A
Amniocentesis - an invasive prenatal test in which amniotic fluid (in which the baby floats) is extracted by means of a hollow needle inside the uterus. Read more about prenatal invasive testing here.
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Source: Roca P. Amniocentesis. In: Ramus RM, Talavera F (eds.). Medscape. 2018. Available from: https://emedicine.medscape.com/article/1997955-overview [Accessed September 3rd, 2022]
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Aneuploidy - abnormal number of chromosomes in a cell. This could be more (e.g. trisomies = 3 chromosomes) or fewer (e.g. monosomy = 1 chromosome only) than the usual two chromosomes, in one or more specific pairs.
Source: O’Connor C. Chromosmal Abnormalities: Aneuploidies. Nature Education. 2008;1(1):172.
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Autosomal chromosomes - all chromosomes which are not sex chromosomes. This means chromosome pairs 1 up to and including 22.
Source: Alberts B, Johnson A, Lewis J et al. Molecular Biology of the Cell. 6th ed. New York: Garland Science; 2015.
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B
Blastocyst stage – an early development stage of an embryo. It forms an outer cell mass, which will give rise to the placenta, and an inner cell mass, from which the embryo itself will develop.
Source: Gilbert SF. Developmental Biology. 6th ed. Sunderland, USA: Sinauer Associates; 2000.
C
Cell division - during the process of cell division, the chromosomes inside the cell are duplicated so that each daughter cell obtains a complete set of chromosomes after the whole process. With high maternal age, there is an increased amount of cell division errors, causing the chromosomes to be not properly divided among the two daughter cells. This can result in monosomy and trisomy.
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Source: Alberts B, Johnson A, Lewis J et al. Molecular Biology of the Cell. 6th ed. New York: Garland Science; 2015.
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Cell free (fetal) DNA – degraded DNA fragments shed into the bloodstream. Cell-free DNA (cfDNA) refers to different types of circulating DNA building blocks that are freely moving in the circulation, such as circulating tumor DNA, cell-free mitochondrial DNA (which is DNA from the energy-producing part of a cell) and cell-free fetal DNA (cffDNA) from the placenta during pregnancy.
Source: Gravina S, Sedivy JM, Vijg J. The dark side of circulating nucleic acids. Aging Cell. 2016 Jun;15(3):398-9. DOI: 10.1111/acel.12454.
Cervix - the lower, narrow part of the uterus (womb), connecting the uterus and the vagina. The cervix is also called the birth channel, because the baby exits the womb through this part.
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Source: Paulsen F, Waschke J (eds.). Internal Organs. 16th ed. Munich, Germany: Elsevier; 2018.
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Chorionic villus sampling - an invasive prenatal test in which bits of tissue called villi are removed from the placenta, after which the sample is tested for abnormalities. Read more about invasive prenatal testing here.
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Source: Jones TM, Montero FJ. Chorionic Villus Sampling. In: StatPearls. Treasure Island, USA: StatPearls Publishing; 2018.
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Chromatid - during the process of cell division, your chromosomes are duplicated so that they can be distributed equally over two new cells that contain the exact same genetic information. Until then, the duplicated chromosomes stay attached to the original ones. Both the original chromosome and the duplicated chromosome in a pair are referred to as a chromatid while they are attached.
Source: Wadsworth P, Titus J. Mitosis. In: Lennarz WJ, Lane MD (eds). Encyclopedia of Biological Chemistry. 2nd ed. Philadelphia, USA: Elsevier; 2013. p. 181-184.
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Chromosomal abnormalities - any structural or numerical abnormality of one or more chromosomes. This can involve aneuploidy, breakage of the chromosome, chromosomes having lost or exchanged big chunks, polyploidy (in which case a cell contains more than two copies of all chromosomes, for example four or eight copies of every chromosome) and more. These issues can happen in any chromosome, including the sex chromosomes. A person might be born with a chromosomal abnormality, which is referred to as a congenital abnormality. In this case, most of that person’s cells are typically affected. In other cases, a person develops the abnormality at some point in life. This is referred to as an acquired abnormality. In this case, only a small portion of a person’s cells are affected. What the effect of any given abnormality is, depends on which cells are affected, how many of them are affected, and in what way. This varies greatly between cases.
