午夜福利1000集合

LAST year, I attended a conference about reproduction. The take-home messages were very clear. If you want children, you have to start early. Women think they can wait to have kids, but they can鈥檛. Older women who conceive are probably secretly having IVF or using donated eggs. And IVF isn鈥檛 as reliable as people think it is.

As a woman approaching 30, I couldn鈥檛 help taking this personally. Chatting about my concerns with one doctor at the conference only made matters worse. She gave me this advice: 鈥淒on鈥檛 worry about finding the perfect man 鈥� you鈥檝e got time to do that. Just focus on finding a good father for the time being.鈥� I鈥檒l admit it, my musings on my own fertility temporarily turned to panic.

I know I鈥檓 not alone. Across the developed world, people are increasingly choosing to delay starting a family. The reasons are complex and various, but as a result many women 鈥� and men 鈥� around my age are anxiously questioning their fertility. When should I start trying for a baby? How do I optimise my chances? Is it worth taking a fertility test? It鈥檚 surprisingly difficult to find answers. So I set out to look for some.

Is there a 鈥渞ight鈥� age to have a baby?

Men produce new sperm throughout their lives but women are thought to have a limited supply of eggs. In fact, the number peaks at the fetal stage 鈥� a 20-week-old fetus has about 6 million 鈥� and dwindles to around a million at birth. Some 300,000 eggs are left at puberty. around the age of 32 and is more rapid still from 37 until about 50 when menopause occurs (see chart). . Older eggs are less likely to be successfully fertilised, to implant in the uterus or develop successfully.

鈥淏eing in an expensive housing market delays first births by three to four years鈥�

According to the , . But in the developed world (see graphs). A woman in her 30s has about a 1 in 5 chance of getting pregnant each month she tries. That drops to about 1 in 20 in her 40s. And infertility usually starts four or five years before the menopause. At least that鈥檚 what the biggest population studies reveal. They were carried out decades ago before contraception was widely available and studies of natural fertility became very difficult to do. Things may have changed since then because fertility is influenced by many lifestyle factors, some of which have dramatically altered in the intervening years (see 鈥淲hy are some women more fertile than others?鈥�, below).

Still, older couples are more likely to have problems conceiving and face more problems during pregnancy and birth 鈥� even if only the male is older. Their children are also more likely to have a genetic condition. Women over the age of 40 have a 1 in 100 chance of conceiving a child with Down鈥檚 syndrome, which is more than three times as likely as for a 35-year-old, for example. Older fathers have a higher chance of having kids with schizophrenia, as well as disorders linked to single gene mutations, such as achondroplasia 鈥� a cause of dwarfism. Autism also becomes more common.

But there are also perks to being older parents. With age tends to come higher income and greater job security, so older parents are often better able to provide for their children. There is even evidence that postponing becoming a mother until after the age of 40 in terms of health and education. Older parents may be more secure in their relationships, too. And some studies indicate they experience less parenting stress.

Why are some women more fertile than others?

Aside from age, there are biological differences, but these are poorly understood. However, we do know that lifestyle matters. All the things you might typically associate with general well-being also have an impact on fertility. 鈥� even passive smoking 鈥� have been linked to a longer time to conception. . : women who have higher levels of an enzyme associated with stress in their saliva , for example. Then there are sexually transmitted infections such as chlamydia and gonorrhoea, which can cause physical damage that makes it harder to conceive.

Many common disorders can affect fertility too. Polycystic ovary syndrome, for example, is thought to affect around 7 per cent of women worldwide. Here, the follicles that surround the eggs can be unusually large or high in number, swelling the ovary and making it difficult to release the eggs properly. Nevertheless, .

Endometriosis, in which cells that should be in the uterus migrate to other parts of the body, can also influence female fertility. I must declare an interest here. Five years ago, when I had surgery to remove a rotten appendix, I awoke to be told that the surgeon had also removed a patch of endometriosis he鈥檇 found. Until then, I had no idea I had the condition. I鈥檝e since discovered that endometriosis often goes undetected, and we still don鈥檛 know what causes it, or the best way to treat it. Doctors can remove the offending tissue, but it can return. They often prescribe oral contraceptives and painkillers. Endometriosis affects around 1 in 10 women. It can and . It can also cause a great deal of fertility anxiety.

