The Science of Pregnancy

For some getting pregnant is as easy as falling off a log, for others it can be a long and frustrating journey. Everyone is unique in their own little ways adding to the confusion of myths, mysteries and old wives tales about how to get pregnant, stay pregnant and survive childbirth.

I have a seriously scientific brain (with a confusing bundle of emotion on the side – but that’s another story). So when “lie back and think of Britain” didn’t come up with the goods I dusted off the textbooks and took myself back to school… and then did experiments on myself!

Thanks to the wonders of modern medicine I had been able to ignore the vagaries of the menstrual cycle and live life on a pretty even keel… if somewhat significantly dulled. I wrote about my 19 years on the pill and I’m glad those days are behind me.

I found coming off hormone control, and re-establishing a normal hormone cycle, was like riding a roller coaster you can’t get off. I needed to understand more about what was going in my body in order to cope. So I started using tracking apps; Clue to start with and later Fertility Friend.

hormone graph

I rediscovered this old familiar graph from Biology days on Fertility Friend

It’s actually a little more complicated in that there are four main hormones involved. Two from the pituitary gland: Luteinising hormone (LH) and Follicle Stimulating hormone FSH; and two from the ovaries: Estrogen and Progesterone.

The interplay of the four hormones is what drives the release of our eggs and the changes in the womb thickness. For some great videos check out bbc bitesize or s-cool revision sites!

Four hormones cycle
From https://en.wikibooks.org/wiki/GCSE_Science/Hormones
Oestrogen: causes the growth of the womb lining and inhibits FSH. It stimulates release of LH and hence release of the egg until after ovulation when it inhibits LH so that only one egg is released (usually).

Progesterone: maintains the womb lining and inhibits LH after ovulation, if the egg is fertilised this maintains the pregnancy.
LH: Stimulates the release of the egg (ovulation) and stimulates oestrogen and progesterone production in a positive feedback situation.
FSH: Stimulates egg development and the release of oestrogen.

The rise in LH and FSH causes a rise in body temperature which can be measured using a one or two decimal place thermometer. A more accurate thermometer can give a better picture if used at the same time each morning before getting out of bed. This is Basal Body Temperature (BBT) tracking.

You can also test for LH using Ovulation Predictor Kits (OPKs). These work by testing for the presence of the hormone in your urine in just the same way as a pregnancy test. It’s not an exact science as there are false surges, a base level of LH in your system and they don’t guarantee that you actually ovulated. But they can give you an insight into your cycle patterns.

There are other signs to look for including cervical mucus monitoring… This is a highly personal thing to be checking and not as easy to decide on which state you are in. The idea is to look for cervical mucus that is similar to egg white consistency. This is nourishing to sperm and helps them to reach where they need to be. To be honest I knew that this wasn’t for me as its so subjective, also (sorry if tmi) I couldn’t figure out whose fluids were whose with all the bonking going on!

So here is where the Science got real… I decided to do an experiment on myself…

Aim: Get pregnant! OK, and understand more about my body!

Method: Lots of sex!

Testing: Record cycle details, daily OPK testing, daily BBT tracking.

BBT Tracking

I had started tracking my temperatures back in April after I had a miscarriage. They were all over the place and not at all like the sample graphs. I think this was down to remaining progesterone in my system. When I started this cycle on the 18th May I decided to use Fahrenheit rather than Celsius. My one-decimal place thermometer gave more detail in Fahrenheit. It’s a really old digital thermometer that I’ve always used when I’m ill. It makes an annoying beep when it’s done but it’s pretty reliable. I did buy one of these thermometers but I wouldn’t recommend it as it’s all over the place with readings varying more than half a degree in places – not great when you are looking for tiny variations. N.B. I did have to ask @me2mummy where to measure BBT! For clarity, I measured my temperature in my mouth (like you do when you are sick), but you can do it vaginally too… just don’t muddle up the thermometers! Check out her comparison here.

Each morning when I woke up I took my temperature without fail… but I don’t wake up at the same time each day. It varies between 5 am and 9 am depending on what work I have to do. Over the course of this cycle I was in about 10 different sleeping places; some of which were outside. Therefore my environmental variation was huge; from the heat of Crete, to the chill of good old English woodlands. However, even with these challenges you can see an overall pattern. Day 1 to 16 my temperature is 97.5°F or lower, with the lowest at 96.8°F. After Day 16 it is 97.5°F or higher, with a high of 98.3°F. Day 19 and Day 26 are the only two exceptions to this and these two days correspond with me sleeping out on rather chilly nights and not having enough blankets to stay warm. They were particularly bad nights where I also had to get up and go trek across the cold field to the toilet.

Fertility Friends Chart showing progress through cycle to positive pregnancy
Now while I can look back on these drops and count them as anomalies I did have big worries at the time. I know now that this cycle started successfully (hang in there Bean) but at the time these temperatures were a big deal and did cause some anxiety.

You can see that I did record other symptoms into the Fertility Friend app but I can’t find any pattern or correlation, with one exception… Sex Drive. I’m a firm believer in going with the flow so when body said “lets bonk” I didn’t really think twice and luckily Hubby was willing!

