Like a Virgin by Prasad, Aarathi (recommended reading txt) 📕

a cacophony. But it is the eggs and their corrupt chromosomes that are most at fault. When an older woman is implanted with young eggs – even just the cytoplasm, that cellular soup inside an egg minus its DNA – they become pregnant, despite all of the other changes going on in the body. In fact, older women actually stand a better chance of becoming pregnant with donated young eggs than younger women do of conceiving naturally.

Something doesn’t seem quite fair about these facts of fertile life, when you start to think about them.

It has long been reasonably obvious that for women, age is the main factor in the loss of fertility. But matters are less clear when it comes to men. In contrast to women’s reproductive ability, male functions do not cease so abruptly – there is no single event that parallels the menopause. This means that throughout their lives, men continue to produce sex hormones and to generate sperm. And yet, the effects of paternal age on a couple’s fertility are significant.

A healthy couple in their mid-twenties has only a twenty to twenty-five percent chance of establishing a ‘natural’ pregnancy in a given month, while a couple aged forty can only match that chance through the use of IVF and other techniques. Because older women tend to have male partners who are around the same age as them, or older, older couples also carry the added risk from the greater number of genetic mutations that occur in the sperm of older men – the curse of corrupt chromosomes.

It is now understood that having a male partner over forty years old is an important factor in failing to conceive, and when a man is over fifty, there is also a significant decrease in how many embryos form properly and how many babies are born alive. If a woman’s male partner is over thirty-five, there is a higher risk of seeing the pregnancy end in miscarriage than for those whose partners are younger, regardless of the woman’s age. If the pregnancy succeeds, sperm-based mutations may lead to a range of lifelong conditions. Autosomal dominant diseases, such as short-limbed dwarfism (achondroplasia) and Marfan syndrome, affect connective tissue and can cause problems in the skeleton, eyes, heart, blood vessels, nervous system, skin, and lungs. Some genetic disorders that arise as fathers get older behave a bit like a jammed CD, with sequences of the DNA code repeating when they shouldn’t. These conditions include Fragile X syndrome, the most common cause of inherited mental impairment; myotonic dystrophy, a disorder of the muscles and other body systems; and Huntington’s disease, a currently incurable condition that causes deterioration and gradual loss of function in the brain.

When it comes to making babies, time is not on our side, whether you are dealing with egg or sperm. While the link between age and infertility is certainly biological, some people are infertile early or throughout life. Leaving the decision to have a baby until the thirties or forties means that the underlying cause of a person’s infertility won’t be identified until it may be too late to identify or correct. That is to say, most people won’t find out they’re infertile until they start trying, whenever that is. Around one in six couples who cannot establish a pregnancy on their own will seek medical assistance, and the average age for receiving IVF procedures in the UK is thirty-five. Sometimes the problem is a minor one, but that is not always the case. For around one quarter of people who find they cannot get pregnant, the problem cannot be pinpointed at all – the dreaded ‘no diagnosis’. Slowly but surely, scientists are uncovering what may be behind these mysteries.

There is a growing list of genes that have been found to be key players in regulating when a woman is fertile and when she is sterile.

A gene on the X chromosome, FMR1, for example, is coming into use as part of a genetic test that aims to predict the rate at which a woman’s egg supply is running out. FMR1 is known to help regulate the transition of eggs from immaturity to maturity. The sequence of chemicals that spell out the FMR1 gene contains repetitions, and women with a version of the gene that contains more than two hundred repeats of the DNA sequence CGG are likely to have Fragile X syndrome. But there are also women who have fifty-five to two hundred CGG repeats – not quite enough to disturb the gene and cause mental impairment, but enough to put the carrier at increased risk of experiencing an early menopause. If a woman has between twenty-eight and thirty-three repetitions this leads to abnormal levels of anti-Müllerian hormone, or AMH, which fluctuates throughout life. Healthy women with low levels of AMH for their age seem to hit menopause earlier; they also have fewer eggs, lower fertilization rates (whether through ‘natural’ means or IVF assistance), generate fewer embryos, and have a higher incidence of miscarriage during IVF transfers. Women with insufficient AMH have half the number of successful pregnancies compared with women with high AMH levels. In fact, AMH levels are usually a better tip-off than a woman’s age in guessing how successful IVF will be, ranging from how many eggs will be harvested from her ovaries to whether she may miscarry once an embryo is transferred from a Petri dish to the womb.

But FMR1 is not the only genetic clue to a woman’s fertility. It appears the BRCA1 gene mutation – widely known for its role in breast cancer and ovarian cancer – may offer information about the risk of premature ovarian ageing. Normally, BRCA1 rallies other genes in the cell to repair damaged DNA. When the BRCA1 gene itself is damaged, or when damage accumulates on