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Source: Queremel Milani DA, Tadi P. Genetics, Chromosome Abnormalities. In: StatPearls. Treasure Island, USA: StatPearls Publishing; 2022.
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Chromosome - your entire genetic code is subdivided into several separate DNA molecules, each of which forms one chromosome by becoming very tightly wound and by associating with proteins that help form this dense shape. This saves a lot of space compared to if your DNA was floating in your cells stretched out (in which case it is about two meters or six feet) – and it makes organization within the cell nucleus (where the DNA is) much easier. Each of your cells contains 46 chromosomes arranged in pairs – you inherited one of the pair from your father and one from your mother. Most of your chromosomes (22 pairs) are autosomal chromosomes; the last pair are your sex chromosomes.
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Source: Alberts B, Johnson A, Lewis J et al. Molecular Biology of the Cell. 4th ed. New York: Garland Science; 2002. and Queremel Milani DA, Tadi P. Genetics, Chromosome Abnormalities. In: StatPearls. Treasure Island, USA: StatPearls Publishing; 2022.
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Confined placental mosaicism (CPM) - chromosomal abnormalities that are only present in tissue from the placenta, and are not present anywhere in the fetus itself.
Source: Toutain J, Goutte-Gattat D, Horovitz J, Saura R. Confined placental mosaicism revisited: Impact on pregnancy characteristics and outcome. PLoS One. 2018;13(4):e0195905. DOI: 10.1371/journal.pone.0195905.
C
Cell division - during the process of cell division, the chromosomes inside the cell are duplicated so that each daughter cell obtains a complete set of chromosomes after the whole process. With high maternal age, there is an increased amount of cell division errors, causing the chromosomes to be not properly divided among the two daughter cells. This can result in monosomy and trisomy.
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Source: Alberts B, Johnson A, Lewis J et al. Molecular Biology of the Cell. 6th ed. New York: Garland Science; 2015.
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Cell free (fetal) DNA – degraded DNA fragments shed into the bloodstream. Cell-free DNA (cfDNA) refers to different types of circulating DNA building blocks that are freely moving in the circulation, such as circulating tumor DNA, cell-free mitochondrial DNA (which is DNA from the energy-producing part of a cell) and cell-free fetal DNA (cffDNA) from the placenta during pregnancy.
Source: Gravina S, Sedivy JM, Vijg J. The dark side of circulating nucleic acids. Aging Cell. 2016 Jun;15(3):398-9. DOI: 10.1111/acel.12454.
Cervix - the lower, narrow part of the uterus (womb), connecting the uterus and the vagina. The cervix is also called the birth channel, because the baby exits the womb through this part.
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Source: Paulsen F, Waschke J (eds.). Internal Organs. 16th ed. Munich, Germany: Elsevier; 2018.
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Chorionic villus sampling - an invasive prenatal test in which bits of tissue called villi are removed from the placenta, after which the sample is tested for abnormalities. Read more about invasive prenatal testing here.
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Source: Jones TM, Montero FJ. Chorionic Villus Sampling. In: StatPearls. Treasure Island, USA: StatPearls Publishing; 2018.
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Chromatid - during the process of cell division, your chromosomes are duplicated so that they can be distributed equally over two new cells that contain the exact same genetic information. Until then, the duplicated chromosomes stay attached to the original ones. Both the original chromosome and the duplicated chromosome in a pair are referred to as a chromatid while they are attached.
Source: Wadsworth P, Titus J. Mitosis. In: Lennarz WJ, Lane MD (eds). Encyclopedia of Biological Chemistry. 2nd ed. Philadelphia, USA: Elsevier; 2013. p. 181-184.
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Chromosomal abnormalities - any structural or numerical abnormality of one or more chromosomes. This can involve aneuploidy, breakage of the chromosome, chromosomes having lost or exchanged big chunks, polyploidy (in which case a cell contains more than two copies of all chromosomes, for example four or eight copies of every chromosome) and more. These issues can happen in any chromosome, including the sex chromosomes. A person might be born with a chromosomal abnormality, which is referred to as a congenital abnormality. In this case, most of that person’s cells are typically affected. In other cases, a person develops the abnormality at some point in life. This is referred to as an acquired abnormality. In this case, only a small portion of a person’s cells are affected. What the effect of any given abnormality is, depends on which cells are affected, how many of them are affected, and in what way. This varies greatly between cases.
