Can Getting Pregnant Again at 9 Months Really Degreas You Lifespan

How far can female fertility be extended?

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Modern medicine is already allowing women to have children far later in life than their ancestors, but how far can female fertility actually be extended?

"Information technology'southward one of nature's peachy inequities," says Dagan Wells, professor of reproductive medicine at the University of Oxford. He is referring to the progressive, and largely irreversible, decline in female fertility from the age of 35 years onwards.

Men also feel a decline in their baby-making ability as they become older, just this fall in fertility tends to start after and occur much more than slowly than in women. The fertility charge per unit for men tends to begin falling around the age of 40-45 years old.

Just when exactly does a woman's fertility first declining? And when does that reject issue in the end of natural fertility?

For millennia, women have been getting pregnant and bearing children in their teens and early 20s – not much unlike from the Krapina Neanderthals, living in Northern Croatia xxx,000 years ago, whose fossilised remains suggest gave nativity to their offset child at 15 years of historic period. Prior to the 1960s, women in the US were having their beginning child on average at effectually the historic period of 21.

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In 2017, however, the average age of mothers giving nascence in all OECD countries was 30. Just nether half (44%) of all live births in England and Wales in the same twelvemonth were to mothers anile 30 while the boilerplate age of women giving nativity to their first child in S Korea was 31.

Fertility treatments and the ability to freeze eggs has immune more women to have children later than was possible in the by (Credit: Science Photo Library)

But what does this mean in the context of the ticking clock of female fertility?

Numbers matter

For decades, scientists have associated the turn down in female fertility with the historic period-related decrease in the number of eggs contained within a woman's ovaries. Each, if fertilised, has the potential to grow into a baby.

Different men, whose reproductive organs produce millions of fresh sperm on a daily basis, women are born with all the eggs that they will ever possess. Moreover, this number steadily declines as a adult female ages: from ane one thousand thousand eggs at nascency to 300,000 by puberty, 25,000 by the age of 37 and 1,000 by the historic period of 51. Of all these, however, but 300 to 400 eggs with baby-making-potential – normally merely one a month – will mature and somewhen be released from a woman'southward ovaries through ovulation across her unabridged life. For reasons non yet fully understood, the rest undergo a natural process of degeneration and will never be ovulated.

Most girls brainstorm menstruating between nine and thirteen years of age, simply their ovaries don't start releasing eggs until a least a year or two later. Uncomplicated mathematics would advise a woman's egg supply would and then typically exhaust itself around 33 years later. And in almost women, fertility does indeed tend to cease up to eight years before the onset of menopause, which for American women is around the time of their 51st birthday.

While such crude calculations do not have the natural variability that can be between women into account, or the time windows during which ovaries might release more than than one egg in a calendar month, or months in which no egg is released at all, they tin can give a crude guess of but how long the female person fertility timeline tin be.

A more precise judge of a woman'south egg count, too known as "ovarian reserve", tin can be obtained by measuring the level of hormone called anti-Mullerian hormone (AMH) in a woman'south blood. We now know that AMH, produced by the ovaries of fertile, developed women, plays a vital part in the metamorphosis of an immature egg cell into a mature, hopeful egg, consummate with all the biological prerequisites to create a healthy baby. Better functioning ovaries, with larger egg stores, produce more than AMH.  Levels of the hormone decline as the timeline of female fertility progresses – average levels in 30 to 35 twelvemonth olds are roughly ii-thirds that of younger women while levels in women anile over 45 years are a quarter of those seen in women in their 20s.

When they are born, women's ovaries already contain all the eggs they will always produce (Credit: BBC)

Andrea Jurisicova, an embryologist at the Lunenfeld-Tanenbaum Research Institute of Mount Sinai Hospital, has spent years studying the mechanisms that underpin the reject in female fertility with age, and investigating what can exist washed to boring this. Her research has constitute that ovarian reserve is genetically regulated just that a woman's life experiences – such as stress, exposure to radiation or toxic chemicals and even those from when she herself was in the womb – determine egg numbers in later life.

Quality matters

But female fertility isn't but about the quantity of eggs. Quality matters too, and is much more technically challenging to appraise than egg numbers. While egg counts decline as women historic period, so does the quality of the chromosomes and the Dna contained within each egg.

