Although increased age is not an absolute barrier to pregnancy, the proven fact remains that female fertility gradually decreases with age, lowering the odds that a woman will get pregnant well before the menopause "closes the door" once and for all (unless, of course, you have had your eggs frozen). While the situation with men is a bit different, it's not nearly as different as many people would like to believe. Women are born with all the eggs that they will ever have in their lives while, men, on the other hand, make fresh sperm continuously throughout their lives — but that fact alone says little about its quality.
Reproduction – facts
Reproduction is, in biology, considered to be the most important function in the life of an organism, and all other processes, including senescence and death, are shaped to serve it. It's what perpetuates the existence of a species. There are quite a few different models of reproduction. The most common are semelparous and iteroparous. Semelparous organisms reproduce by a single reproductive act. Annual and biennial plants are semelparous, as are many insects and a few vertebrates, notably salmon and eels. Iteroparous organisms, on the other hand, reproduce recurrently over a reproductive span that usually covers a major part of the total life span.
In addition, some species have the strategy of producing many offspring with the hope that at least a few will survive, while others put all their resources into just a few, or just one — such as elephants and primates, including humans.
Human fertility depends on various factors such as:
- nutrition,
- sexual behavior,
- culture,
- instinct,
- endocrinology,
- timing,
- economics,
- lifestyle,
- emotions
Male and female reproductive system
Most people are not aware that women are born with a fixed number of eggs - about 400,000. Women’s eggs form in their ovaries during the fourteenth week of fetal growth and they will remain there until puberty. However, this number decreases even during early childhood, bringing the number closer to 300,000 by the time a woman reaches puberty. Over the next 35 to 40 years of reproductive life, only 400 to 500 eggs will ovulate and at menopause only a few hundred will remain.
At puberty, the eggs will eventually start to mature — one by one. At ovulation, the egg bursts from the ovary sometimes causing a small, sharp pain. If the egg is not fertilized by the male sperm, the egg will break down within 24 hours into its components and be reabsorbed by the body. Men on the other hand continually produce sperm throughout their lives, millions of cells.
Fertility and age
Although there is still some disagreement over this issue, most fertility experts agree that fertility decreases with age. There is a lot of evidence that points to this trend. Most people believe that nothing can interfere with man’s ability to produce sperm because they can't “run-out” of it! Although men are not born with a fixed number of sperm cells and can usually make more on demand, age and health can affect a man's ability to reproduce. The fact is that there is a decline in testosterone levels as well as sperm motility as a man ages. Sexual activity of most men also decreases with age. The major factors in male reproductive health include the quality of the ejaculate and the frequency of intercourse.
Why does fertility decrease?
The fact is that for a long time now it was not known why fertility decreases with age.
Research has focused on two areas: aging of the uterus versus aging of the eggs. The modern technology of egg donation has enabled experts to look at these factors separately. If fertility decreases because an older woman's uterus is less capable of carrying a pregnancy, then using younger eggs shouldn't produce very many pregnancies in older women. However, several researches have proven exactly the opposite.
Women in their forties, fifties, and even sixties can all achieve very high pregnancy rates with egg donation. This is the proof that fertility decreases with age due to aging of eggs and chromosomes, not aging of the uterus, like some though it was.
Monthly fertility cycles
A less known fact is that both women and men have hormonal cycles which determine when a woman can achieve pregnancy and when a man is most fertile.
Women
The female cycle is approximately twenty-eight days long. Women ovulate approximately on the fourteenth day of their cycle and that is obviously the most fertile time for females.
Men
Men can ejaculate and produce sperm at any time of the month, but their libido dips occasionally, which scientists guess is in relation to their internal cycle.
