How is Fertility Linked to Parental Age?
- Posted on: Aug 29 2014
Modern societal demands have led couples to delay their child-bearing age into the 30s and 40s. It is known that fertility of a woman declines with her age. Thirty five years is the typical timeframe for women, after which risks of infertility, pregnancy complications and fetal abnormalities tend to rise. The effect of paternal age on fertility is, however, not clearly established. Moreover, it is often difficult to isolate male age-related fertility problems, because most of these cases are associated with advanced female age as well. This article summarizes key medical findings on parental age-related concerns for fertility.
A female is typically born with 1 – 2 million oocytes, and the loss of oocytes occurs consistently throughout a female’s life. By puberty, an adolescent female is left with 300,000 – 500,000 oocytes, and by the time of menopause only a few hundred of oocytes remain. A decrease in the ovarian follicle reserve in women is associated with diminished fertility. Clinical signs of age-related decline in fertility are shortened menstrual cycles and irregular menses.
A woman’s advanced age also takes a toll on her oocyte quality. Studies on IVF cycles have demonstrated higher oocyte DNA abnormalities with age.
According to population studies, after 35 years of age for women there is a decrease in birth rate. The decline in fertility seems to be related to reduced ovarian function with age. Uterine capacity, however, is not similarly affected. Therefore, donor egg IVF cycles lead to positive outcomes in women of advanced years.
Spermatogenesis, or the development of sperm cell, takes place continuously in the adult male. Unlike oogenesis (the production of female eggs), which takes place only during fetal development, human sperm cells are being formed even in elderly men. Therefore, with advanced age, the opportunity of errors during DNA replication tends to increase, leading to defects in sperm DNA.
Semen Attributes: Studies have shown that 50-years old men tend to have lower semen volume, decreased sperm motility and reduced percentage of normal sperm cells compared with those from 30-year old men. However, one has to bear in mind that these sperm parameters do not perfectly correlate with the fertilizing ability of the male.
Urological and prostate disorders in men can also have a detrimental impact on fertility. The medications for treating these conditions can enter into the seminal fluid, and adversely affect a pregnancy.
Infertility issues, such as erectile dysfunction, decreased libido and ejaculation capacity, can also affect men as they age. Surgeries in the male reproductive tract can lead to scarring and further reduce fertility. Likewise, cancer treatments for bladder and prostate cancer can decrease one’s ability to ejaculate, thereby necessitating the aspiration of semen directly from the testes.
The use of testosterone supplementation can reduce sperm count, and men trying to start a pregnancy should avoid such supplements.
Other Studies: Studies comparing IVF outcomes in different age groups of men have found that advanced age is associated with fewer blastocyst embryos, decrease in live birth and an increase in spontaneous miscarriages. Various other studies have found an association of advanced paternal age and increases in birth defects, C-sections, pregnancy-induced hypertension, preterm labor, placenta and low birth weight babies.
In conclusion, it can be said that both partners need to be aware of the risks of subfertility and pregnancy complications after the age of 40 years.
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