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Source: Queremel Milani DA, Tadi P. Genetics, Chromosome Abnormalities. In: StatPearls. Treasure Island, USA: StatPearls Publishing; 2022.
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Chromosome - your entire genetic code is subdivided into several separate DNA molecules, each of which forms one chromosome by becoming very tightly wound and by associating with proteins that help form this dense shape. This saves a lot of space compared to if your DNA was floating in your cells stretched out (in which case it is about two meters or six feet) – and it makes organization within the cell nucleus (where the DNA is) much easier. Each of your cells contains 46 chromosomes arranged in pairs – you inherited one of the pair from your father and one from your mother. Most of your chromosomes (22 pairs) are autosomal chromosomes; the last pair are your sex chromosomes.
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Source: Alberts B, Johnson A, Lewis J et al. Molecular Biology of the Cell. 4th ed. New York: Garland Science; 2002. and Queremel Milani DA, Tadi P. Genetics, Chromosome Abnormalities. In: StatPearls. Treasure Island, USA: StatPearls Publishing; 2022.
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Confined placental mosaicism (CPM) - chromosomal abnormalities that are only present in tissue from the placenta, and are not present anywhere in the fetus itself.
Source: Toutain J, Goutte-Gattat D, Horovitz J, Saura R. Confined placental mosaicism revisited: Impact on pregnancy characteristics and outcome. PLoS One. 2018;13(4):e0195905. DOI: 10.1371/journal.pone.0195905.
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DNA (deoxyribonucleic acid) - the substance in each of our cells that contains our genetic code. Each DNA molecule consists of two long strands, which wind around each other to form a helix-shaped structure. Each strand is mainly composed of four different building blocks (adenine, guanine, cytosine, and thymine), which are called nucleotides. Specific sequences of these building blocks, or nucleotides, tell the cell’s machinery exactly which proteins should be produced. Differences in people’s DNA are due to different sequences of nucleotides – which leads to differences in people’s appearance or how their body functions.
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Source: Alberts B, Johnson A, Lewis J et al. Molecular Biology of the Cell. 4th ed. New York: Garland Science; 2002.
E
Embryo - the correct medical term for the growing baby from conception up to and including week 8 (two months) of pregnancy.
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Source: Moore KL, Persaud TVN, Torchia MG. The Developing Human. 11th ed. Philadelphia, USA: Elsevier; 2020.
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Endometrium – the mucous cell layer that lines the uterus. It thickens throughout the menstrual cycle in preparation for embryo implantation, and is shed during menstruation.
Source: Marieb EN. Human Anatomy & Physiology. 5th ed. San Fransisco, USA: Benjamin Cummings; 2001.
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Extravillous trophoblast cells - special cells that develop from the placenta, that cause alterations in the structure of certain blood vessels in the uterus.
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Source: Moore KL, Persaud TVN, Torchia MG. The Developing Human. 11th ed. Philadelphia, USA: Elsevier; 2020.
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Fallopian tube - either of two tubes along which the eggs, produced by the ovaries, travel towards the uterus.
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Source: Marieb EN, Hoehn K. Human Anatomy & Physiology. 10th ed. Essex, UK: Pearson Education Limited; 2016.
Fetus - the correct medical term for the growing baby from the start of week 9 of pregnancy until birth.
Source: Moore KL, Persaud TVN, Torchia MG. The Developing Human. 11th ed. Philadelphia, USA: Elsevier; 2020.
Follicles – most people who can become pregnant have 300,000 to 400,000 small fluid filled sacs inside their ovaries, containing immature egg cells. During a typical menstrual cycle, one follicle releases one mature egg cell, which can then be fertilized.
Source: McGee EA, Hsueh AJW. Initial and Cyclic Recruitment of Ovarian Follicles. Endocrine Reviews. 2000;21(2):200-214. DOI: 10.1210/edrv.21.2.0394
G
Gestation - the age of a fetus counted from the first day of your last menstrual period.
Source: Moore KL, Persaud TVN, Torchia MG. The Developing Human. 11th ed. Philadelphia, USA: Elsevier; 2020.
