Contraceptive failure may be a major factor in teenage pregnancy

BMJ 1995; 311 doi: https://doi.org/10.1136/bmj.311.7008.806b (Published 23 September 1995) Cite this as: BMJ 1995;311:806
  1. E S Williams
  1. Director of public health medicine Croydon Health, Croydon, Surrey CR0 6SR

    EDITOR,--In their study of 147 teenagers with unplanned pregnancies V A H Pearson and colleagues found that 80% claimed to have been using contraception at conception.1 The authors argue that teenagers need to lower their threshold for use of emergency contraception when there is a risk of pregnancy.

    It should be a matter of concern that such a high proportion of unplanned pregnancies are due to contraceptive failure (which comprises technical failure and misuse of contraception). To gain an insight into the effectiveness of contraception in preventing teenage pregnancies at a population level I have examined the relation between trends in the use of condoms among teenagers and trends in teenage conception rates during 1975-91. I used data from the national survey of sexual behaviour2 to estimate the proportion of male teenagers who used condoms at first sexual intercourse during the period. The percentage who report having used condoms at first sexual intercourse is available for each year. Pregnancy rates in those aged under 16 and under 19 were obtained from routinely published data.3 I calculated a correlation coefficient for both age groups and found a highly significant positive correlation between teenage conceptions and male use of condoms (under 16: r=0.8553, P=0.001; under 19: r=0.7967, P=0.001). The figure shows a scatter graph with the regression line for the under 16 age group. These findings show a strong positive relation between use of a condom at first sexual intercourse and teenage pregnancy, with pregnancies increasing with increasing use of condoms.


    Conception rate among under 16 year olds by male use of condoms at first sexual intercourse (data are annual figures for 1975-91)

    Sex education and the national camapaign to promote contraception through safer sex campaigns have undoubtedly been successful in increasing the proportion of teenagers who use condoms. Most people have assumed that increasing the use of contraception leads to a reduction in unplanned teenage pregnancies.4 Yet my analysis shows that this has not happened. A plausible explanation is that the main factor in unplanned teenage conceptions is contraceptive failure, not the lack of contraceptive knowledge and availability. The findings of Pearson and colleagues support this view.

    A further question is whether increasing the availability of contraception leads to an increase in sexual activity. If this is the case--and the national survey of sexual behaviour reports a large increase over the past two decades in the proportion of teenagers who are sexually active--then it is not surprising that the rate of teenage conceptions continues to increase. The answer is not more contraception or emergency contraception but a change in attitude towards sexual behaviour.


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