What factors influence a man鈥檚 fertility?

A man鈥檚 ejaculate can contain up to 1.8 billion sperm, which wriggle and writhe in their race towards the egg. Well, sometimes. For most healthy men, the figure is closer to 300 million. And most of these will have deformities that leave them unable to compete. In fact, the World 午夜福利1000集合 Organization states that a fully fertile man need only expect 4 per cent of his sperm to look normal.

Like women, men become less fertile with age, though it doesn鈥檛 have much effect until after 40 鈥� and many men father children into their 60s and beyond. Nevertheless, several factors can affect fertility in younger men. Obesity has been linked to erectile dysfunction and poor sperm production. . Smoking and drinking can have adverse effects too. And it is true that overheated testicles 鈥� whether from illness, a hot bath or a laptop 鈥� can temporarily lower sperm counts.

So if you are trying for a baby, it makes sense to eat well and exercise. But ignore the locker-room myths, advises of the University of Sheffield, UK. For example, he has heard men say they will 鈥渟ave up鈥� their sperm and abstain from ejaculating for weeks or months before trying for a baby. This isn鈥檛 a good idea. 鈥淚f you store it up, the older sperm can degenerate and damage the newer sperm,鈥� says Pacey. He recommends having sex regularly.

Read more: Should I take a fertility test?

Should couples curious to know the implications of postponing parenthood take a fertility test? Jessica Hamzelou and her boyfriend tried one 鈥� this is what they found out

Can I extend my fertility?

There are many reasons to put off starting a family. One study, for example, found that being in an expensive housing market delays first births by three to four years. Another report found that in 21 European countries were more likely to have their first child later. Whether from choice or necessity, many people are delaying parenthood. For women in particular, this means risking childlessness if they leave it too late. Can technology help by extending the reproductive window?

People are certainly making more use of it. In the US, the number of cycles of IVF and similar procedures . According to the latest statistics compiled by the US Centers for Disease Control and Prevention, more than 208,000 cycles of these assisted reproductive technologies were carried out in the country in 2014, . Recent research in Spain suggests that for women under the age of 35, some 41 per cent of IVF cycles are successful, which compares well with natural conception rates. However, the success rate falls to 23 per cent for 38 and 39-year-olds. And those who were 44 or older had only a 1.3 per cent chance of giving birth following a cycle of IVF. By comparison, the average woman in her 40s has a 1 in 20 chance of conceiving naturally each cycle.

IVF is clearly not a reliable way for a woman to extend her fertility. So what about egg freezing? Its promise, to allow people literally to put their family plans on ice, has been seized on by companies including Apple and Facebook, who started offering it to female employees a couple of years ago. One fertility specialist has even suggested that it would be the .

Egg freezing starts like IVF 鈥� women take rounds of hormone treatment that make them release a higher than normal number of eggs. These are surgically removed and stored in deep freeze. To date, an estimated 5000 babies have been born from frozen eggs. However, the technique (and its younger sister ovarian tissue freezing) has mostly been used to help women with cancer conceive after chemotherapy. We know little about its effectiveness in older women. What we do know suggests egg freezing is not a reliable backup for women wanting to delay parenthood. Success depends on the number of eggs obtained, how many survive freezing, and what proportion can make it through the thawing process. Then they鈥檝e got to be successfully fertilised, grow into a healthy embryo and manage to implant and survive in the uterus. There is a lot that can go wrong.

If technology is not the answer, there is still hope. New research suggests your ovaries can be rejuvenated using chemicals derived from your blood. But even without that, the risks of waiting to have a baby may not be as big as you think, provided you are healthy.

This article appeared in print under the headline 鈥淭he pregnancy pause鈥