Our life expectancy is now higher than ever. How about fertility?
BIOLOGICAL CLOCK ANDÂ LIFE EXPECTANCY
It has been increasing to the highest point in history – reaching +61% between 1950 and 2015. Since studies show that the maximum human lifespan is estimated to be around 126 years, there is still room, around 40 years, that the life expectancy can continue to climb.
Life Expectancy from 1950Â [2] to 2015Â [3]
| Japan | France | Australia | United States | |||||
| Year | Male | Female | Male | Female | Male | Female | Male | Female |
| 1950 | 57.6 | 60.9 | 63.4 | 69.2 | 66.5 | 71.8 | 47.9 | 50.7 |
| 2015 | 80.5 | 86.8 | 79.4 | 85.4 | 80.9 | 84.8 | 76.9 | 81.6 |
| +40% | +43% | +25% | +23% | +22% | +18% | +61% | +61% | |
On the societal front, there is a concurrent phenomenon where women are deferring the delivery of their motherhood at increasingly older ages: the mean age being as late as 29.5 years in 2014 compared to 23.1 years in 2000 in the United States. Does the increasing lifespan positively prolong the biological clock too?
For current statistics, the average age of motherhood ranges from 21-26, while for fathers, the age has increased to 27-31 years. A survey indicated that the top reasons for the delay include financial insecurity, lack of an involved partner, and a home for raising a child.
The physiological and biological aspects of our body have not evolved advantageously along with the increasing life expectancy. This is worthy of attention, particularly when it comes to the reproductive function for women – the female reproductive biological clock would stop ticking at the time of menopause regardless of how long the person will live.
Women’s Age and Pregnancy-Related Complications.
With advancing age, there is also an increase of having pregnancy-related complications. They are;
- Gestational diabetes.
- Placenta Previa (cervix is totally covered behind the placenta, increasing the incidence of placenta detaching).
- Risks of miscarriages.
- C-section and stillbirth possibility.
- Endometriosis and PCOS (Polycystic Ovarian Syndrome).
Women become sterile 10 years before menopause.
Some studies showed that the mean age of menopause is 51 years, and women become sterile 10 years before menopause (last birth at 40.6 years). Meanwhile, a woman usually reaches menopause 6-7 years after having an irregular menstruation cycle.  This means that women can be sterile, around 3-4 years, before the complete cessation of the menstruation cycle.
Menopause is a consequence of reproductive aging and follicular depletion (ovarian failure), yielding biologically disadvantageous metabolic alterations accelerating several age-related health conditions: osteoporosis, cardiovascular disease, and cognitive decline. It is, therefore, to a woman’s advantage to have menopause later than earlier for reproduction and well-being reasons, especially with an anticipated increasing life expectancy. Women’s fertility begins to decline gradually but considerably around 32 and then accelerates after 37.
Click here to find out what menopause is and what you can do about it.
Women’s age-related decline in fertility comes after 30 while men start 40-45 years .
As we age, ovarian aging – women’s oocyte/follicle pool depletes in terms of quality and quantity – causes most embryos from women at or above 40 years of age chromosomally abnormal and rarely develop further.
| Women’s Age | Live Birth Rate |
| <30 years | 24% |
| 40-44 years | 8% |
| 45 years or above | 3.5% |
Age-related infertility for women is reflected by:
- The probability of conception.
- Early termination of pregnancy after conception: embryo loss, pregnancy loss, fetal loss, spontaneous abortion, miscarriage, etc.
| Women’s Age | The % of non-conception after 1 year of attempt |
| 15-24 years | 6% |
| 35-44 years | >30% |
Until the very late stages of reproductive aging, most endocrine and sonographic cycle characteristics remain more or less normal. The first endocrine sign of reproductive aging is a rise in FSH levels at age 35-40.
| Endocrine | Implication |
| FSH | Rising and very high can be a risk indicator for Down’s conception and an almost exhausted ovarian follicles pool.
The rise can occur between 35 and 40 years of age |
| LH levels | Rise with age, much later than FSH |
| Estradiol | No appreciable changes with age unless the menstrual pattern is irregular |
| Progesterone | No appreciable changes with age unless the menstrual pattern is irregular |
Quantity of oocytes/follicles decreases as one ages
Studies established that the optimal age of conception lasts until the age of 31. From the mid-30s, fertility drops sharply – at age 38, it is dropped to 1/3 of that in 30-or younger women.
| Stage | Reserve of Follicles / Oocytes |
| Before birth | Millions of follicles |
| puberty | ~300,000 follicles
–Â Â Â Â Â Â Â hundreds vanish monthly (during periods, pregnancy, breastfeeding, use of oral contraceptives) |
| 45-46 years | A few thousand (around 1/10 of puberty)
–Â Â Â Â Â Â Â resting follicle pool is almost exhausted at 46 years |
| ~51 years/menopause | < 1,000 follicles |
Effect of decreased quality of oocytes
Besides the number of follicles, the quality of oocytes decreases in parallel after the optimal age of conception (18-30 years of age); the quality control of follicles in older women is also reduced.
