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How age affects fertility?

How age affects fertility?

You may be thinking of planning a pregnancy or delaying the start of your family and wondering what will happen as your age increases, how it affects your fertility. Today we will discuss the same.

NATURAL FERTILITY

It has been seen in women that the natural fertility peaks between the ages of 20 & 24, decreases relatively little until the age of 30-32 years and then declines progressively.

Age (Years)Overall Fertility Rate
25-294-8% lower
30-3415-19% lower
35-3924-46% lower
40-4595% lower

The same is true for the success rate achieved with various methods to achieve conception like IUI, IVF, etc. As the age of the women increases, the pregnancy rates decline.

MISCARRIAGE

This is due not only to decreasing fertility but also to increased rate of miscarriage. When you are trying to conceive naturally, miscarriage rates are generally low before the age of 30 and rise with age.

Age (Years)Miscarriage Rate
<307-15%
30-348-21%
35-3917-28%
>=4034-52%

Up to 60% of all conceptions miscarry within the first 1 weeks of gestation and 20-40% of all early pregnancy losses go unrecognized. Women over the age of 40 years have a miscarriage rate of nearly 75 %.

OVARIAN AGING AND DECREASE IN NUMBER OF EGGS

The number of eggs peaks at around the 5th month of pregnancy when there are 60-70 lakhs eggs in the ovaries of a growing female baby. This number declines to 10-20 lakhs at birth and to 3-4 lakhs at puberty. Over the next 35-40 years of reproductive life, only about 400 eggs will mature and be released (ovulate). The rest keep on getting lost. By the age of 40 years, the number of follicles will shrink to around 25000 and at menopause when the periods stop less than 1000 eggs remain.

 So male factors generally contribute little to the age-related decline in fertility.

HOW WILL YOU RECOGNIZE YOUR OVARIES HAVE STARTED AGING?

The aging of ovaries is quite advanced when the first clinical signs appear. The cycles remain regular but the cycle length and irregularity decrease and are lowest at the age of 42 years when fertility is nearly at an end.

However, women take notice only when the cycles become irregular which is the start of transition period to menopause. Increasingly the egg release becomes less regular and frequent and the cycle length and irregular cycles increase. After the onset of irregular menses, menopause generally occurs in 5-6 years.

 So your age is the best sign of the aging of your ovaries.

WHAT ARE THE CAUSES OF DEPLETION OF EGGS IN THE OVARIES?

Other than any diseases that destroy the ovaries or require removal of ovaries or part of it, or any important environmental factors, genetics determines the number of eggs at birth and the age at which they are exhausted. Genetics plays an important role as we that-

  • The age of menopause in mothers and daughters and between sisters has a good correlation.
  • The genetic features of early menopause (40-45 years) and premature ovarian failure (POF) are similar.
  • Women who repeatedly have a poor egg formation with hormone injections also tend to have an earlier menopause.

The studies show that the age-related decline in fertility in women and the increase in the risk of miscarriage id due to an increased in the proportion of genetically abnormal eggs in the aging ovary. Lifestyle factors also have a role in this depletion of eggs in the ovaries.

WHAT ARE THE EFFECTS OF OVARIAN AGING ON PREGNANCY TREATMENT?

As age increases, the eggs become less sensitive to hormone injections

So total dose and duration of treatment required for egg formation in IVF increases.

The number and quality of eggs obtained in IVF treatment decreases.

 Due to poor egg quality, the resulting embryos are also of not good quality so either there is no pregnancy or if pregnancy results, the chances of miscarriage are very high.

EFFECT OF AGE ON THE UTERUS

Aging itself does not have much effect on the uterus and its ability to carry a pregnancy. But diseases of the uterus like fibroids, adenomyosis, polyps, etc become more common with increasing age. 

 EFFECT OF AGE ON MALE FERTILITY

With increasing age, there is a decrease in male fertility with a decline in semen volume, sperm motility, and normal sperm. The sperm count may also be affected. So the time to conception increases with the male age. But there is little or no overall decline infertility in men before the age of 45-50 years.