 11 624 | 1547 (13.3) |
a
Smoker classified as those with a record of current smoking at some point within the 27 months before conception until delivery.
b
Socioeconomic status. NRT = nicotine replacement therapy.