Natural Fertility in Couples Planning Pregnancy

Healthcare providers are frequently consulted by couples concerned about their fertility potential. Some couples seek this information even before attempting pregnancy or meeting criteria for subfertility. These couples are especially motivated to listen to advice concerning the impact of lifestyle factors on fertility, as well as their general health.

Some lifestyle factors appear to affect the duration of time before achieving pregnancy; these effects tend to be small and cumulative. Epidemiological studies suggest that lifestyle modifications can improve fertility potential.

Infertility is the inability to conceive despite frequent coitus. Infertility refers to a state in which the capacity for fertility is diminished, but not necessarily absent. For this reason, the term subfertility is often used instead of infertility. Women under age 35 are evaluated for infertility after 12 months of unsuccessful attempts to conceive; women age 35 and older are evaluated after six months.

Within each cycle, the fertile interval extends from approximately five days prior to ovulation to the day of ovulation. The highest probability of conception occurs when intercourse takes place one to two days prior to ovulation. Semen quality is affected by the length of abstinence. Most data indicate that optimum semen quality, measured in terms of motility, morphology, and total sperm count, occurs when there are two to three days of ejaculatory abstinence; longer intervals are associated with lower pregnancy rates.

The probability of conception is also highly dependent upon maternal, and to a lesser extent paternal, age. In a large well-designed study, the probability of clinical pregnancy following intercourse on the most fertile day of the cycle in women of assumed fertility aged 19 to 26 years, 27 to 34 years, and 35 to 39 years was about 50, 40, and 30 percent, respectively, if the male partner was the same age, but 45, 40, and 15 percent, respectively, if he was five years older.

Cigarette smoking, high BMI, and alcohol and caffeine consumption can have a significant adverse impact on pregnancy and fetal outcomes. The combined impact of these exposures on both fertility and pregnancy outcome emphasizes the importance of lifestyle interventions for the couple planning a pregnancy. Cigarette smoking during pregnancy may increase the risk of spontaneous abortion, intrauterine growth restriction, or preterm delivery. A body mass index greater than 30 kg/m2 in the pregnant woman is associated with an increased risk of congenital malformations, preeclampsia, gestational diabetes, fetal macrosomia, and cesarean delivery. Underweight women are at increased risk of low birth weight newborns. Alcohol consumption during pregnancy can cause fetal alcohol syndrome. High caffeine intake appears to increase the risk of spontaneous abortion.

Lifestyle factors can affect the duration of time before achieving pregnancy and modifying these factors may enhance fertility. The recommendations below are based upon data from observational studies; no randomized trials have been performed.

We suggest sexual intercourse two to three times per week to ensure that intercourse falls within the fertile period (up to two days before ovulation) and semen quality is optimal. Couples should be informed that delayed childbearing can decrease the probability of successful conception, and they should take this into account in family and career planning.

We recommend smoking cessation for couples who smoke based on the overall health benefits of smoking cessation. Use of tobacco by the female partner, and possibly the male partner, appears to be associated with subfertility. For couples planning pregnancy, observational studies suggest fertility is enhanced when use of tobacco products is terminated.

A body mass index greater than 27 kg/m2 or less than 17 kg/m2 is associated with an increased risk of anovulatory infertility. The former is often related to polycystic ovary syndrome and the latter is often related to amenorrhea caused by excessive exercise or poor caloric intake (eg, eating disorders). We suggest couples try to achieve a body mass index of 18.5 to 25 kg/m2. Women in this weight range are less likely to have ovulatory dysfunction than women at either extreme of body mass index. This range is associated with little or no increased health risks and, for this reason, is desirable for both women and men.