What determines sperm health?

Sperm health depends on various factors, including quantity, movement and structure:

• Quantity. You're most likely to be fertile if your ejaculate — the semen discharged in a single ejaculation — contains at least 15 million sperm per milliliter. Too little sperm in an ejaculation might make it more difficult to get pregnant because there are fewer candidates available to fertilize the egg.
• Movement. To reach and fertilize an egg, sperm must move — wriggling and swimming through a woman's cervix, uterus and fallopian tubes. This is known as motility. You're most likely to be fertile if at least 40% of your sperm are moving.
• Structure (morphology). Normal sperm have oval heads and long tails, which work together to propel them. While not as important a factor as sperm quantity or movement, the more sperm you have with a normal shape and structure, the more likely you are to be fertile.