Elizabeth says...

Gemma, 19, Bristol asks...

I've heard that at a certain point during your menstrual cycle it's
impossible to get pregnant. Is this true, and if so, how do you work out
when your 'window' is?

Elizabeth says...

Tread carefully. The Rhythm Method, or Safe Period, as this form of natural
birth control is sometimes known, is the preferred method of contraception
for practising Catholics but before I describe how it works, may I remind
you that Catholics tend to produce rather large families (you do the
maths!). Now that I've got that off my chest, let me give you the facts.
Firstly, you're right, there is a time every month when a woman can't fall
pregnant and this cluster of infertile days tends to fall around the time of
her period - ie. the days just before and just after her bleed. Conversely,
the most fertile time tends to come approximately half way through the cycle - ie. more or less 14 days after a period. But I must stress the words more
or less, as this 'window' of fertility varies from woman to woman and cycle
to cycle so it would be mad to use your period as a gauge for when it's safe
to have unprotected sex. The only reliable way to work out when you're
ovulating (and therefore fertile) is to monitor your vaginal temperature and
the stickiness of your vaginal fluids on a daily basis (visit the Family
Planning clinic at your GP practice for more information), however it takes
commitment to collect this data properly. There's also a device called
Persona - a computerised hand-held monitor with urine test sticks - which
measures the hormonal changes in your body, however motivation and
commitment are essential to use this machine properly, and long-term this
can work out expensive. To sum-up, my advice is: think carefully before
embarking on the Rhythm Method. It's worth considering if you're in a stable
relationship and having a baby is something you'd half welcome, however if
ankle-biters have no place in your short-term plans, please reconsider.