Factors that affect the chances of conceiving:

A number of factors affect your chances of conception. They include the following:

The table below, (adapted from data in Taylor 2003) identifies some of the significant factors affecting one’s chance of conception.

Increased chance of conception Reduced chance of conception
Woman aged under 30 years Women aged over 35 years
Previous pregnancy No previous pregnancy
Less than three years trying to conceive More than three years trying to conceive
Intercourse occurring during the few days before and/or the day of ovulation Intercourse incorrectly timed, not occurring within the few days before and/or the day of ovulation
Woman's body mass index (BMI) 20-30 Woman's BMI < 20 or > 30
Both partners non-smokers One or both partners smoke
Caffeine intake less than two cups of coffee daily Caffeine intake more than two cups of coffee daily
No use of recreational drugs Regular use of recreational drugs

While some of the factors are beyond one’s control (such as age, time trying, and previous pregnancies), others are more possible to control. Particularly, identifying your fertile window and focusing intercourse within that time can dramatically increase your conception probabilities (Hilgers et al 1992; Gnoth et al 2005).

Since so many factors may come into play, it is not possible to precisely estimate your conception chances each cycle. However, when you are charting your fertility signs and examining your chart for possible clues about your pregnancy chances, the best thing to see is a clear ovulation pattern (best when correlated with multiple fertility signs) and well-timed intercourse within your fertile window.


Baird, D. D. and B. I. Strassman (2000). Women's Fecundability and Factors Affecting It. Women and Health. M. Goldman and M. Hatch. San Diego, Academic Press: 126-137.

Gnoth, C., E. Godehardt, et al. (2005). "Definition and prevalence of subfertility and infertility." Hum Reprod 20(5): 1144-1147.

Hilgers, T. W., K. D. Daly, et al. (1992). "Cumulative pregnancy rates in patients with apparently normal fertility and fertility-focused intercourse." J Reprod Med 37(10): 864-6.

Taylor, A. (2003). "ABC of subfertility: extent of the problem." Bmj 327(7412): 434-6.

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