G
Gestation - the age of a fetus counted from the first day of your last menstrual period.
Source: Moore KL, Persaud TVN, Torchia MG. The Developing Human. 11th ed. Philadelphia, USA: Elsevier; 2020.
H
Hormone - a molecule used by a body cell to send signals to other, far-away cells via the bloodstream. Hormones exist in different varieties. For example, estrogen and testosterone are fatty hormones made from cholesterol. Other hormones, such as adrenaline, are made from the building blocks of proteins (called amino acids). Different hormones can have different effects on different cells, or even on the same cell under different circumstances.
Source: Alberts B, Johnson A, Lewis J et al. Molecular Biology of the Cell. 6th ed. New York: Garland Science; 2015 and Molnar C, Gair J. Concepts of Biology – 1st Canadian Edition. BCcampus; 2015. Available from: https://opentextbc.ca/biology/
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Luteal phase – describes one of the phases of the menstrual cycle, after ovulation but before menstruation. During this phase, the lining of your uterus typically thickens in anticipation of a potential pregnancy. This lining is then shed during menstruation.
Source: Marieb EN, Hoehn K. Human Anatomy & Physiology. 10th ed. Essex, UK: Pearson Education Limited; 2016.
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Luteinizing hormone – a hormone in the human body, which triggers ovulation when present in high levels, and is important to keep an early pregnancy viable (meaning it prevents menstruation). Often abbreviated as LH.
Source: Marieb EN. Human Anatomy & Physiology. 5th ed. San Fransisco, USA: Benjamin Cummings; 2001.
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Monogenic diseases – these are rare diseases that are caused by an error in a single gene, such as cystic fibrosis. This is in contrast to polygenic diseases (most genetic diseases), which involve multiple genes. Monogenic diseases sometimes run in the family, because they can be transferred directly from parent to child when egg and sperm cells are made.
Source: Prakash V, Moore M, Yáñez-Muñoz RJ. Current Progress in Therapeutic Gene Editing for Monogenic Diseases. Mol Ther. 2016;24(3):465-74. DOI: 10.1038/mt.2016.5
N
NIPT - NIPT stands for non-invasive prenatal testing. It is a blood test that can be done during pregnancy to test for chromosomal abnormalities without the risk of harm to the baby. The test relies on DNA released from cells in the placenta, which are identical to the baby’s cells in most cases, into the pregnant person’s blood. Read more about NIPT here.
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Source: Goldwaser T, Klugman S. Cell-free DNA for the detection of fetal aneuploidy. Fertility and Sterility. 2018;109(2):195-200. DOI: 10.1016/j.fertnstert.2017.12.019
O
Ovaries - the ovaries are organs inside the pelvic cavity of most people with a female reproductive system. Typically, there is one on each side of the uterus. Each is connected to the uterus via a fallopian tube. The ovaries only produce eggs when you’re still a fetus in the womb – which means you’ll have all the eggs you’ll ever have by the time you’re born. These eggs then mature in your ovaries as you age. The ovaries also produce hormones such as estrogen and progesterone, which influence what your body looks like and how it functions.
Source: Marieb EN, Hoehn K. Human Anatomy & Physiology. 10th ed. Essex, UK: Pearson Education Limited; 2016.
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Ovulation - the process in which a mature egg cell is released from its follicle, under the influence of luteinizing hormone.
Source: Marieb EN, Hoehn K. Human Anatomy & Physiology. 10th ed. Essex, UK: Pearson Education Limited; 2016.
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Placenta - the placenta develops between the amniotic sac that holds the baby, and the lining of the uterus. It contains blood vessels that bring nutrients and oxygen to the baby from the circulation of the baby’s carrier and that remove waste from the baby’s circulation. The placenta is typically also delivered by the pregnant person, after delivery of the baby.
Source: Moore KL, Persaud TVN, Torchia MG. The Developing Human. 11th ed. Philadelphia, USA: Elsevier; 2020.
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Placenta disorders – describe a number of conditions which relate to diseases, disorders or dysfunction of the placenta during pregnancy. These can lead to pre-eclampsia, preterm delivery, premature rupture of membranes, or placental abruption (in which the placenta separates from the wall of the uterus before birth). Unfortunately, there is no treatment option to date – typically, the baby should be delivered soon.
