Chemical Pregnancy: EVERYTHING you need to know

What is a Chemical Pregnancy?

Whilst going through our first round of IVF we got a false positive on one of our pregnancy tests. It was at that stage where it is likely that the hCG injection was out of my system. This led me to wonder

“Did I get pregnant and lose it early”

“Did I do something wrong, which meant that my little Emby didn’t stick”

“Why didn’t it work for me”

I decided after this to look into Chemical Pregnancy and research it and this is everything that I managed to find.

A chemical pregnancy is a positive pregnancy test due to an increase of hCG excreted by the hatching and implantation of a blastocyst in early pregnancy. Although this pregnancy is never picked up in an ultrasound scan and or further home pregnancy tests come back negative and is thus called a chemical pregnancy.

How common is Chemical pregnancy?

When I experienced my false positive, I felt alone and wondered why this happened to me. As I was looking into this, I felt semi-relieved that I wasn’t alone, and it was in fact sadly particularly common.

Studies have indicated that of all first-time pregnancies, between 50-60% of those ends in some form of miscarriage. With a substantial portion of those people experiencing a chemical pregnancy. Furthermore, it is estimated that 25% of those lose a pregnancy before they get any symptoms or have any thoughts that they could be pregnant.

A study was performed by De Neubourg of 370 top grade blastocyst fresh implants and the following was found 29.7% of resulting pregnancies were lost, with 52.6% being chemical pregnancies.

A further study into FET (Frozen Embryo transfers) by Salumets et al looked at 1,242 FET’s and it showed that 33.3% of all pregnancies were lost and 18.4% of those being chemical pregnancies.

As you can see it appears that chemical pregnancy rates for those going through IVF and FET is around 1 in 5 to 1 in 2 of those who get a positive pregnancy test.

What causes chemical pregnancies?


Throughout my first failed IVF cycle I wanted to understand why certain things happen, in order to understand what possibly causes a chemical pregnancy we need to understand a little about the biology of very early pregnancy.

The biology of early pregnancy

The infographic above gives you a simple overview of what happens in very early pregnancy. Through the implantation the levels of hCG increase as they are released by the embryo and also by the endometrial cells along with a number of other chemicals and enzymes which support implantation. This rise then leads to a positive pregnancy test. Sadly, in a chemical pregnancy test this occurs and then the pregnancy fails.

What causes the failure of the pregnancy?

Firstly, it is important to state that the exact aetiology (cause of disease) is not fully understood however, research into the area is starting and the following is the thinking at this point in time.

What is clear from all these studies is that the genetic makeup and the spindle (a collection of microtubes which form as cells divide) are vital in these early stages of embryo development. A handful of key studies have identified 3 key reasons for early chemical pregnancy.

  • Chromosomal abnormalities within the embryo which mean that they are incompatible with life.
  • A clear link between endometrial thickness on the day of the hCG injection seems to have a very clear link with chemical pregnancies. One study by Dickey et al only looked at 81 cycles but in those found those with an endometrial lining less than 9mm had a 21.9% chemical pregnancy rate as opposed to a 0% for those with greater than 9mm. Now this was a very small study and more needs to be done to confirm.
  • Sperm DNA damage is reported to greatly increase the risk of early pregnancy loss according to the study by Zini et al. It looked at 1549 cycles and the odds ratio (correlation between two events) between sperm DNA damage and early pregnancy loss and chemical pregnancy was 2.48 which shows a very close relationship between the two.

Why are Chemical pregnancies important?

When we had our positive result in our first failed IVF cycle it took both me and Nathan on an emotional rollercoaster, we were hopeful and excited. Even though we’re both fairly logical and understood that it could have been a false positive and that early pregnancies are very vulnerable we still got our hopes up which then meant that the negative hit harder than it may have if we’d not have had that glimmer of hope.

For all of us going through IVF, ICSI and other assisted reproduction techniques, we have been trying to conceive for a long time. This means that any chemical pregnancy is a very disappointing event, it hurts a lot.

One of the key reasons that they’re important is that they can have impacts on your emotional and mental health. They often raise questions such as:

  • Why did this happen?
  • Did I do something to harm the embryo?
  • Does this mean I am never destined to have a baby?
  • Does this mean my uterus is defective and is rejecting the baby?

The most important thing to remember is that


In fact, a chemical pregnancy even though it is devastating is shown as a positive within research literature. One study by Pearson et al looked at 2,245 women who had experienced a chemical pregnancy during an IVF/FET cycle. It showed that of those who continued to try IVF that they had a statistically significant greater chance of pregnancy than those who hadn’t had a chemical pregnancy by 34% to 21%. So, as they say every dark cloud has a silver lining. This is because the positive hCG showed the implantation process did start which means the prognosis for a healthy pregnancy vs someone with no positive hCG is improved for future treatments.

Unfortunately. the same study also showed that women who had experienced a chemical pregnancy were less likely to go on for more IVF treatments when compared to those who had an unsuccessful cycle. This demonstrates the serious emotional impacts that a chemical pregnancy can have upon the couple.

Can a chemical pregnancy be treated?

A chemical pregnancy itself cannot be treated. It is very important to ensure that another hCG test is performed after the negative following the chemical pregnancy to ensure you aren’t pregnant.

However, the emotional and psychological impacts of chemical pregnancies should certainly be tackled in a follow up meeting with your clinic. They should help you understand the evidence presented to you in this article to try and ensure you understand that even though this is an incredibly hard time, it has positive ramifications for future IVF treatment.

What are the signs and symptoms of a chemical pregnancy?

Many women who experiences this don’t actually have any symptoms, however in those that do these are the most common.

  1. A positive pregnancy test (in IVF this has to be after the hCG injection is out of your system – or this would be deemed a false positive) which is then followed by a negative test.
  2. Mild spotting a week before you would expect your normal period (although in IVF this could also be implantation bleeding so it’s not diagnostic in itself)
  3. Mild abdominal cramps
  4. A slightly heavier period than usual, this can sometimes come a little later than expected.
  5. Passing of clots from the vagina

Can I prevent a chemical pregnancy?

It is with the utmost regret that I say you can’t. There is a lot of information out there which talks about eating the right foods, doing certain things. The issues is there is no evidence there to support them preventing chemical pregnancies.

Keeping healthy as advised through the conception journey, eating a balanced diet, taking your prenatal vitamins and finally ensuring you use your progesterone medications to support that early pregnancy are all you can do.

It’s important to realise that even if you do all these things it’s still a very real possibility you could have a chemical pregnancy. These things other than the progesterone support and your folic acid (which are shown to help with all elements of conception and early pregnancy) will help you with your peace of mind thinking you have tried everything.


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