Patient :When a man ejaculates, he releases 98% of the semen, and 2% stays in correct?... a normal ejaculation can contain up to about 500 mil sperm cells, if 2 percent of that stays in the urethra then only 10 mil sperm cells total could be pushed out by pre-ejaculate if he gets another erection after his previous ejaculation, and that's if sex happens immediately again (without urination between sessions). A man that has less than 15 Million sperm cells PER ML (2-5 ml released during ejaculation) is considered to be a cause of infertility. So how can a woman become pregnant even if the man did have 10 million sperm cells left inside of the urethra if that would be considered infertile, and that's if there was even that many left over. Also, after a man ejaculates and becomes soft again, some semen that is left in the urethra can leak out if he hasn't urinated, would that be considered the remaining semen that was left from the ejaculation? Or would there still be a lot left inside? Studies also show that pre-ejaculate does not normally contain sperm cells unless picked up from a previous ejaculation.
A normal sperm count is roughly anything above 20 million/ml. Anything less than that is called a low sperm count (oligospermia) and may be a cause of infertility but does not mean that a man with a low count cannot impregnate his partner.
For pregnancy to take place, as long as active sperm reaches the egg, there is always a possibility that fertilization takes place. Having said that pregnancy is possible with low counts, such cases are extremely rare.
With respect to pre-ejaculate and sperms remaining in the urethra, although it is theoretically possible that the pre-ejaculate contains some sperms, it is extremely rare for a women to conceive only entirely because of these sperms in the pre-ejaculate. This is because the urethra has an acidic pH and generally if there is some deposit of semen in the vagina, the sperms would lose their capacity to fertilize eggs. Such situations are extremely rare and I don't think you should worry about the same.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.