Source: Parker SE, Werler MM. Epidemiology of ischemic placental disease: a focus on preterm gestations. Semin Perinatol. 2014;38(3):133-138. DOI: 10.1053/j.semperi.2014.03.004. and KosiÅ„ska-KaczyÅ„ska K. Placental Syndromes—A New Paradigm in Perinatology. International Journal of Environmental Research and Public Health. 2022; 19(12):7392. DOI: 10.3390/ijerph19127392
Pre-implantation Genetic Testing (PGT) – the genetic testing and examination of fertilized cells before they are implanted back into the uterus to avoid birth defects of the future child. This is used in assisted reproductive technologies (ART), which you can read more about here.
Source: Sullivan-Pyke C, Dokras A. Preimplantation Genetic Screening and Preimplantation Genetic Diagnosis. Obstetrics and Gynecology Clinics of North America. 2018;45(1):113–125. DOI:10.1016/j.ogc.2017.10.009.
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R
Respiratory distress syndrome - a disease in which the lungs do not have enough capacity to supply the organs in the human body with enough oxygen. This occurs mainly in babies that were born prematurely, because their lungs are underdeveloped.
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Source: Pramanik AK. Respiratory Distress Syndrome. In: Rosenkrantz T (ed.). Medscape. 2020. Available from: https://emedicine.medscape.com/article/976034-overview#a4 [Accessed September 3rd, 2022]
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Rhesus - the rhesus factor is a small protein (an antigen) on the surface of red blood cells. It can be present in several variations, but the most important variation in the context of pregnancy is the rhesus D factor, also written as Rh(D). If you have the Rh(D) antigen, you’re said to have a positive blood type. If you don’t, you have a negative blood type. This is indicated by adding a plus or a minus to the blood type. For example, if you have blood type A and you have the Rh(D) factor, you’re said to have blood type A+ (pronounced “A-positive”). Normally, it doesn’t matter whether you do or don’t have this Rh(D) factor. However, if you have a negative blood type and you’re pregnant with a baby that has a positive blood type, your body starts making antibodies against the Rh(D) factor. This is typically not a problem for your first pregnancy with an Rh(D)-positive baby. When you’re pregnant with a second Rh(D)-positive baby, your antibodies can start to attack that baby’s blood cells, which can make them very sick.
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Source: Source: Costumbrado J, Mansour T, Ghassemzadeh S. Rh Incompatibility. In: StatPearls. Treasure Island, USA: StatPearls Publishing; 2022.
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Sensitivity – sensitivity and specificity are measures of accuracy of a test. Sensitivity measures how many cases of disease a test can detect, out of all the people who actually have the disease who undergo the test. A test with high sensitivity can detect many or nearly all cases of disease (the so-called “true-positive” results, which are those cases in which the test indicates there is disease and there actually is) and only misses a few (the so-called “false-negative” results, which are those cases in which the test indicates there is no disease when there actually is disease). Therefore, highly sensitive tests have a high rate of true positives and a low rate of false negatives. This allows a physician to exclude disease based on a negative test result: if the test says there is no disease, this is highly likely to be true, because the test is so good at detecting when you’re sick. A test with (very) high sensitivity commonly has lower specificity, because it’s difficult for a test to be very good at detecting both sick and healthy people.
Source: Parikh R, Mathai A, Parikh S, Chandra Sekhar G, Thomas R. Understanding and using sensitivity, specificity and predictive values. Indian J Ophthalmol. 2008;56(1):45-50. DOI: 10.4103/0301-4738.37595
Sex chromosomes - the pair of chromosomes that determines your biological sex (usually XX for female and XY for male, but other variations can occur).
Source: Alberts B, Johnson A, Lewis J et al. Molecular Biology of the Cell. 6th ed. New York: Garland Science; 2015.
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Sequencing (DNA) - any technique used to determine the sequence of nucleotides in DNA (your genetic code) obtained from a sample of your blood or tissue. This allows the scientist performing the technique to detect abnormalities in your genes, which could be the cause of disease. If your whole genetic code (genome) is looked at, it’s called “whole genome sequencing”.