Most embryos are chromosomally abnormal in women after 37 years old with combinations of monosomies and trisomies (chromosomal disorders such as Down syndrome, Edward syndrome and Patau syndrome, etc.).
- The risk of giving birth to a child with Down’s syndrome and other numerical chromosome abnormalities rises as maternal age after 35.
| Women’s Age | % of Early Pregnancy Loss |
| 20 years | ~50% |
| 40 years | 96% |
Older women can still conceive, but the probability of yielding live births is lower because of pregnancy loss – the natural death of an embryo or fetus before developing further.
Most pregnancy loss occurs non-detectable at the expected menstruation and thus remains unnoticed – 80% happens within the first 12 weeks of pregnancy. Chromosome studies on spontaneous abortions showed frequent pregnancy loss because at least 80% of trisomy 21 embryos spontaneously abort.
The combination of both partners’ ages determines the likelihood of pregnancy.
Aging Effects on Men’s Fertility :
Fertility in males does not end as abruptly as it does in women. This does not, however, imply that men’s fertility is unaffected by their age. Male fertility is affected by various variables that are currently unknown, even though much literature is available for studies for women’s fertility. Some of the factors that affect male fertility can be listed below.
- Decreased amount and motility of sperm produced.
- Increased number of abnormal pregnancies due to a mutation in genetic makeup.Â
- Increased chances of genetic abnormalities such and neuropsychiatric disorders such as schizophrenia, autism, and bipolar disorders.
- Increased possibilities of miscarriage.
Marcus Bishop suggested in his review that pregnancy loss should be regarded as an unavoidable and necessary mechanism to eliminate unfit genotypes in each generation.
Despite this logical comment, the loss of an infant through stillbirth, miscarriage, or neonatal death is recognized as a traumatic life event. It has a large psychological impact on the mothers, fathers, and the relationship of a couple. Psychotherapy ensuring ongoing dialogue between the grieving parents is highly suggested to avoid any decline in the quality of a relationship after pregnancy.
Click here to see if freezing an egg is a viable alternative for delayed motherhood.
References:
[1]  H. J. Jung e M. W. Byung, «Theoretical estimation of maximum human lifespan,» 17 June 2008. [Online]. Available: https://link.springer.com/article/10.1007%2Fs10522-008-9156-4. [2]   National Research Council (US) Panel on Understanding Divergent Trends in Longevity in High-Income Countries, «Explaining Divergent Levels of Longevity in High-Income Countries,» 2011. [Online]. Available: https://www.ncbi.nlm.nih.gov/books/NBK62373/. [3]   «World Health Statistics 2016: Monitoring health for the SDGs,» 2016. [Online]. Available: http://www.who.int/gho/publications/world_health_statistics/2016/Annex_B/en/. [4]   T. Mathews e B. Hamilton, «Mean Age of Mothers is on the Rise: United States, 2000–2014,» Centers for Disease Control and Prevention, January 2016. [Online]. Available: https://www.cdc.gov/nchs/data/databriefs/db232.pdf. [5]   J. Daniluk e E. Koert, «Between a rock and a hard place: The reasons why women delay childbearing,» 2017. [Online]. Available: http://sciedu.ca/journal/index.php/ijh/article/view/10914. [6]   E. Velde e P. Pearson, «The variability of female reproductive ageing,» [Online]. Available: https://watermark.silverchair.com/080141.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAAbkwggG1BgkqhkiG9w0BBwagggGmMIIBogIBADCCAZsGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMRyVFcMHuS_8VlPIXAgEQgIIBbCBvvKNUUdfeYM8BfpsET4KmYTMXb6exhpADABlQvczEtZBG. [7]   J. Hurt, M. Guile, J. Bienstock, H. Fox e E. Wallach, «The Johns Hopkins Manual of Gynecology and Obstetrics,» 2011. [Online]. [8]   M. Bishop, «Paternal Contribution To Embryonic Death,» 1964. [Online]. Available: http://www.reproduction-online.org/content/7/3/383.short. [9]   A. Kersting e B. Wagner, «Complicated grief after perinatal loss,» June 2012. [Online]. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3384447/. [10] R. Pollycove, F. Naftolin e J. Simon, «The evolutionary origin and significance of Menopause,» March 2011. [Online]. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3433273/.