"Chromosomal abnormalities in human eggs are extremely mutual," says Wells. "Information technology's not something that should be considered to exist a especially aberrant situation, and in about cases its something that all women, even young women, will take in their eggs at a depression level just that level increases with advancing age."

For a woman in her 20s, a quarter of her eggs may be expected to have chromosomal abnormalities – this increases to upwardly to 40% for a woman between thirty and 35, and "goes upward simply exponentially from there on". Across the age of 35, the frequency of these chromosomally abnormal eggs increases past 0.5% per month, then that for a woman in her early 40s up to three-quarters of her eggs will have chromosomal abnormalities.

Having chromosomal abnormalities in her eggs doesn't necessarily mean a woman is infertile, simply they do mean that more than of her menstrual cycles will produce eggs that are less likely to produce a viable baby.

Chromosomes are bundles of tightly coiled Deoxyribonucleic acid that hold the genetic information needed for an organism to develop. A homo egg contains 23 chromosomes – the half of your genetic code that comes from your mother – which needs to combine with the 23 chromosomes from your father'southward sperm to develop into a feasible embryo. An egg with too many or also few chromosomes, broken or damaged chromosomes will often fail to develop properly. In some cases a babe tin still be born with chromosomal abnormalities, as happens with Down's Syndrome.

Merely nearly chromosomal abnormalities tend to be lethal to the extremely immature embryo, resulting in the embryo failing to implant in the lining of the womb or a very early miscarriage, often betwixt five and eight weeks of pregnancy.

While the chance of chromosomal abnormalities is known to exist higher in the eggs of older women, a recent European written report found that the level of chromosomal abnormalities is also high in younger women too – from 13 into their early 20s. The findings suggest that female fertility timeline follows a n-shaped pattern, with peak fertility observed in the mid-20s and lower levels of fertility both in very young and older women.

Older mothers may face greater risks during pregnancy, labour and delivery, but at that place are problems associated with older fathers too (Credit: Getty Images)

Elsewhere in the egg, faulty mitochondria – the tiny power stations that provide energy for our cells and which nosotros all inherit from our mothers – can also be a problem in older women. Studies have shown that upwardly to half the eggs of women who are older than 35 carry mutations in their mitochondrial DNA, compared to a third of the eggs in younger women.

"An egg needs a threshold of about 40,000 mitochondrial DNA copies to make an embryo," says Jurisicova.

For Wells, the evidence is articulate.

"The rate of decline accelerates around the age of 35 and the vast bulk of women are essentially infertile by the time they achieve 45," says Wells. "Chiefly, this is years, maybe even a decade, before menopause. Anybody expects to be a piddling less fertile when yous are older, but the extent of that pass up takes a lot of people past surprise."

It would be wrong to focus but on female fertility. Some studies take shown that sperm quality also declines with historic period in men, starting in their 20s. Sperm mobility – the ability of it to swim around – has been found to turn down by effectually 0.7% every year while the sperm of older men comport more mutations in their Deoxyribonucleic acid. Older fathers as well laissez passer on more mutations to their children than mothers practice from their eggs.

Best egg

"The human egg is a remarkable and unusual cell, it's the biggest prison cell in the trunk, and has a unique characteristic," says Wells. He is referring to the egg's ability to stop halfway through its growth and remain in a state of suspended animation for years, even decades, until it is eventually ovulated. His research suggests that it is the egg'south ability to concord its chromosomes in a stable configuration during this period of hibernation that governs its ability to make an embryo and a baby.

Jurisicova's work adds another slice to the puzzle. Her work suggests that human being eggs undergo a process of growth and maturation within the ovary for at to the lowest degree nine months before they are released during ovulation. "The quality of the egg released is the culmination of all the health and environmental influences on that growing egg over the by nine months," she says. Stress, exposure to radiation or toxic chemicals during this time tin have an adverse effects on the developing egg.

It is perhaps interesting that the duration of this incubation period – from when an egg emerges from hibernation and begins developing – uncannily resembles the number of months a infant spends within the womb before it is born. During this period of maturation, the egg develops the resources it volition need should it be fertilised.

"The egg has to be extremely well resourced," says Wells. "For the beginning three days post-obit fertilisation the embryo doesn't really make anything for itself – it doesn't transcribe its genes, it doesn't make proteins – its completely reliant on what the egg has provided for information technology. A more than mature egg is more likely to be amend resourced than a less mature ane."

