The fertilization of the egg with the sperm is considered by many as the beginning of a pregnancy. In reality, even though an egg is fertilized, it may float freely in the womb. The fertilized egg, at this stage, is a cluster of multiplying cells. The attachment of such an embryo, to the lining of the uterus, is referred to as Pregnancy Implantation.
This is one of the earliest stages of pregnancy. At this stage, the embryo is referred to as a blastocyst and it embeds itself in the endometrial lining. Pregnancy is said to have officially taken place at this stage. The foetus receives oxygen and nutrients through this adhesion.
How does Pregnancy Implantation happen?
After fertilization, the egg starts dividing into multiple cells and keeps dividing till it reaches the uterus from the fallopian tube. The endometrium of the uterus prepares itself to provide a window period, to receive the embryo, which occurs between 7 to 9 days after ovulation. This is characterised by changes in the endometrium cells which help to bring the blastocyst near it. These changes include an increase in thickness of the endometrium and production of rounded cells. In case no pregnancy occurs, this layer is shed off in menstruation.
As a part of its preparation, the endometrium develops protrusions which endocytose or fold inwards, to ingest uterine fluid and macromolecules in it. This decreases the volume of the uterus and thus takes the walls closer to the floating embryo blast. This is accompanied by higher levels of progesterone which makes the lining of the uterus sticky, thereby preventing the blastocyst from slipping off the lining. The endometrium also secretes steroid dependent proteins and cholesterol which are important for growth.
Signs of Implantation
A positive pregnancy test may be the first sign of an implantation. Some women may experience light spotting or minor bleeding, brown or light in colour, usually for just a day, just after the embryo implants in the uterine wall of the womb. This spotting occurs at the point where the ovum attaches itself to the uterine wall. This may be accompanied by a slight change in the body temperature of the mother.
The embryo hatches after attaching itself to the lining and secretes chemicals which digest the lining and enable to embryo to move deeper into the lining. A hormone called HCG (Human Chorionic Gonadotropin), which is formed by the cells which eventually become the placenta, can be found in the blood within the first week of implantation. This hormone can be detected by conducting a urine or blood test.
When does it happen?
Implantation may occur anytime between the 6th and 12th day after the egg is fertilized.
The fertilized egg has a 50 percent probability of attaching itself to the uterus. In some cases the implantation may not be complete. Implantation may be hindered by a slippery womb, irritable uterus, uterine fibroids and other such reasons.
The spotting may be followed by a heavier flow of blood, which is dark red in color, signifying a miscarriage. Damaged or incompatible embryos do not survive the two week period.
Precautions To Be Taken During Implantation
The time of implantation is not known and hence nothing specific can be done to ensure success of the implantation. However, if you intend becoming pregnant, you must follow a few general precautions. These include having a healthy diet and drinking lots of water to flush out toxins from the body.
You must also reduce alcohol consumption and quit smoking as these affect chances of implantation. If you have had an IVF cycle, you should remember to take sufficient rest and not over exert yourself after the transfer of the embryo. Also remember to take progesterone supplements as instructed by your doctor. Do not take any medications without taking the advice of your doctor, as these may also hamper implantation.