Often, women have trouble working out their exact due date in the beginning of their pregnancy. The reason being that to work this out without a scan, you need to know when the first day of your last menstrual cycle was – and the last ‘period’ some women think they had, was in fact implantation bleeding.
Implantation bleeding is one of the first signs that you are pregnant. It usually occurs six to 12 days after ovulation and fertilisation. Implantation occurs when the fertilised egg attaches to the uterine lining. This happens when the fertilised egg (now called a blastocyst) has finished moving down the fallopian tubes and adheres to the lining of the uterus. The lining of the uterus is rich in blood and nutrients. When the fertilised egg enters the uterus, the egg “sticks” to this lining, which is called the endometrial lining. Because of the excess blood in the endometrial lining, when implantation takes place some of this blood is disturbed and can drop down into the cervix and exit the vagina.
The similarities between implantation bleeding and your menstrual cycle, is that when implantation occurs, you may feel cramps similar to the ones you feel when menstruating and there is sometimes blood.
However the difference is that the blood will only be slight spottings of a pinkish brown colour as opposed to the five to six day bleeding (on average) of a period. The reason the colour of the blood is different, is that it takes a few days for the blood to travel down after implantation, and it is therefore old and dried. The implantation bleeding normally happens around a week before your period is due, which is why many women confuse it with having a lighter than usual period. The closer the spotting is to your expected period, the less likely it is implantation bleeding.
Once implantation occurs, a blood pregnancy test will be positive in around three to four days, while a urine test will only show positive four to five days after implantation.
However, it is important to note that while all women who fall pregnant will have an implantation, not all women will experience the symptoms of the implantation. In fact only 20 to 30 percent of pregnant women will have spotting and cramps from implantation.
This is the one time in pregnancy (six to 12 days after ovulation) that blood spotting is not something to check with your doctor – rather it’s a sign that in a few days you should take a pregnancy test to confirm that egg is now embryo.