We put this to Oriane from Cambridge Temperature Concepts:

Oriane -   No.  I’ve never heard of that for a woman, unfortunately but sorry.

Chris: -   It would be quite good if they would though. There’d be all these people putting their women in the freezer or in the oven according to what they wanted, wouldn’t they?

Shamus: -   That wouldn't be good.

We put this to Shamus Husheer from Cambridge Temperature Concepts

Shamus -   That’s exactly the same technique that my parents used to have me.  It was very common on the 70s and 80s.  But unfortunately, it’s not highly prescribed to everyone.  The DuoFertility monitor, which we’ve created, ensures primarily that you have no missed measurements which can cause the data to be uninterpretable.  And it’s much more reliable because it measures up to 20,000 temperatures per night and your movement to get the sleeping temperature because when you wake up, the body changes in temperature very rapidly.

So if you change the time that you measure, you can introduce a lot of noise on that data. That means if you’re one of these women with a 0.3-degree temperature change on your cycle, you can completely lose that.  If you’re lucky enough to have a one and a half degree change in your cycle, you’re probably going to be okay.  So it comes down to the accuracy measurement in the noise and also the statistical analysis of that data, rather than waiting for three days after ovulation to determine that you have seen the rise using the old method. We can spot that within a day, which means the egg is still alive, and you still have time to conceive that cycle.

Chris - Well the answer is about 5 mm per minute, and it’s in fact, five body lengths of the sperm per second.  So if you scaled them up, if those were the size of a salmon, that would be the equivalent of the salmon swimming along at 500 miles an hour, or a whale doing 15,000 miles an hour. So the sperm are pretty snappy. They get to the egg pretty fast, certainly within a day or so.

How do they find it? They recognize it by two means. One is a thermal gradient.  They follow temperature so they know that the body gets warmer the further in they go. So they follow the thermal gradient.  And then the second is that the egg oozes out various attractive molecules, in the same way that various inflammatory things attract the immune system in. This pulls the sperm towards the egg because they follow their noses, quite literally. 

We put this to Oriane from Cambridge Temperature Concepts:

Oriane: -   Well, there’s not much information about identical twins being something you can pass on generation from generation.  However, if your mum has a non-identical twin, then your chances of having twins are quite increased as well.

Chris: -   Why is that?

Oriane -   Why is that?  The first one is identical twins which results from one sperm meeting the egg and then the egg dividing into two embryos instead of just one as would occur normally. In the case of non-identical twins, you’ll have the two eggs that are produced and each meets a separate sperm, and that is something that can be passed on generation to generation.

Chris -   Yes.  It’s a very good question because obviously the testes make sperm. They make sperm at about 5000 sperm a second at peak. So they can make sperm at prodigiously fast rates. And they put that sperm into what are called the seminal vesicles, which are structures up inside the body. So sperm are made at a lower temperature, the testicles. That’s why they’re outside the body because the temperature is about one degree lower. But then the sperm are best stored and kept viable inside the body of body temperature 37 degrees.  So they’re going to these seminal vesicles.  They’re nourished there.  They have various components of semen which has got fructose and other sugars and things, and it’s to keep the sperm healthy.

They can survive for quite a long period of time inside the body but eventually they will fatigue and they will age. And of course all the things that you take into your body, cigarette smoke, other toxins and things will damage the sperm potentially.  So they have a sort of recycle time. So sperm that have reached their sell-by-dates get scavenged back and broken down in the same way that, let’s say, blood cells get broken down. And basically any of the nutrients and goodies in the sperm just get recycled back inside the body, and new sperm are produced to make up for the shortage.

Helen: -   So it’s a kind of continual, sort of, replacement, really. 

Chris: -   Exactly.  Those that don’t leave the body eventually break down, and are scavenged back.

Chris -   I think that you could probably make a case.  What do you think, Oriane?  I think you can probably make a case that you could detect pregnancy on the basis of smell because, say mosquitoes, they could be aligned for women who are pregnant.  That could be for a number of reasons.  One of them is that women who are pregnant have a higher metabolic rate so they breathe more.

Oriane: -   They also have a higher temperature.

Chris: -   Yeah.

Oriane: -   Due to the high progesterone during pregnancy.

Chris: -   So it could be either of those things.

Oriane -   Yeah.

Chris: -   But if they’re having a higher temperature, they’re probable exuding more volatile chemicals so they probably where have a slight different smell signature.  The mosquitoes can definitely home in on them.  So I think probably you could train a dog in the same way that dogs can be trained to discriminate urine from people who have renal and bloody cancers, on the basis of the volatile chemicals that the cancer puts into the urine.  Dogs can pick that up.  I reckon you probably could train a dog, something with a very sensitive nose, on, say, a woman’s urine, or on a woman’s sweat in order to tell whether she’s pregnant on the basis of a slight shift in the metabolism of that pregnant person.

Helen -   An interesting form of sniffer dogs, definitely.

Chris: -   Okay. So these are methods of sterilisation. Tubal ligation means that you go inside the peritoneal cavity in the woman, in the pelvis. You identify the fallopian tube on each side. You can see that quite easily because they’re about 5 mm across, and you clamp them. You put a very large paper clip which is squashed onto the tube, and it crunches the tube closed.  And the idea of that is that then what it does is basically squashes the tubes so that the egg released by the ovary cannot make its way down the tube to get into the uterus. And at the same time, a sperm cannot get along the tube to meet the egg and fertilize it. Otherwise, you might get the risk of what’s called an ectopic pregnancy, the actual egg starting to be fertilized and grow outside the uterus.

The risks of tubal ligation are that it doesn’t work. It’s a small risk but there’s nonetheless a risk that you could fail to completely close off the pathway. Another possibility with any invasive procedure is, of course, that you can cause pain.  You could cause bleeding. You could get a localized infection.

With vasectomy, it's a very safe procedure, pretty similar though. You basically are cutting, folding back on themselves and tying off the vas deferens, which are the tubes that carry sperm from the testicle up inside the body. The idea being that then you interrupt the route that the sperm will follow after the testes. The risks are pretty similar to having tubal ligation and the fact is that occasionally there is incomplete severance.  There may be a route by which sperm can still make it through. Also, you don’t stop being fertile. The minute you have it done there’s a flush out or a washout period afterwards.

And so if someone just has a vasectomy and then assumes they’re now no longer capable of fathering children, they could be in for a shock.

Helen: -   And presumably the same question that we had before comes up here that sperm - oh and the testicles that, if it’s not got any way of getting out, it just stays there: but also is broken down over time if it’s not actually released.

Chris: -   Yeah, you don’t end up with your testicles expanding pervasively.

Helen: -   I did always wonder about that, actually.

Chris: -   With all the trapped sperm that’s, sort of, left stuck there.  Unfortunately, no it doesn’t happen.  Thankfully, I suppose.  (Laughing)  In fact, it’s just basically broken down and those cellular constituents get recycled.