In the most normal natural circumstances fertility of women is low. Fecundability is defined as the probability of conceiving within a single menstrual cycle and in healthy couples it is around 25%. This means that if a healthy young couple practices sex at the exact time of ovulation chances of woman conceiving are only 25%. Fecundability of women over 40 years of age is only 4-5%.
Even when a woman gets pregnant 50-60% of those pregnancies end very early. We call this a biochemical pregnancy loss or a pregnancy in which the blood pregnancy hormone levels are increased, but the pregnancy stops developing and beta HCG starts decreasing. Today, it is well known that a large number of early pregnancies are lost, so fecundability should not be mistaken for fecundity, which is defined as the probability to give birth to a living baby of a single menstrual cycle. Fecundity in humans is around 10% which makes us the species with the lowest reproductive rate.
If the pregnancy continues to develop normally, chances of early spontaneous miscarriage (before week 12 of the pregnancy) are between 10 and 15%. Once you go over week 12, miscarriages are rare and the baby is usually born within the set date.
Statistics around the world show us that women are deciding to get pregnant later in life and the greatest increase in achieved pregnancies is seen in women in the 35-39 age-group. However, a gradual decline in fertility in women past the age of 30, and especially in women past the age of 40, is present. Considering all of this, most couples become frustrated when they do not conceive immediately; in the very first or the few first attempts. This means very little to an average couple because most of them get pregnant after a very brief period of trying. Nevertheless, since around 20% of women past the age of 35 are infertile, plans need to be made about what to do if you do not get pregnant after you have tried for some time.
A woman’s ovarian egg reserve rapidly decreases as she approaches menopause. Younger women usually produce a single ripe egg in one cycle, whereas women older than 37 occasionally produce two. This is the reason why “older” women often get pregnant with twins, when compared to younger women.
In addition, biochemical pregnancy loss causes great frustration in women. Before very sensitive pregnancy tests that we have today were introduced to the market, we were unaware of these losses and they were considered as late periods. However, the above mentioned numbers clearly show a need for a bit more patience and longer periods of trying because infertility is defined as inability to conceive after one year of unprotected sex. But, there are exceptions to this rule. Couples in which the female is over the age of 35 need to react sooner and see their doctor after 6 months. This also relates to couples who, for some valid reason, doubt they can conceive.