Implantation bleeding is considered to be an early sign of pregnancy and it occurs around the time of the following menstruation cycle. Mood swings, cramping, headaches, and brown or pinkish spotting or discharge are common signs that accompany implantation bleeding. Generally, one-third of women may encounter implantation bleeding during their pregnancy process.
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When the women become pregnant, the fertilized egg that is attached to the uterus lining will begin to grow resulting in implantation bleeding. Implantation bleeding is a normal process and may not need medical attention.
During the ovulation process in women, the ovum is released from the ovary. This ovum is picked up by the fallopian tube. The ovum stays in the fallopian tube for about 12–24 hours. During this time, the ovum is fully functional and stays alive. When sperm is deposited in the vagina, it swims into the uterus through the opening of the cervix and moves further into the fallopian tubes.
Of the many sperms that may travel, only one will fuse with the ovum. The sperm penetrates the cell membrane and deposits the male genetic material into the ovum and the two nuclei undergo fusion. The ovum is fertilized in the fallopian tube; now termed as the fertilized ovum or zygote, it stays for around 72 hours in the fallopian tube.
During this 72-hour period, the zygote develops rapidly. Initially, it divides into two cells. Then the divided cells again subdivide into four cells. This cell division process happens many times and at the end of the 72-hour period, the cells resemble a solid ball called morula. Now, the cells in the morula divide further, which makes the cells to move toward the outer edge of morula, making the morula resemble a hollow ball. After fertilization, this hollow ball-like structure of the cell (now termed as blastocyst) is formed in about 5 days.
The blastocyst may take about 5–7 days to reach the uterus. Upon reaching the uterus, the blastocyst gets attached to the lining of the uterus which is termed as implantation. This stage is termed as the beginning stage of pregnancy, provided the embryo survives in the uterus.
During this cell movement process, some blood vessels present in the wall of the uterus may break and cause bleeding. Followed by ovulation, it may take about 10 days to 2 weeks for the complete movement and bleeding to occur.
Upon successful implantation of the blastocysts, the cells will multiply further aiding in the growth of the fetal membranes and the placenta.
When the embryo cannot get implanted, the survival period is just a few days, after which it gets detached from the uterus and moves out of the vagina along with menstrual fluid.
Occasionally, the blastocysts get attached to the fallopian tube and implantation may happen in the tube. As the embryo grows, it may rupture the fallopian tube and may result in severe pain and blood loss for the woman.
Implantation bleed versus menstruation bleed
After ovulation, menstruation will happen after 14 days. So there is confusion about the bleeding—whether it is due to menstruation or implantation and some women may think that they are late for their periods. Somewhere around the 22nd or 25th day, light pink color spots may be seen, a few days prior to the regular menstruation signal. When the egg moves, light bleeding may happen. The bleeding may resemble menstruation bleeding; however, there are differences between the two.
Blood color: Blood flow during the menstruation period varies in women. Some women may have heavy blood flow while some others may have a lesser flow. In any case, the color of the spotting is the same across all women as the bleeding location is the same every time. On the other hand, in implantation, the blood is dark brown (rust color) or more pinkish, and the blood seems to appear aged.
Blood consistency: During menstruation, some women may have thick blood clots during blood flow. In case of implantation bleeding, the consistency of the rust color or pink color blood will be the same throughout.
Bleeding flow pattern: Implantation bleeding starts with light spotting and heavy flow may follow after a few days of light spotting. Whether the women are lightweight or overweight, the implantation bleeding pattern is the same.
Bleed duration: In the case of menstruation, most women have their period lasting between 2 and 7 days. Implantation bleeding may last for a few hours or even up to 2 days. Bleeding may be more in women experiencing their first pregnancy compared with women who have had egg attachment earlier.
When the bleeding is less, it is not a matter of concern during the initial stages of pregnancy as there is no risk involved in the development of the baby; bleeding could also be due to vaginal infections, cervix irritations, or sexual intercourse. Extended bleeding is a sign of concern, particularly during pregnancy.
Reviewed by Susha Cheriyedath, MSc