Source: Heather JM, Chain B. The sequence of sequencers: The history of sequencing DNA. Genomics. 2016;107(1):1-8. DOI: 10.1016/j.ygeno.2015.11.003
Screening - a method of testing for disease or abnormalities that is designed to detect as many cases of this disease or abnormality as possible. However, because of this, screenings will commonly give a positive result (that is, indicate that a person has the disease) even when a person does not have the disease. This is called a false-positive result. This characteristic makes screenings unsuitable for confirming a diagnosis, but they are a great tool for deciding who needs further, often more intensive or invasive testing. In other words, screenings indicate an increased risk of a disease or abnormality, not a definitive diagnosis.
Source: Maxim LD, Niebo R, Utell MJ. Screening tests: a review with examples. Inhalation Toxicology. 2014;26(13):811-828. DOI: 10.3109/08958378.2014.955932
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Specificity - sensitivity and specificity are measures of accuracy of a test. Specificity measures how many healthy people a test can detect, out of all the people who are actually healthy who undergo the test. A test with high specificity can detect many or nearly all healthy people (the so-called “true-negative” results, which are those cases in which the test indicates there is no disease and there actually isn’t) and only misses a few (the so-called “false-positive” results, which are those cases in which the test indicates there is disease when there actually isn’t). Therefore, highly specific tests have a high rate of true negatives and a low rate of false positives. This allows a physician to confirm disease based on a positive test result: if the test says there is disease, this is highly likely to be true, because the test is so good at detecting when you’re healthy. A test with (very) high specificity commonly has low sensitivity, because it’s difficult for a test to be very good at detecting both sick and healthy people.
Source: Parikh R, Mathai A, Parikh S, Chandra Sekhar G, Thomas R. Understanding and using sensitivity, specificity and predictive values. Indian J Ophthalmol. 2008;56(1):45-50. DOI: 10.4103/0301-4738.37595
S
Sensitivity – sensitivity and specificity are measures of accuracy of a test. Sensitivity measures how many cases of disease a test can detect, out of all the people who actually have the disease who undergo the test. A test with high sensitivity can detect many or nearly all cases of disease (the so-called “true-positive” results, which are those cases in which the test indicates there is disease and there actually is) and only misses a few (the so-called “false-negative” results, which are those cases in which the test indicates there is no disease when there actually is disease). Therefore, highly sensitive tests have a high rate of true positives and a low rate of false negatives. This allows a physician to exclude disease based on a negative test result: if the test says there is no disease, this is highly likely to be true, because the test is so good at detecting when you’re sick. A test with (very) high sensitivity commonly has lower specificity, because it’s difficult for a test to be very good at detecting both sick and healthy people.
Source: Parikh R, Mathai A, Parikh S, Chandra Sekhar G, Thomas R. Understanding and using sensitivity, specificity and predictive values. Indian J Ophthalmol. 2008;56(1):45-50. DOI: 10.4103/0301-4738.37595
Sex chromosomes - the pair of chromosomes that determines your biological sex (usually XX for female and XY for male, but other variations can occur).
Source: Alberts B, Johnson A, Lewis J et al. Molecular Biology of the Cell. 6th ed. New York: Garland Science; 2015.
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Sequencing (DNA) - any technique used to determine the sequence of nucleotides in DNA (your genetic code) obtained from a sample of your blood or tissue. This allows the scientist performing the technique to detect abnormalities in your genes, which could be the cause of disease. If your whole genetic code (genome) is looked at, it’s called “whole genome sequencing”.
Source: Heather JM, Chain B. The sequence of sequencers: The history of sequencing DNA. Genomics. 2016;107(1):1-8. DOI: 10.1016/j.ygeno.2015.11.003
Screening - a method of testing for disease or abnormalities that is designed to detect as many cases of this disease or abnormality as possible. However, because of this, screenings will commonly give a positive result (that is, indicate that a person has the disease) even when a person does not have the disease. This is called a false-positive result. This characteristic makes screenings unsuitable for confirming a diagnosis, but they are a great tool for deciding who needs further, often more intensive or invasive testing. In other words, screenings indicate an increased risk of a disease or abnormality, not a definitive diagnosis.
