It is not only the issue of hosing sperm close to the cervix but some other health reasons like lack of mighty strong sperm and  healthy egg that are not fertilizing well. On the other hand if the fluid produced by female is too think and sticky makes the sperm hard to swim upspring by the time they are next to egg may not able penetrate the egg and die next to it.  
Along with hosing sperm close to the cervix, couples need to be healthy mentally and physically. Need to eat folic acid and fish product more. Now days the way the chemical is used in food product is the root cause of weak and low count in sperm as well the egg. Life style has been changed so does with the fertility, lust changing the love making style and hosing sperm close to the cervix is not an ultimate solution.
Have you heard  heard the girl got pregnent from swimming pool, if it was real how that happen?