Conception is one of the most remarkable events that take place in our human body. A basic understanding and knowledge about normal fertility is beneficial to enable us take the right decisions about one’s reproductive life. This article gives a brief overview about the normal fertility process, time taken to pregnancy and guidance about when to seek help for conception.
The female reproductive system consists of the uterus, two fallopian tubes and two ovaries; all of which are situated in the lower abdomen (pelvis). The functioning of these organs is regulated by hormones secreted by the brain and the pituitary gland. Natural conception involves release of an egg from one of the ovaries (a process called ‘ovulation’) which must be picked up by the fallopian tube. Sexual intercourse around the time of ovulation enables the sperms to travel from the vagina up into the fallopian tube where the egg lies in waiting. The essence of conception is ‘fertilisation’ or the union of the egg and the sperm. The fertilised egg (embryo) travels down the fallopian tube into the uterus where it implants in the lining and continues to grow.
The ‘fertile window’ is the time in a cycle when pregnancy can occur and is usually the six-day interval ending on the day of ovulation. Cycle lengths of approximately 24 to 34 days (from the beginning of one period to the beginning of the next period) are usually ovulatory. If cycles are every 2-3 months or not at all, either ovulation is not happening or is happening infrequently. Generally, ovulation occurs 14 days prior to the next menses (period), so a woman with a 28-day cycle will ovulate around cycle day 14 (that is 14 days after the start of her last menstrual period). That means that intercourse is most likely to result in pregnancy if it occurs within the six-day interval ending the day of ovulation. This fertile window would vary in women having longer or shorter cycles.
Because the fertile window is defined by the date of ovulation, it is important to know when the woman is ovulating. There are several ways to detect ovulation, including observation of changes in cervical mucus, urine test kits to measure LH levels, the basal body temperature (BBT) charting, transvaginal ultrasound, endometrial biopsy, and blood tests to measure hormone levels. These changes can be monitored to successfully identify the fertile window in many women. Cervical mucus and vaginal secretions start to increase 5-6 days prior to ovulation and peak 2-3 days prior to ovulation. Urinary ovulation predictor kits can also be used to detect the rise in luteinizing hormone (LH) that happens just before ovulation. Measuring basal body temperature everyday can be used to predict ovulation, albeit retrospectively.
Pregnancy rates are best when the frequency of intercourse is every 2-3 days during the fertile window. This 2-3 day abstinence (not having intercourse) between ejaculations produces the best quality of semen. Surprisingly, long and shorter (daily) periods of abstinence can decrease the quality of semen, and infrequent intercourse may decrease the chance of intercourse occurring around the time of ovulation. The highest pregnancy rates are seen when a couple has intercourse every 2-3 days during the fertile window.
Sperm ejaculated or released into the vagina reach the fallopian tubes within minutes regardless of position during intercourse. There is no evidence that sexual position, orgasm or prolonged rest after intercourse increases the chance of conception. Many lubricants reduce the quality of the sperms and impair the chances of conception and should be avoided. For fertility safe lubricants, an opinion of a fertility specialist should be sought.
There is scientific evidence to indicate that fertility is decreased in women who are very thin or obese, smokers, heavy alcohol (> 2 drinks per day) or heavy caffeine consumption, and the use of recreational drugs. Therefore, women considering conception should make sure she is healthy enough for pregnancy by taking prenatal vitamins (folic acid), not being overweight, adopting a healthy lifestyle and quitting smoking, caffeine, recreational drugs and alcohol. One must seek appropriate medical advice in case of any coexisting medical or genetic condition in the couple or the family before attempting conception.
A woman’s optimal fertile period is in her 20s. Fertility gradually declines in the 30s, particularly after age 35. A healthy woman in her 20s has a 20% chance of getting pregnant each month that she tries. This ability to conceive diminishes as the woman grows older and as the duration of attempting pregnancy increases. A 40 year old woman has a <5% chance of conception per month. The chances of conception for a woman with regular cycles thus depends both on her age and on the number of months she is trying for conception.
Infertility is typically defined as the inability to achieve pregnancy after one year of regular unprotected intercourse. A couple must seek medical help if they have been unsuccessfully trying to conceive for a year or more. However, if the female partner is 35 years or older, infertility evaluation should begin after about six months of unprotected intercourse rather than a year, so as not to delay potentially needed treatment. Certain situations warrant earlier intervention for example those with irregular menstrual cycles (suggesting that she is not ovulating or releasing an egg), or if either of the couple has a known fertility problem.