Ladies, if you've always thought that your uterus just lies back, chillin and waiting for the right squiggly guy (aka sperm) to fertilise an egg, it turns out that you're wrong.
According to new research from Tel Aviv University, women can, to a certain extent, reject or accept sperm thanks to powerful uterine contractions and the motion of the uterus is argued to be at the core of reproductive success (i.e. whether or not you actually get pregnant). One anthropologist from Cornell has explained it thus:
"...The uterus actually plays a role in make sure sperm are in the right place at the right time. Apparently, uterine contractions squirt fluid, and sperm, upwards.
After conception, the uterus waits below, for about seven days, as the newly fertilized egg takes its own sweet time to float into the womb, and then the uterus goes into action again.
When the egg finally arrives, the uterus begins to contract again, performing a welcoming dance that sucks the new embryo into the soft lining of the uterine wall, and voila, we have a baby on the way."
In theory, evolution dictates then that women are able to choose (unconsciously) the best sperm and create the best genes for the future child. Yet, women often have sex even when they know that their partner is less than perfect, so.....
There goes that theory.
Source: Secret Birth Control Method