Sexual practices also influence fertility. The missionary position results in more babies. That is because this position draws the man's penis further along the cervix, giving sperm a shorter route to fertilizing the egg. Foreplay, on the other hand, reduces chances of conception. During foreplay, the front of the uterus rises. This gives the sperm a longer route to reaching the egg and a greater chance of failing along the route. Men's fertility is greatly influenced by testicular temperature. The warmer the testicles, the lower the fertility. Tight undergarments, such as briefs and Speedos, hold the testicles against the abdomen. This increases heat, and reduces the viability of sperm. Boxer shorts allow the testicles to rest away from the abdomen and allow greater production of viable sperm.
There are no herbs or supplements that absolutely guarantee fertility. Certain herbs and supplements, however, often help. A supplement that is beneficial to both men and women is folic acid. This B vitamin is essential to the normal growth of the "neural tube," the "plumbing" of the central nervous system, in the developing embryo. When the mother is folic acid deficient, there can be a birth defect known as spina bifida. Folic acid deficiencies are also a wholly preventable cause of cleft palate. In men, folic acid supplementation sometimes increases sperm count. Neither men nor women need to take megadoses. Taking just a single B vitamin pill providing only the recommended daily intake (RDI) is usually enough.
Two other common natural supplements also assist fertility, but they are not equally useful for both men and women. The herb vitex can help restore a woman's period and ovulation, making conception possible. In men, however, vitex interferes with and sometimes completely stops sperm production. Zinc supplements are useful in increasing sperm count, but they do not have any special role in women's fertility. Usually just 30 mg a day is enough to correct any zinc deficiency interfering with sperm production.