During the three year study period there were 19
805 teenage pregnancies of which 18
692 (94.4%) could be allocated to a general practice in Trent. Of these, 10
554 (56.5%) resulted in a delivery, 7155 (38.3%) in a termination, and 983 (5.3%) in a miscarriage. In total, 957 (5.1%) pregnancies were to females under 16 years of age. From our NHS dataset the overall median teenage pregnancy rate in Trent for 13 to 16 year olds was 45.0 per 1000 (interquartile range 25.6-74.1); the rate for 13 to 15 year olds was 1.8 per 1000 (0.0-5.5).
Characteristics of general practices
In 1997 there were 826 general practices in Trent, of which 627 (75%) were wholly, predominantly, or mainly urban according to Carstairs' categories.12
The study practices (table ) had similar characteristics to other practices in England and Wales. For example, 350 practices (42.4% of 826) did not have a female doctor, which is comparable to the national figure of 41.7%.
Characteristics of 826 study general practices in Trent. Values are numbers (percentages) unless stated otherwise
Lower incidence rate ratios (lower teenage pregnancy rates) were associated with more nurse time or female or young doctors (table ). A young doctor (under 36 years) was defined as a doctor in the lowest quartile for age calculated from the ages of all the general practitioners in Trent for whom we had data. Higher teenage pregnancy rates were significantly associated with increasing deprivation scores and fundholding status.
Univariate Poisson regression analysis for pregnancies (terminations and deliveries)
On multivariate analysis, practices with at least one female doctor, a young doctor, or more practice nurse time had significantly lower teenage pregnancy rates (table ). Deprivation and fundholding remained significantly associated with higher teenage pregnancy rates.
Multivariate Poisson analysis for pregnancies (terminations and deliveries)
Distance to family planning clinics
The distance (km) from each surgery to the nearest family planning clinic was included in the multivariate analysis, adjusting for each of the variables listed in table . Overall, practices that were far from family planning clinics had lower teenage pregnancy rates (adjusted incidence rate ratio 0.98, 95% confidence interval 0.97 to 0.99; P=0.001). This was mainly due to the effect of rurality since rural practices were far from family planning clinics and had lower rates (0.98, 0.97 to 0.99; P=0.003). In urban practices there was no association between teenage pregnancy rates and distance from family planning clinics (1.01, 0.99 to 1.02; P=0.15).
Analysis including miscarriages
We repeated the analyses including the number of miscarriages in the total number of pregnancies per practice. We found no substantial changes in the direction or significance of any of the variables.
Analysis of excluded practices
Table shows the data available for each practice. It was not possible to calculate teenage pregnancy rates in 116 practices (14%) owing to missing denominators. The number of whole time equivalent practice nurses was similarly unavailable for 255 practices (31%). Practices with and without missing data were similar for all practice characteristics under investigation.