There are many different signs and symptoms of pregnancy and most of them mimic the imminent arrival of your period. Bleeding, strangely enough, can also be a sign that you are pregnant, and we refer to this as ‘implantation bleeding’. Although implantation bleeding is not that common it is something that many women have concerns about. Implantation bleeding can also confuse the dates your midwife may give you for your estimate birth date, based on the first day of your last menstrual period.
When you do see your midwife they will ask you when your last menstrual period was and also if it was ‘lighter’ than normal. From this they can deduce whether or not this was an implantation bleed and ‘date’ your pregnancy as 4 weeks earlier. This is important when it comes to timing your 12 week or ‘dating’ scan; too late and you may miss the window for some of the screening tests that are offered.
What is implantation?
Once your egg has been fertilised it then has to travel through your fallopian tube, into your womb and burrow into the lining of your womb, or ‘implant’. This stage usually takes around seven days from fertilisation. The rule of thumb is that ovulation occurs around two weeks after the first day of your last period, and fertilisation around 24-36 hours after ovulation.
To confuse things a little more, sperm can survive for up to seven days, so the day that you had intercourse may not be the date you conceived. Sperm can easily wait up to a week in your fallopian tube for the egg, which in contrast will usually only live for 24-36 hours. Your conception date is all to do with when your body released your egg.
As with everything in nature, our bodies never seem to follow the textbook and some of us may well release our eggs days before or after day 14. Without knowing when the egg was released it is difficult to date pregnancies accurately and it’s for this reason that we use your period and their normal length and cycle as the reference for how far along in pregnancy you are.
The graph below shows the passage of time for pregnancy in someone with a 28 day menstrual cycle.
Day 1: 1st day of your period
Day 7 – 15: Intercourse
Day 14: Ovulation
Day 14-15: Fertilisation
Day 21: Implantation (with possible bleeding)
Day 28: Period due positive pregnancy test and 4 weeks pregnant
What's the difference between implantation bleeding and a normal period?
You would usually have expected your period a few days to a week after any implantation bleeding. It’s extremely easy to mistake the implantation bleeding for an ‘early period’ as many of the pre-menstrual symptoms, such as cramps, bloating and mood changes are present with pregnancy too. The difference with a period and an implantation bleed is the length of the bleeding, the colour of the blood loss and the heaviness of the blood flow. A period would normally last 4-7 days and be heavier, with a consistent flow of blood and darken to red. Implantation bleeding usually begins as brown or pink and remains extremely light.
How long does implantation bleeding last?
Implantation bleeding usually lasts around 1 -2 days, but can last anything from a few hours to spotting on and off for many days, and be extremely light, and stay light. As with everything, everyone is different, and a few women may feel that the implantation bleeding lasts as long as their period.
What does implantation bleeding look like?
The blood is usually brown or pink and is usually contained in a panty liner, rather than a sanitary pad. It is different from the darker red blood associated with a period, however many women begin their period with this type of blood loss and if they’re not expecting to be pregnant may mistake it for a period. Most women with implantation bleeding will feel that their period was early, very light and use words such as ‘spotting’. This ‘spotting’ may continue for 2-4 days in some women, and for those not expecting to be pregnant may simply mistake this for a ‘light’ period and think nothing else of it, until they miss their next period
Is implantation bleeding a sign of misscarriage?
Implantation bleeding is not a sign that there is anything wrong with the pregnancy and there are no links to implantation bleeding and miscarriage. If you do think that you may have had a lighter than normal menstrual period it’s probably a good idea to take a pregnancy test one week later. Not only will this confirm your pregnancy, it also lessens the chances of your midwife incorrectly calculating the date for your first scan and therefore limiting your access to certain screening tests that can be done.