What are the Worldwide Trends in Fertility?

Are sperm counts really declining? And are we having families later in life?
21 March 2017

Interview with 

Professor Tim Child, Oxford Fertility


One in seven couples currently experience problems when trying to conceive; so the question is are fertility rates declining? Georgia Mills spoke to Professor Tim Child from Oxford Fertility...

Tim - There’s certainly some controversy, but it may be that male sperm quality is reducing - there’s some controversy around that. It’s certainly true that women tend to be leaving it later in life to be trying to conceive and so we’ve noticed quite a significant shift actually in age of first childbirth. And also there have been increasing rates of chlamydia and other problems that could affect the woman’s tubes.

Georgia - Is the fertility going down? Are we seeing this across the world?

Tim - Again, some controversy. From a UK perspective it can be difficult to work out. There’s increased awareness because, for instance, programmes such as this on fertility issues and potentially treatments for fertility. So certainly within the UK we are seeing that more people are coming forward and looking for fertility treatment.

Georgia - What about elsewhere in the world?

Tim - Again, in Africa for instance, there are data suggesting that infertility rates are increasing. Again, the difficulty is that there are such huge social changes going on around the world that it can be hard to know the extent to which changes are due to social changes or actual pathology affecting fertility.

Georgia - You mentioned earlier this might be due to people having children later in life. So how does this affect fertility?

Tim - As you mentioned in the intro, women are born with a couple of million eggs in their ovaries and for some reason, we’re not entirely sure why, the eggs that are released as women get older are more likely to have genetic or chromosomal problems within. They’re more likely to have the wrong number of chromosomes. The same is true for men as well but it happens at a later age. What that means is that on a monthly basis, as couples get older, they’re less likely to get pregnant and, unfortunately, are more likely to have a miscarriage.

Georgia - You can see this month by month?

Tim - Yes, certainly. So as you go through a woman’s reproductive life, and you look at her chance of getting pregnant year by year, then roughly up until her early 30s it appears to be fairly stable. But as she goes into her mid and late 30s then her monthly chance of conception does go down and the unfortunate double whammy is the chance of miscarriage does increase.

Georgia - What about other environmental factors that might be having an impact on impact on fertility rates? Do we have any possible suspects?

Tim - Well, I know that one of the later speakers is going to be focussing more on the sperm side of things, but there have been various environmental, perhaps chemical, suspects from a sperm perspective. The same is true from a female perspective, there’s been some suggestion that some chemicals may be increasing the risk of conditions such as endometriosis, which is a common condition that 20% of women have that can affect fertility. But again, the quality of sa lot of this data is very, very poor so we’re not entirely sure.

Georgia - There’s a lot of things out at the moment where we’re not eating very well, we may be a bit fatter than we should be. Has that been linked with fertility?

Tim - Certainly BMI has been linked with both male and female infertility. We know that  as a woman’s BMI increases after the 20s into the 30s, then her monthly chance of getting pregnant goes down, and again the chance of miscarriage does go up. We’re not entirely sure why, and this why, for instance, those people that are lucky enough to qualify for NHS IVF funding if they need it, in nearly all areas of the UK, women will have to have a BMI of less than 30, and that’s really based on the very strong evidence that BMI does matter.

Georgia - OK. So we’ll be probing a bit more about the male and female effects that might be causing this but, just briefly, what are people doing who are having trouble conceiving? What kinds of things are they doing to try and help them?

Tim - One of the most important things is if couples are worried about their fertility, then the first port of call would be to have a chat with the GP. That could be after 6 to 12 months of trying for instance. In general, if a woman’s having regular cycles, she’s probably going to be ovulating, but there are some quite straightforward blood tests that can check for ovulation. The man can do a sperm test, again, via his GP.

Once they get to 12 months of trying if those tests are normal, then usually the third test would be a check of the woman’s fallopian tubes. It can be quite a straightforward test and often that would need to be arranged in hospital. If we see then that the woman’s ovulating, the man’s got normal sperm and the woman’s tubes are open, then very often the suggestion would be to continue trying for a bit longer.

Georgia - Very briefly, is this drop in fertility, are we seeing it mainly in that people just are unable to conceive or is it problems later on that are popping up?

Tim - It tends to be that couples have perhaps a delay in conception, so it’s not common we would see a couple where there’s no chance of conceiving. Very often we would be able to say that their monthly chance of conception may be much less than they would like. But often the suggestion would be to continue trying, perhaps optimise lifestyle and, if necessary, move on to some treatment such as IVF or some drugs to get the woman ovulating.


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