The older that such fish become, the more mercury they may have absorbed. Anything that eats these fish within the food chain also consumes the higher level of mercury that the fish have accumulated. This process explains why predatory fish such as swordfish and sharks or birds like osprey and eagles have higher
The goal, then, when it comes to having a boy is to increase the likelihood that a Y chromosome sperm reaches the egg first. Many medical researchers believe that Y chromosome sperm are faster swimmers, but that X chromosome sperm have more endurance.
Because sperm can fertilize an egg for 72 hours (3 days) after ejaculation, having sex during a girl's period is risky. Having unprotected sex at any time is risky: Along with the chance of getting pregnant, you can also get a sexually transmitted disease (STD), such as chlamydia, genital warts, or HIV.