If this happens, you might not realize that you're pregnant — which can lead to mistakes when determining a baby's due date. Implantation bleeding is light, stops on its own and doesn't require treatment. If you're concerned about any vaginal bleeding or vaginal bleeding during pregnancy, contact your health care provider. There is a problem with information submitted for this request.
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The process of implantation can be thought of as a proinflammatory reaction,[ 32 ] given that embryo attachment and invasion into the endometrium require connection to the maternal vascular system. It has long been speculated that prostaglandins PGs , as vasoactive factors, play an important role in ovulation, fertilization, and in late-pregnancy processes leading to the onset of labor. The lack of either of these enzymes leads to an absence of PG synthesis, which then results in several implantation defects.
PGs were shown to be essential for embryo implantation. Their role consists in timing the window of implantation. Delayed timing of blastocyst implantation has a ripple effect that presents in mice as embryo crowding near the cervix, abnormal placentation, and fetal resorption. PGs supplementation can partially restore a normal phenotype. Whether PGs have a similar role in human implantation should be further explored. Their counterparts, the proteoglycans, are found around the trophoblast cells of the blastocyst.
This ligand-receptor system also is present just at the implantation window. Invasion is an even further establishment of the blastocyst in the endometrium. The protrusions of trophoblast cells that adhere into the endometrium continue to proliferate and penetrate into the endometrium.
These penetrating cells differentiate to become a new type of cells, syncytiotrophoblast. The prefix syn- refers to that the boundaries between these cells disappears, forming a single mass of a multitude of cell nuclei a syncytium.
The rest of the trophoblasts, surrounding the inner cell mass, are hereafter called cytotrophoblasts. Invasion continues with the syncytiotrophoblasts reaching the basal membrane beneath the decidual cells, penetrating it, and further invading into the uterine stroma. Finally, the whole embryo is embedded in the endometrium. Eventually, the syncytiotrophoblasts come into contact with maternal blood and form chorionic villi.
This is the initiation of forming the placenta. Embryo implantation is the result of a well-orchestrated sequence of events including cellular adhesion, invasion, and immune regulatory mechanisms, some of which are controlled through genetic processes by the ovarian hormones. It is proposed that an embryo implantation is a well-defined and precise process, in which various factors come into play one after the other, yet remaining in close collaboration.
Source of Support: Nil. Conflict of Interest: None declared. National Center for Biotechnology Information , U. J Hum Reprod Sci. Alok Sharma and Pratap Kumar 1.
Author information Article notes Copyright and License information Disclaimer. Address for correspondence: Dr. E-mail: ude. This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3. See J Hum Reprod Sci.
This article has been cited by other articles in PMC. Abstract Embryo implantation is a well-defined and precise process, in which various factors come into play one after the other. Adaptation of uterus To enable implantation, the uterus goes through changes in order to be able to receive the embryo.
Predecidualization The endometrium increases thickness, becomes more vascularized and its glands grow to be tortuous and boosted in their secretions. Decidualization Decidualization succeeds predecidualiza-tion if pregnancy occurs. Decidua throughout pregnancy After implantation, the decidua remains at least through the first trimester. Pinopodes Uterodomes Pinopods are bleb-like protrusions found on the apical surface of the endometrial epithelium.
Nourishment The embryoblast spends approximately 72 hours in the uterine cavity before implanting. Growth and implantation In addition to nourishment, the endometrium secretes several steroid-dependent proteins, important for growth and implantation. Mechanism Implantation is initiated when the blastocyst comes into contact with the uterine wall. Zona hatching To be able to perform implantation, the blastocyst first needs to get rid of its zona pellucida.
Adhesion Adhesion is a much stronger attachment to the endometrium than the loose apposition. Cellular adhesion molecules family The cellular adhesion molecule CAM family is composed of 4 members known as integrins, cadherins, selectins, and immunoglobulins.
Integrins Integrins are a family of transmembrane glycoproteins. Selectins Selectins are glycoproteins, which also belong to the CAM family. Cadherins Cadherins constitute a group of glycoproteins responsible for the calcium-dependent cell-to-cell adhesion mechanism. Immunoglobulins Among the CAMs family, the immunoglobulins superfamily is the most extensive. Mucins Mucins are high molecular weight MW glycoproteins.
Cytokines T H 1, T H 2, T regs Cytokines comprise a group of proteins that separately or in concert modulate a variety of cellular functions, such as cellular proliferation and differentiation.
Colony stimulating factor-1 Colony stimulating factor-1 CSF-1 expression and receptors for CSF-1 are found both in human endometrium peaking in decidua and in the pre-implantation embryo. Prostaglandins The process of implantation can be thought of as a proinflammatory reaction,[ 32 ] given that embryo attachment and invasion into the endometrium require connection to the maternal vascular system. Proteoglycan receptors another ligand-receptor system involved in adhesion is proteoglycan receptors, found on the surface of the decidua of the uterus.
There has been little research about implantation cramping, but it may affect the lower abdomen or back and feel like:. Early pregnancy can cause additional symptoms, which may start a short time after implantation and continue for the first trimester and sometimes beyond. They can include:. A timeline of implantation and early pregnancy includes the following events, based on a day menstrual cycle:.
The following symptoms can indicate implantation, but they can also have very different causes, including pregnancy loss. It can be a sign of implantation, but it can instead point to:.
Also, bleeding sometimes happens due to a pelvic examination, sex, or a Pap smear. Cramping or lower back pain can indicate implantation, but it can also occur with early pregnancy loss. Because pregnancy tests are now so sensitive, some people know when they have experienced a very early pregnancy loss, known as a chemical pregnancy. The loss occurs at just around 5 weeks. Also, a person might confuse implantation bleeding and cramping with a period, though any symptoms of implantation usually take place a week or so before a period is due.
However, anyone experiencing bleeding or more serious pain should consult a doctor. These may be, for example, symptoms of an ectopic pregnancy , which is a medical emergency. In addition, pregnant people with rhesus-negative blood may need an injection of rhesus immune globulin after any bleeding, to prevent the fetus from developing health issues such as hemolytic anemia, according to the National Heart, Lung, and Blood Institute. Home pregnancy tests detect the hormone human chorionic gonadotropin hCG in urine.
The pregnant body starts producing this hormone before implantation. Levels in the blood and urine double about every 24 hours for 8 weeks, peaking at about 10 weeks.
Therefore, some women may not suspect pregnancy until they miss a period. And if you're still not sure if these are symptoms of your regular menstrual cycle or of early pregnancy, take a pregnancy test to verify any suspicions. Just make sure to follow the directions for the test, and take the test at the right time , or you may get an inaccurate result.
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