Increased risk of miscarriage with age
Several researches have been conducted on this subject and they have proven that, in addition to lowering the chance of becoming pregnant, as women age they also have a higher chance of miscarriage. What are the reasons for this? It is proven that the longer an egg sits in the ovary, the more likely it is to develop abnormalities in its chromosomes. This is because mutations are happening inside the ovarian cell all the time. Chromosomes are replacing or loosing some parts and this could become a problem if the process is being active for too many years. If an egg with abnormal chromosomes is fertilized, the chances that the resulting pregnancy will end in miscarriage are greater. Statistic data is saying that a young woman has only a 12-15% chance of having a miscarriage each time she becomes pregnant, while a woman in her 40s hasa 50% risk of miscarriage.
Fertility tests
FSH test
There are several tests which are made to determine the fertility levels. The most important test which is made to determine a woman's fertility level is a blood test called FSH- Follicle Stimulating Hormone. This hormone is made in a gland near the brain, called the pituitary. It is the most important hormone responsible for the cyclic development of eggs every month. As a woman's eggs become less capable of producing a pregnancy, the levels of follicle stimulating hormone begin to rise. Therefore, FSH generally increases in women as they get older. Women who have gone through menopause have very high levels of FSH. This can be determined via simple blood test. The blood should be drawn on the third day of the menstrual cycle. What are the normal levels?
- Normal level for FSH on day 3 is less than 7 IU.
- Levels between 7 and 12 are considered elevated but women with such levels have been able to achieve pregnancy.
- Women with levels consistently over 12 have an extremely poor chance of achieving pregnancy.
What does a semen analysis analyze?
The complete semen analysis includes:
- Volume of the semen
- Sperm count (the amount of sperm in a certain volume of semen, also known as the sperm concentration or sperm density)
- Sperm size and shape (morphology)
- Sperm motility (percentage of actively moving sperm)
Normal findings are:
- Volume: 3 milliliters (2 to 6 mL range considered normal)
- Concentration: 20 million sperm or more per milliliter
- Motility: 50% of sperm still active after two hours
- Normal forms/appearance: 60% of the sperm
- Viscosity - ejaculate normally liquefies within an hour
- pH: 7 to 8
Treatment of infertility
Medications
Many physicians use fertility medications to try to increase the chance of pregnancy. These medications should increase the number of eggs that develop in a given month, thus enhancing the chance that at least one of them gets fertilized and develops into a viable pregnancy.
In-vitro fertilization (IVF)
Others have advocated in-vitro fertilization (IVF) as a mean to achieve pregnancy in cases of infertility.
Unfortunately, the pregnancy rates with IVF in women over the age 40 are very low.
Currently, the only consistently successful method to improve pregnancy rates in women with age-related infertility is egg donation. The indications for egg donation include:
- Age over 40
- Persistently high FSH levels at any age -- Poor response to fertility medications at any age -- Poor egg quality IVF
- Age-related recurrent miscarriage
Tips for enhancing reproductive health
Stop smoking
It is proven that tobacco smoking is linked to low sperm counts and sluggish motility. As a matter of fact, recent findings suggest that there is a 64% increase in miscarriage when both partners smoke or the man smokes.
Give up marijuana
Long-term use of marijuana in men results in a low sperm count and sperm that exhibit abnormal patterns of development.
Quit with alcohol
Chronic alcohol abuse damages the intricate plumbing of the male reproductive system, reducing a man's ability to produce normally formed sperm cells.
Exercise
Men who exercise excessively may be reducing their sperm count due to the heat that builds up around the testicles during strenuous exercise.
Check into your antibiotics
Some groups of antibiotics have been shown to affect sperm quality temporarily by decreasing count and motility. These groups are nitro-furans (nitrofurazone or nitrofurantoin) and macrolides (erythromycin).
Good nutrition
If a person is malnourished or not getting enough of the right foods and nutrients, sperm count may suffer.
Keep your scrotum cool
Excessive heat in the scrotal area should be avoided at all costs. Hot tubs, saunas or anything that raises the temperature of scrotum, including overheated vehicles and hot work environments should be avoided.