Ask any third-year medical student how hormonal contraception prevents pregnancy, and they’ll probably tell you it prevents ovulation. What they won’t tell you is that this effect is variable and dose-dependent, and if we depended on it alone, hormonal contraception would be much less effective.
That’s because of the very important, and in my opinion, much under-appreciated effect of hormonal contraception on cervical mucus.
A Cervical Mucus Primer
Fertile cervical mucus – which forms under the influence of rising estrogen levels in the first half of the menstrual cycle and is maximal around ovulation –- is thin, watery, clear and easy for sperm to traverse.
Non-fertile mucus — which forms after ovulation and also in pregnancy under the influence of progesterone –- is the exact opposite: Thick,tacky, non-distensible and impossible for sperm to penetrate. (It’s not called the mucus plug for nothing.) Read more »
*This blog post was originally published at tbtam*