The lower part of the uterus that extends into the vagina and serves as a reservoir for sperm after intercourse. Functions of the Cervix: Protective Barrier: Acts as a gatekeeper between the vagina and the uterus, preventing infections. Pregnancy Support: During pregnancy, the cervix remains closed and firm, preventing preterm birth. Before labor, it softens and dilates to allow childbirth. Sperm Reservoir: After ejaculation, sperm can collect near the cervix before continuing their journey toward the fallopian tubes for fertilization. Cervical structure and function play a crucial role in fertility and pregnancy, and any disruptions (e.g., cervical weakness, blockages, or chronic infections) can impact conception and pregnancy maintenance.
A condition where a pregnancy test is positive, but hCG levels are too low for an ultrasound to confirm pregnancy. This contrasts with a clinical pregnancy, where a gestational sac is visible in the uterus. Characteristics of a Chemical Pregnancy: Occurs in the very early stages, typically before week five. hCG levels rise slightly, then start to decline, preventing further pregnancy development. Many women are unaware they were pregnant since it often ends with a slightly delayed menstrual period. Possible Causes: Chromosomal abnormalities in the embryo Improper embryo implantation Hormonal deficiencies (e.g., low progesterone levels needed to sustain pregnancy) Medical Significance: A chemical pregnancy does not necessarily indicate fertility issues, and most women who experience one go on to conceive successfully. However, if it recurs multiple times, medical evaluation may be necessary.
Chimerism is a rare genetic phenomenon that occurs when a woman is pregnant with twins, but one of the embryos fails to develop, and its cells are absorbed into the surviving twin’s body. This type of chimerism is known as "tetragametic chimerism", as the individual is formed from two sets of reproductive cells (gametes)—two eggs and two sperm. However, other types of chimerism can arise under different conditions. Characteristics and Implications: Most people with chimerism are unaware of it, as there are no visible external symptoms. It is rarely diagnosed, since screening tests for chimerism are not routinely performed, and the phenomenon is not well known in the medical community. In some cases, chimeric individuals may fail paternity or maternity (DNA) tests, as different cells in their bodies may have genetically distinct DNA, making their child appear less genetically related—as if they were an uncle/aunt instead of a direct parent. Does chimerism cause health issues? Generally, chimerism does not cause significant medical problems, but it may be unexpectedly discovered during advanced genetic testing.
A process in which a single cell (zygote) divides progressively into multiple smaller cells, first into two cells, then four, then eight, and so on. Importance of Cleavage in Embryonic Development: A critical stage of early embryonic growth, where cells divide but do not increase in size, forming a compact mass called the morula. In in vitro fertilization (IVF), cleavage rate and regularity are monitored in embryology labs to assess embryo quality before implantation. Irregular cleavage (e.g., slow or asymmetric division) may indicate developmental issues, reducing the chances of successful implantation and pregnancy. Early-stage cleavage is a key indicator of healthy embryonic development, influencing the selection of high-quality embryos for IVF transfer.
A pregnancy confirmed by ultrasound, where a fetal heartbeat is detected. Unlike a biochemical pregnancy, which is diagnosed only through hCG hormone levels in the blood, a clinical pregnancy is an advanced stage in which a gestational sac and fetal heartbeat can be clearly observed via ultrasound. Diagnosis: A clinical pregnancy is typically confirmed between weeks 5-7, depending on embryonic development and implantation timing.
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