Women who take the oral contraceptive pill for a lengthy period could find it quicker to get pregnant once they stop than those who used it for shorter periods, according to a study published today in the journal Human Reproduction.
There has been concern over the last twenty years that taking the pill may reduce fertility. Other studies have reported temporary delays for women who have tried to get pregnant after taking oral contraceptives when compared to those using other methods of contraception.
But researchers at Brunel and Bristol Universities investigating more than eight thousand planned pregnancies amongst women in the ALSPAC study, which is based at Bristol University, found that
if they had taken the pill for a long period of time, that is more than five years, there was a greater likelihood of them becoming pregnant within six months.
The information came from 8,497 women in the study, which is known popularly as Children of the 90s. The study has monitored the health, well being and development of over 14,000 families since the early 90s.
The pregnant women and their partners completed questionnaires during pregnancy on a variety of topics including their ages, use of the contraceptive pill, whether they smoked or drank alcohol, their educational achievement, height, weight and the time it had taken to conceive if their pregnancy was planned.
The results showed that 74% conceived within 6 months, 14% between 6 and 12 months and 12% became pregnant after a year.
Those that had taken the pill previously for a prolonged period were statistically less likely to have a delay in becoming pregnant.
75.4% conceived within 6 months if they had been on the pill for more than 5 years compared to 70.5% who had never used it. Of those who conceived within 12 months of stopping the pill, 89.5% had been on the pill for more than five years compared to 85.4% who had never used it.
This was the same for women who had previously had a baby and for those becoming pregnant for the first time. The other social and biological factors that are related to time to conception could not explain these findings.
Dr. Alexandra Farrow, of the Department of Health and Social Care at Brunel, and the lead author of the findings, says that the increasing benefit of greater duration of usage of the pill and its effect on time to conception shown in this study is consistent with a number of possible protective mechanisms the pill may provide.
She goes on to point out that a quarter of women of childbearing age in the UK use the pill as a method of contraception. And although women with prolonged use of the pill might be reassured that they will not be disadvantaged in their attempts to conceive once they stop taking the pill, Dr. Farrow says that these findings must be used with caution until further research confirms our findings.
Notes
Farrow A, Hull M, Northstone K, Taylor H, Ford C, Golding J and the ALSPAC Study Team “Prolonged use of oral contraception before a planned pregnancy is associated with a decreased risk of delayed conception”. Human Reproduction 2002 doi: 10.1093/humrep/17.10.2754
Please acknowledge Children of the 90s in any reporting.
ALSPAC The Avon Longitudinal Study of Parents and Children (also known as Children of the 90s) is a unique ongoing research project based in the University of Bristol. It enrolled 14,000 mothers during pregnancy in 1991-2 and has followed most of the children and parents in minute detail ever since.