Source: Maxim LD, Niebo R, Utell MJ. Screening tests: a review with examples. Inhalation Toxicology. 2014;26(13):811-828. DOI: 10.3109/08958378.2014.955932
​
Specificity - sensitivity and specificity are measures of accuracy of a test. Specificity measures how many healthy people a test can detect, out of all the people who are actually healthy who undergo the test. A test with high specificity can detect many or nearly all healthy people (the so-called “true-negative” results, which are those cases in which the test indicates there is no disease and there actually isn’t) and only misses a few (the so-called “false-positive” results, which are those cases in which the test indicates there is disease when there actually isn’t). Therefore, highly specific tests have a high rate of true negatives and a low rate of false positives. This allows a physician to confirm disease based on a positive test result: if the test says there is disease, this is highly likely to be true, because the test is so good at detecting when you’re healthy. A test with (very) high specificity commonly has low sensitivity, because it’s difficult for a test to be very good at detecting both sick and healthy people.
Source: Parikh R, Mathai A, Parikh S, Chandra Sekhar G, Thomas R. Understanding and using sensitivity, specificity and predictive values. Indian J Ophthalmol. 2008;56(1):45-50. DOI: 10.4103/0301-4738.37595
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Thrombosis – describes a condition in which blood forms clots and blocks blood vessels. Typical symptoms include pain, swelling, redness, warmth, and numbness in the affected area, commonly the legs. This can happen under all sorts of circumstances, and is also more common in pregnancy. It is important that you contact a medical professional immediately when experiencing these symptoms, because complications of thrombosis can be life-threatening (including difficulty breathing and stroke).
Source: Marieb EN. Human Anatomy & Physiology. 5th ed. San Fransisco, USA: Benjamin Cummings; 2001.
Trimester - a period of around three months, approximately one-third of a normal pregnancy. The first trimester is up to 12 weeks of pregnancy. The second trimester runs from 12 to 27 weeks. The third trimester runs from 28 to 40 weeks. Some authorities go by slightly different week cut-offs.
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Source: Moore KL, Persaud TVN, Torchia MG. The Developing Human. 11th ed. Philadelphia, USA: Elsevier; 2020.
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Ultrasound analysis - an examination that uses sound waves and accompanying echoes to visualize the body’s internal structures. A cold-feeling gel is put on the skin beforehand, which helps direct the sound waves and optimizes picture quality.
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Source: Morgan MA, Bell DJ. Ultrasound (introduction). Available from: https://radiopaedia.org/articles/32088 [Accessed September 3rd, 2022]
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Uterus - an organ in the pelvic cavity of most people with a female reproductive system. This organ is connected to the vagina via its lowest and narrowest portion: the cervix. The uterus has a strong, muscular wall lined on the inside by thinner, slippery layers of cells (the endometrium). Most of the endometrium is shed during menstruation, and is built back up afterwards. The endometrium is also the layer in which a fertilized egg implants after about a week of pregnancy. During pregnancy, the fetus grows inside a fluid-filled sac (the amniotic sac) inside the uterus. The muscular wall of the uterus contracts during menstruation, which can be felt as cramping, and causes the contractions you feel during labor.
Source: Marieb EN, Hoehn K. Human Anatomy & Physiology. 10th ed. Essex, UK: Pearson Education Limited; 2016.
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Ultrasound analysis - an examination that uses sound waves and accompanying echoes to visualize the body’s internal structures. A cold-feeling gel is put on the skin beforehand, which helps direct the sound waves and optimizes picture quality.
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Source: Morgan MA, Bell DJ. Ultrasound (introduction). Available from: https://radiopaedia.org/articles/32088 [Accessed September 3rd, 2022]
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Uterus - an organ in the pelvic cavity of most people with a female reproductive system. This organ is connected to the vagina via its lowest and narrowest portion: the cervix. The uterus has a strong, muscular wall lined on the inside by thinner, slippery layers of cells (the endometrium). Most of the endometrium is shed during menstruation, and is built back up afterwards. The endometrium is also the layer in which a fertilized egg implants after about a week of pregnancy. During pregnancy, the fetus grows inside a fluid-filled sac (the amniotic sac) inside the uterus. The muscular wall of the uterus contracts during menstruation, which can be felt as cramping, and causes the contractions you feel during labor.
Source: Marieb EN, Hoehn K. Human Anatomy & Physiology. 10th ed. Essex, UK: Pearson Education Limited; 2016.
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