What is the magic moment when a pregnancy truly begins? How do we know that a new life is about to develop and grow? Many of us assume it is the moment when a female egg is met by a male sperm and fertilisation takes place. But this is not quite accurate, nor is it the full picture of the start of a pregnancy. One way of looking at the true start of pregnancy is to see it as the point of implantation. Implantation bleeding is often, but not always, a sign that this has happened.

Here we take a look at the journey that the fertilised egg needs to complete before it reaches this critical point and why it sometimes leads to bleeding. We also answer your questions, such as how you can recognise it, how long the implantation bleeding last and what you should do in the event of heavy implantation bleeding.

What is implantation bleeding?

Implantation bleeding only happens in about one third of pregnancies, so if you are pregnant but have not had any sign of implantation, it’s nothing to worry about! When implantation bleeding does occur, it is light vaginal bleeding or spotting that can take place between seven and 14 days after the egg and sperm have met inside the fallopian tube and the egg has been fertilised. Between these two events, the fertilised egg, which is not yet an embryo, has some developing to do and a journey to make.

The journey from fallopian tube to uterus

From the moment it is successfully fertilised, the egg prepares to divide and grow. It remains a single cell for a period of about 12 hours before starting to divide. After about 30 hours, it has divided from a single cell into four cells and after another 24 hours, this multiplies to eight. The process continues and the fourth day after fertilization, the embryo becomes a tiny berry-like structure of 16 cells called morula. In the meantime, the lining of the womb, the endometrium, which has already thickened as part of the menstrual cycle, starts to change and thicken even further in order to be able to support a growing embryo over the nine months of pregnancy.

The cells continue to differentiate and five or six days after fertilisation, they have become a blastocyst made up of hundreds of cells. This makes its way slowly down the fallopian tube, carried by cilia, small hair-like projections inside the fallopian tube, to finally arrive inside the uterus. Here, if a successful pregnancy is to follow, it will implant itself into the endometrium as the conduit for nourishment from the mother’s blood supply.

Implantation bleeding

This is the time when implantation bleeding may be noticed. As the blastocyst embeds itself into the lining of the uterus, it sometimes causes the rupture of tiny blood vessels at the site of implantation. This does not cause any long-term damage or injury as the endometrium is well able to repair itself, but It can cause the light bleeding that we know as implantation bleeding.

Can you have implantation bleeding with IVF?

During the IVF procedure, the selected embryo is placed directly into the maternal uterus with the help of a cannula. Even though it does not have the same journey to make on its way to the uterus, the embryo still needs time to go through the development process before it is ready to implant. When a woman becomes pregnant with the help of IVF, the likelihood of implantation bleeding therefore remains the same.

How can you tell implantation bleeding from a period?

Telling the difference between a period and implantation bleeding is made more difficult by the fact that implantation bleeding usually occurs within a couple of days of when your next period would be due. This makes it easy to mistake for normal spotting leading up to a period. Some women report that the blood is darker than the bright red colour of a normal period. For others, it can be accompanied by mild cramps. Again, if cramping is something you experience along with a normal period, it can be difficult to distinguish between the two. You can only know retrospectively whether the shorter duration indicates that it was not a period.

How long does implantation bleeding last?

Implantation bleeding is usually both light and brief in duration, lasting no more than one to two days. It could be a matter of a few spots from time to time or a light constant flow. In some cases, a woman may only have a few hours of spotting and nothing else.

Whether or not you are hoping that your light bleed is a sign of pregnancy, you can’t be 100% sure without taking a pregnancy test. It’s best to wait until about a week after your normal period would have been due before using an over-the-counter pregnancy test. You may also be watching out for other signs of early pregnancy. These can include cramping, nausea, frequent urination and breast tenderness. Some women also experience constipation, bloating and unusual food aversions. If you need to know more, take a look at our article about the early signs of pregnancy.

When should you talk to your doctor?

Heavy implantation bleeding is very rare, and it does not have clots in the same way that normal period bleeding sometimes does. If you have any heavy bleeding that you think is not a normal period, you should seek medical advice immediately. If you suspect you may be pregnant, heavy bleeding could indicate a problem or even the beginning of an early miscarriage. However, if you have light bleeding that you think may be a sign of implantation, you should take a pregnancy test. If it turns out you are pregnant, of course you need to make an appointment with your doctor so that the standard antenatal care programme can be put into place.

Don’t forget that not every pregnant woman has implantation bleeding. You can be pregnant without any bleeding or you could have some spotting without being pregnant. A slight bleed is not necessarily a sign of something being wrong, so don’t worry, just take a pregnancy test to make sure. If it turns out you are pregnant, congratulations! If not, and you feel you are having fertility problems, do browse our website to familiarise yourself with the options for treatment available, or get in touch directly through our online contact form.