Table 1. Mean of characteristics and distribution of interventions for nulliparous women delivering vaginally grouped by infant’s birthweight according to smoking status group between 1997 and 2007 in Finland (n = 217,778) (Chi-Square, Kruskal-Wallis tests).
| Characteristic/intervention | <3,000 g | 3,000–3,499 g | 3,500–3,999 g | 4,000–4,499 g | 4,500–4,999 g | ≥5,000 g | Pooled |
| % or mean | % or mean | % or mean | % or mean | % or mean | % or mean | % or mean | |
| OASIS, n (%) | |||||||
| Smoking | 10 (0.2)** | 61 (0.5)** | 80 (0.9)** | 39 (1.7) | 0** | 0 | 190 (0.7)*** |
| Given up smoking | 5 (0.5) | 21 (0.8) | 34 (1.2) | 12 (1.2) | 0 | 0 | 72 (0.9) |
| Non-smoking | 119 (0.5) | 553 (0.9) | 839 (1.3) | 421 (2.0) | 73 (2.8) | 4 (3.2) | 2009 (1.1) |
| Mean maternal age | |||||||
| Smoking | 24.8*** | 24.4*** | 24.3*** | 24.2*** | 27.5*** | 23.9* | 24.4*** |
| Given up smoking | 25.4 | 25.0 | 24.9 | 24. 8 | 24.7 | 23.8 | 25.0 |
| Non-smoking | 28.0 | 27.6 | 27.5 | 27.4 | 23.7 | 27.0 | 27.6 |
| Mean maternal weight (kg) | |||||||
| Smoking | 61.5** | 63.8 | 67.4*** | 69.0 | 71.4 | 81.7 | 64.8* |
| Given up smoking | 61.6 | 63.1 | 67.1 | 69.2 | 73.3 | 87.8 | 65.3 |
| Non-smoking | 62.0 | 63.3 | 65.9 | 68.8 | 72.3 | 75.1 | 64.8 |
| Mean birthweight (g) | |||||||
| Smoking | 2653.0*** | 3258.0*** | 3707.4*** | 4172.4 | 4629.2 | 5098.1 | 3345.5*** |
| Given up smoking | 2656.6 | 3270.8 | 3724.0 | 4181.7 | 4636.2 | 5157.3 | 3490.9 |
| Non-smoking | 2669.1 | 3271.7 | 3719.1 | 4175.6 | 4646.4 | 5151.9 | 3475.5 |
| Mean birth height (cm) | |||||||
| Smoking | 46.8*** | 49.4*** | 50.9*** | 52.3*** | 53.6** | 53.8 | 49.5*** |
| Given up smoking | 46.9 | 49.5 | 51.0 | 52.4 | 53.6 | 54.5 | 50.1 |
| Non-smoking | 47.1 | 49.6 | 51.1 | 52.5 | 53.8 | 55.1 | 50.2 |
| Mean head circumference (cm) | |||||||
| Smoking | 33.0 | 34.2*** | 35.2** | 36.0 | 36.7 | 38.0* | 34.4*** |
| Given up smoking | 32.9 | 34.3 | 35.3 | 36.0 | 36.9 | 39.0 | 34.7 |
| Non-smoking | 33.0 | 34.4 | 35.3 | 36.1 | 36.9 | 37.1 | 34.7 |
| Vacuum | |||||||
| Smoking | 9.5** | 11.7*** | 14.8*** | 18.7 | 20.5 | 0 | 12.8*** |
| Given up smoking | 9.5 | 13.0 | 15.9 | 21.3 | 28.5 | 23.0 | 14.9 |
| Non-smoking | 11.0 | 13.8 | 16.9 | 20.6 | 23.7 | 31.2 | 12.8 |
| Mean length of active 2nd stage (min.) | |||||||
| Smoking | 26.9*** | 34.3*** | 39.8*** | 42.7*** | 54.7* | 32.3 | 35.1*** |
| Given up smoking | 27.6 | 32.6 | 42.4 | 45.6 | 47.5 | 40.0 | 37.4 |
| Non-smoking | 32.8 | 41.0 | 48.1 | 51.0 | 65.3 | 55.0 | 44.3 |
*
p value <0.05,
**
p<0.01,
***
p<0.001.
Information on maternal height and weight, head circumference and length of the active second stage of birth have been recorded in the MBR since 2004 (n = 80,504).