Merck Manual

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Overview of Infertility


Robert W. Rebar

, MD, Western Michigan University Homer Stryker M.D. School of Medicine

Last full review/revision Jan 2019| Content last modified Jan 2019
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Infertility is usually defined as inability of a couple to conceive after 1 yr of unprotected intercourse.

Infertility is defined as a disease by the WHO.

Frequent, unprotected intercourse results in conception for 50% of couples within 3 mo, for 75% within 6 mo, and for 90% within 1 yr.

Infertility can be caused by the following:

Inability to conceive often leads to feelings of frustration, anger, guilt, resentment, and inadequacy.

Couples wishing to conceive are encouraged to have frequent intercourse when conception is most likely—during the 6 days, and particularly the 3 days, before ovulation. Ovulation is most likely to occur about 14 days before the onset of the next menstrual period.

Measuring morning basal body temperature (BBT) daily can help determine when ovulation is occurring in women with regular menstrual cycles. A decrease suggests impending ovulation; an increase of 0.5° C suggests ovulation has just occurred. However, commercially available luteinizing hormone (LH) prediction test kits, which identify the midcycle LH surge, are probably the best way for women to determine when ovulation occurs and are less disruptive than measuring BBT. BBT can be useful if women cannot afford or do not have access to LH prediction kits. There is no evidence that any test determining when ovulation occurs improves the likelihood of pregnancy in couples having regular intercourse.

Excessive use of caffeine and tobacco, which can impair fertility, is discouraged.

If these measures do not result in pregnancy after ≥ 1 yr, both partners are evaluated. Evaluation begins with history, examination, and counseling. Men are evaluated for sperm disorders, and women are evaluated for ovulatory and tubal dysfunction and pelvic lesions.

Evaluation is done sooner than 1 yr if

  • The woman is > 35.

  • The woman is know to have a decreased ovarian reserve (eg, because she has only one ovary).

  • The woman has infrequent menses.

  • The woman has a known abnormality of the uterus, fallopian tubes, or ovaries.

  • The man is known to be subfertile or is at risk of subfertility.

Evidence that men > 45 are less fertile than younger men, regardless of their female partner's age is increasing.

Support groups for couples (eg, Path2Parenthood, RESOLVE) may help. A clinician should discuss adoption if the likelihood of conceiving is low (usually confirmed after 3 yr of infertility, even in women < 35, or after 2 yr of treatment).

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NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
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