Did you know that women are born with approximately 2,000,000 eggs? By the time of the onset of their first period this number is reduced to approximately 300,000, and your egg numbers will continue to fall until menopause.
Did you know that there is also an increase in the rate of the production of your ovaries to release an egg each month? This increases from the age of 37.5 years until menopause.
Your asking the question what does this mean? This means that the likely hood of a normal good quality egg released each month reduces, meaning that there is a reduced number of overall eggs that will be released that have the ability to fertilise normally, it can also increase the rate of miscarriage.
In a study by Marcus and Brinsden 1996, they found that age in women was associated with decreased embryo viability, meaning the quality of the eggs and embryos to make a baby reduces. Fertility support for men & women is needed for the best results
Embryo quality is influenced by the egg maturity when it is released from the ovary, and this is determined by the biology of the egg and the environment it’s produced in.
It is thought that the lining of a women’s uterus isn’t the issue when she gets older and trying to fall pregnant, but the quality of her eggs that are released each month.
In a review by Ziebe et al., 2001 they found that high pregnancy rates in older women with donated eggs from younger women, showing that age is related to the egg quality.
In a study by Garrido et al., (2000), they found that women that suffered endometriosis also had lower quality eggs and embryos. This is thought to be to do with an increase in reactive oxidative species ROS in the fluid found in your fallopian tubes.
What is ROS you ask? It is an unstable molecule that contains oxygen that easily reacts with other molecules in the cell, causing cell damage.
Embryo quality: Age and Miscarriage
Embryos undergo a process during development called fragmentation, this is whereby parts of the developing embryo’s cell breaks off and are separate from the main body of the embryo. This is a very common process but it depends on the degree of this fragmentation that depends on the quality and the development of the embryo.
In a study by Ziebe et al., (2001) they found that there was no real difference what is known as the fragmentation rate for women under the age of 40, but once they reached 40 and over, the embryo fragmentation rate rapidly increased, this also correlated with a significant decrease in embryo implantation in women over 40.
In a study by Ziebe et al., (2001) they found that embryos at the days 2 & 3 stage of development that were transferred in women aged over 40, showed a significant decrease in the implantation rate.
What does this mean? This means that even though the embryo grade and quality looked, to the naked eye, structurally as good as an embryo from a younger woman, there was a decrease in the embryo quality with an increase in the age of a women ovary age.
Scientists have also documented that in day 5/6 embryos as a woman gets older there is a decrease in quality of the embryo at this stage the older the lady.
This leads to a lower percentage of embryos reaching the day 5/6 stage, and with a decrease in the quality of embryos all round. With out taking a women’s age into account, Ahlstöm et al (2011), found that there was a greater chance of pregnancy with day 5 embryos that were the grading of 4BA or 3BA.
Embryo quality: Age and genetics
As women age, their eggs begin to decrease in quality and quantity. Women aged 37 years and over face a higher risk of embryos that have the incorrect genetic programming, such as Down’s syndrome and can cause spontaneous miscarriage.
In younger women, the structures within the egg cell are generally more normally organised at the developing egg.
Women aged 37 years and over have been found to experience more spontaneous miscarriages that are genetically abnormal in the majority of cases.
According to a range of literature and studies, this is due to deterioration in the development process of the egg that occurs with age.
Ford (2013), found that women over 37 showed a decrease in some normal genetic structures in the egg.
Instances of Down’s syndrome have been found to increase with the age of both male and female partners, it is caused by an extra chromosome in the embryo. The extra chromosome that causes Down’s syndrome is approximately 80% from maternal origin and 20% paternal origin.
For a woman aged around 20 years, the risk of Downs’s syndrome is 1/1667. The risk increases to 1/30 around the age of 45 years.
Allen et al., (2009) found in their large population-based study that there was a correlation between older women and the extra chromosome within the eggs. The study found that there was a higher incidence of genetic errors for women ≥40 years of age at the time of their baby’s birth.
Allen, E. G., Freeman, S. B., Druschel, C. O’leary, L. A., Romitti, P. A., Royle, M. H., Torfs, C. P., Sherman, S. L. (2009) ‘Maternal age and risk for trisomy 21 assessed by the origin of chromosome nondisjunctions: a report from the Atlanta and National Down Syndrome Projects.’ Human Genetics 125,1, 41-52
Ahlstöm, A., Westin, C., Reismer, E., Wikland, M., Hardson, T (2011) ‘Trophectoderm morphology: an important parameter for prediciting live birth after single blastocyst transfer.’ Human Reproduction 26:12, 3289-3296
Ford., J. H. (2013) ‘Reduced quality and accelerated follicle loss with female reproductive aging – does incline theca dehydroepiandrosterone (DHEA) underlie the problem?’ Journal of Biomedical Science 20, 93, 1-9
Heffner., L. J. (2004) ‘Advanced Maternal Age – How Old is Too Old?’ New England Journal of Medicine 351,19
Marcus., S. F. and Brinsden., P. R. (1996) ‘In-vitro fertilization and embryo transfer in women aged 40 years and over.’ Human Reproduction 2, 6, 459-468
Yoon., P. W. Freeman., S. B. Sherman., S. L. Taft., L. F. Gu., Y. Pettay., D. Flanders., W. D. Khoury., M. J. and Hassold., T. J. (1996) ‘Advanced Maternal Age and the Risk of Down Syndrome Characterized by the Meiotic Stage of the Chromosomal Error: A Population-Based Study.’ American Journal of Human Genetics 58,625-633