Egg and Sperm
Bay IVF - Advanced Reproductive Care                                Palo Alto  650-322-0500


Optimizing Natural Fertility

Adapted from the American Society for Reproductive Medicine (ASRM).

Fertility is defined as the capacity to produce a child. The likelihood of conception is generally highest in the first few months of unprotected intercourse and declines gradually thereafter.

Approximately 80% of couples will conceive in the first six months of attempting pregnancy. Monthly fecundability (the probability of pregnancy per month) is greatest in the first three months. Relative fertility is decreased by about half at age 40 compared with women in their late 20s and early 30s, the time of peak fertility.

Markers of ovarian reserve also decline with increasing age but are poor predictors of fecundity in non-infertile women.

Although semen parameters in men also decline detectably over 35 years of age, male fertility does not appear to be affected before approximately age 50.

Infertility is a disease defined as the failure to achieve a successful pregnancy after 12 months or more of regular unprotected intercourse. Earlier evaluation and treatment may be justified based on medical history and physical findings and is warranted after six months without conception for women 35 years and older due to the age-related decline in fertility.

For counseling purposes, the ‘‘fertile window’’ is best defined as the 6-day interval ending on the day of ovulation. At least, in theory, the viability of both oocytes and sperm should be maximal during that time.

Peak fecundability was observed when intercourse occurred within 1- 2 days prior to ovulation. Age does not affect the length or timing of the fertile window in relationship to ovulation.

A widely held misperception is that frequent ejaculations decrease male fertility. A study that analyzed almost 10,000 semen specimens observed that in men with normal semen quality, sperm concentrations and motility remain normal, even with daily ejaculation. Abstinence intervals greater than five days may adversely affect sperm counts.

In one study, cycle fecundity was similar with intercourse that occurred daily, every other day, and even every three days in the fertile window, but was lowest when intercourse occurred only once in the fertile window.

Although many women think that remaining supine for an interval after intercourse facilitates sperm transport and prevents leakage of semen from the vagina, the belief has no scientific foundation.

There is no evidence that coital position affects fecundability. Sperm can be found in the cervical canal seconds after ejaculation, regardless of the coital position. Although female orgasm may promote sperm transport, there is no known relationship between orgasm and fertility. There also is no convincing evidence to indicate any relationship between specific coital practices and infant gender.

High levels of caffeine consumption (more than 5 cups of coffee/day or its equivalent) have been associated with decreased fertility. During pregnancy, caffeine consumption over 2-3 cups per day may increase the risk for miscarriage but does not affect the risk for congenital anomalies.

Overall, moderate caffeine consumption (1 to 2 cups of coffee per day or its equivalent) before or during pregnancy has no apparent adverse effects on fertility or pregnancy outcomes. In men, caffeine consumption has no effect on semen parameters.

The American College of Obstetricians and Gynecologists recommends that women who are pregnant or may become pregnant should discontinue cannabis use due to the adverse effects of smoking and concerns for impaired fetal neurodevelopment. The use of other recreational drugs by men and women desiring pregnancy is also discouraged due to the risk for pregnancy and neonatal complications.

A growing body of evidence suggests that exposure to synthetic and naturally occurring environmental chemicals in food, water, air, and consumer products may contribute to reduced fertility in men and women.

The adverse effects of air pollution on fertility is another area of growing concern. Higher exposure to ambient air pollution has been linked to lower fertility rates in Europe, the United States, and China. Previous studies have shown that couples who live closer to major roadways have a higher risk of infertility compared to couples who live further away.

Numerous studies have also linked increased air pollution exposure to impaired semen parameters, including higher sperm DNA fragmentation and aneuploidy, lower sperm morphology and motility, and altered reproductive hormone levels.

Reproductive-aged men and women should be encouraged, to the extent possible, to limit their exposure to endocrine-disrupting chemicals in food, air, water, and personal care products.


  • Time to conception increases with age. For women over age 35 years, consultation with a reproductive specialist should be considered after six months of unsuccessful efforts to conceive.
  • Intercourse, every 1-2 days during the fertile window, can help maximize fecundability.
  • For couples who are unable to have regular, frequent intercourse, fertility awareness methods may help time infrequent intercourse to the fertile window and decrease time to pregnancy.
  • Smoking and recreational drugs should be discouraged in men and women attempting pregnancy.
  • Alcohol and caffeine use should be limited to minimal to moderate use while trying to conceive.
  • A healthy lifestyle and diet should be encouraged in people attempting pregnancy for general health and pregnancy.
  • Women wishing to become pregnant should take a daily folic acid supplement (400mcg).
  • Reproductive-aged men and women should be encouraged, to the extent possible, to limit their exposure to endocrine-disrupting chemicals in food, air, water, and personal care products.


May 2021



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