While in that location may exist picayune that science can practise to change the number of eggs that nature (or genetics) decides a adult female will have during her life, Wells and Jurisicova agree at that place are ways to improve, or rescue, egg quality. Adopting a healthy lifestyle, exercising regularly, reducing stress and making sure that health bug such equally hypothyroidism and other autoimmune conditions are well controlled tin all help.

The range of factors pitched against an egg being fertilised and developing into a foetus make childbirth seem all the more than incredible (Credit: Scientific discipline Photograph Library)

Jurisicova recently institute that giving female mice the antioxidant coenzyme Q10 delivers promising results – the mice that received the supplement produced ameliorate quality eggs with more than properly aligned chromosomes and better mitochondrial part. They were also more than successful in producing alive babies, than the mice that did non receive the supplements. The results are, however, still to exist replicated in humans.

The journey, not the destination

Mothers don't just need to fence with their fertility as they get older, but also greater risks during pregnancy, labour and delivery. The First and 2nd Trimester Evaluation of Take chances (Faster) trial, a US study funded past the United states of america National Institute of Child Health and Homo Evolution (NICHD), looked at the wellness records of over 36,000 women. They constitute mothers over twoscore were two to three times more likely to feel health issues during pregnancy including diabetes and high blood pressure level. They were twice as probable to feel bleeding from their placentas, have a caesarean delivery and to lose their baby later on in pregnancy.

The children of older first-fourth dimension mothers who are 40 years and in a higher place also have an increased risk of health bug at birth, such as low nascency weight and congenital abnormalities. They also have a l% increased run a risk of being born preterm and, maybe consequently, are at increased adventure of requiring neonatal intensive care subsequently nativity.

But this is still only one half of the equation. Older fathers too bring additional health risks for their children. Babies with older fathers are more likely to be born prematurely, have a lower nascence weight and college run a risk of seizures. Some studies accept also linked increasing paternal age to a greater adventure of conditions such every bit autism and ADHD where the male parent is over the age of 40, but the bear witness remains inconsistent.

Scientists are developing new techniques to identify the all-time eggs for use in IVF treatments (Credit: Scientific discipline Photo Library)

Is information technology possible to extend female person fertility and for how long? As is often the instance, where nature creates inequity, science attempts to level the playing field. In September last year, Erramatti Mangamma, a 74-year-erstwhile from southern India become the globe's oldest first-time female parent, delivering twin infant girls conceived via In Vitro Fertilisation (IVF) after 57 years of infertility. 3 years agone, 72-year-old Daljinder Kaur, from north India, gave nascence to a son after about five decades of union and 2 unsuccessful IVF attempts.

The meaning advances in reproductive medicine over the past decades have greatly increased the safety, success, accessibility and affordability of artificial reproductive techniques. Approximately 230 babies are born in the UK each twelvemonth to women anile 50 and over while 9% of all showtime-fourth dimension mothers in the United states were anile higher up 35 in 2014.

But as we take seen, these techniques are all the same limited to a degree by the age of the egg. This is, not least, because of the furnishings of ageing on the Deoxyribonucleic acid, but also because older eggs have been exposed to environmental toxins for a longer amount of time. It is possible, of course, for women to undergo IVF using a donated egg from a younger woman. Nearly all fertility clinics across the earth at present also offer women an option to store their eggs, frozen in time, until she is prepare for them to be thawed, fertilised and transplanted into her womb.

"The difficulties experienced with older women trying to accept children is not related to the uterus just to the egg, and chromosomal abnormalities are at the heart of that," says Wells. "The egg is the seed rather than the soil. Many of the very early steps in human development are adamant by what the egg provides."

With the help of technologies like pre-implantation genetic testing, Wells and his boyfriend embryologists are developing ways of identifying the all-time eggs that can be used in IVF treatments. Other techniques such as mitochondrial replacement therapy are also helping mothers with defects in their eggs give birth to healthy children.

Merely while scientific discipline is making commendable steps to assistance prolong the ticking clock of female person fertility, it may non ever be possible to proceed it going indefinitely. The refuse of natural female fertility is as inevitable as it is universal.

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Source: https://www.bbc.com/future/article/20200828-how-fertility-changes-with-age-in-women

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