OPK Tracking

This was a totally new one for me and one of my first questions was… what’s a positive?


The instructions are somewhat confusing with faint first lines being a negative. The consensus is that both lines have to be equally dark to count as a positive.

One Step Tests
Ok… when to start? This I couldn’t not figure out… if I wanted to use the minimum number of test strips then I should wait until mid-cycle… but what if I missed it?

You can get some basic strip tests online (Amazon) and once I figured out that they were about 12p a test I decided that this was affordable and to go the whole hog and do one every day once I finished my period. I got the combined pack: 30 green for ovulation test, 10 blue for pregnancy test.

I found it easiest to wee in a pot with these tests. They are not protected by a plastic cover and you only dip the very end. I’m totally not accurate enough to wee on a specific spot!

Collection of OPK test strips – somewhat faded but still showing the overall pattern.

My first solid OPK positive came on Day 16 in the morning… not great when Hubby has gone off to work… hmmm. Well that also brings me onto the downside of OPK testing. When you get that result it is almost too late anyway! For best results you need to be having sex two days before ovulation. The egg only lasts 12-24 hours once released (unless fertilised). Sperm can hang around for 5-7 days. Not a nice thought but getting the little swimmers to the right place at the right time is the main challenge. I think we had it covered… we had sex on days 6, 9, 10, 11, 12, 13, 15 & 16… yeah ok, I may have turned into a total nympho over this baby thing. Baby making sex is so good!

Results: PREGNANT!!!!!

Evaluation: While I’ve loved being the subject of my own science investigation I’m not sure whether it’s all worth it. Knowing more about my body and being able to “feel” the cycles and go with them rather than fighting them is definitely a positive. However I feel that outside of the framework of a science investigation I think I would drive myself demented trying to understand all the tiny signs and symptoms. The anomalies in temperatures were actually pretty stressful and that is the last thing that you want when trying to conceive.

Going further…

Once I started investigating I couldn’t stop so I did a few further tests…

Investigate: How does the pregnancy test line progress over time?

Collection of Pregnancy test strips from Cycle Day 28 – 35 plus week 5 &6; green OPK strip at bottom shows reaction to the presence of HCG not LH.
It wasn’t much of a surprise to see that each day the test line gets darker and darker. This was very reassuring to me this time as last time it didn’t get much darker than the fourth strip in this series (day 29). What was really interesting was the speed at which the line appears as time progresses.

Investigate: Do OPK tests show positive for pregnancy?

Yup they do – see image above. I tested on day 35 with a pregnancy test and an OPK test. Both come up with strong positive results. This is because the Human chorionic gonadotropin (HCG) that is being detected in the pregnancy test is very similar to LH. HCG stimulates the Corpus Luteum (the leftover cyst of the released egg) to continue to produce progesterone and maintain the womb lining and protect the implanted embryo until the placenta can form.

Despite the huge emotional upheaval of having a miscarriage I think I might actually be in the falling off a log category! I’ve got the getting pregnant thing sorted… now to hope that I can work out the rest of the staying pregnant bit.

My heart goes out to all of those trying to conceive and looking for the answers in signs, symptoms and tests. I hope that these bring you comfort and support, but if they start to take over the process and induce more stress then I hope you can let them go. Make sure that these things are only helping you and remember to enjoy your relationship and the sex as priority one! Good luck.

Rhyming with Wine
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8 Comments Add yours

  1. Kitty says:

    Interesting stuff. I think stress can really hamper chances of conception and I feel for anyone who struggles to conceive a longed for baby. I am adopted and my mum used to tell me about so many women she knew who would adopt after years of infertility and then conceive naturally very quickly afterwards

    Liked by 1 person

    1. RawMum says:

      Thank you for your thoughts. I’m glad you found your forever home. Adoption and fostering is such an amazing thing to take on. Releasing that burden and enjoying life often brings more rewards than expected.

      Like

  2. I found this so fascinating to read. I also found the same with my positive pregnancy tests and found it reassuring to see the line continue to get darker each time we tested. I dread to think how many we went through as the wait to 12 weeks seems to take forever. I’m all for applying science wherever we can! Thanks for linking to #DreamTeam lovely x

    Liked by 1 person

  3. Surrey mama says:

    So interesting. I wish I had read this before we started trying for the girls! i really hope you have some positive news soon xx

    Liked by 1 person

    1. RawMum says:

      Thank you. How long did you have to try? I’m currently coming up to 9 weeks and very hopeful that this one will stick it out.

      Like

  4. Wow, there’s quite a lot to it isn’t there? I opted for the “have a lot of sex” way of getting pregnant and it worked out pretty well. 😉 Congrats on the pregnancy lovely.
    Thanks for linking to #pocolo

    Liked by 1 person

    1. RawMum says:

      Yeah it’s the fun way too 😜 fingers crossed this one sticks around 🤞🏻

      Like

  5. Congratulations on the pregnancy. This was really interesting to read. I’ve never seen it tracked like this before! #pocolo

    Liked by 1 person

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