MiscarriageMiscarriage, also known in medical terms as a spontaneous abortion, is the death and expulsion of an embryo or fetus before it is able to survive independently. The term miscarriage is sometimes used to refer to all forms of pregnancy loss and pregnancy with abortive outcome before 20 weeks of gestation. Miscarriage before 6 weeks of gestation is defined by ESHRE as biochemical loss. Once ultrasound or histological evidence shows that a pregnancy has existed, the used term is clinical miscarriage, which can be early before 12 weeks and late between 12–21 weeks.
HeritabilityHeritability is a statistic used in the fields of breeding and genetics that estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population. The concept of heritability can be expressed in the form of the following question: "What is the proportion of the variation in a given trait within a population that is not explained by the environment or random chance?" Other causes of measured variation in a trait are characterized as environmental factors, including observational error.
Menstrual cycleThe menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that makes pregnancy possible. The ovarian cycle controls the production and release of eggs and the cyclic release of estrogen and progesterone. The uterine cycle governs the preparation and maintenance of the lining of the uterus (womb) to receive an embryo. These cycles are concurrent and coordinated, normally last between 21 and 35 days, with a median length of 28 days, and continue for about 30–45 years.
StillbirthStillbirth is typically defined as fetal death at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life. A stillbirth can often result in the feeling of guilt or grief in the mother. The term is in contrast to miscarriage, which is an early pregnancy loss, and Sudden Infant Death Syndrome, where the baby dies a short time after being born alive. Often the cause is unknown.
Birth defectA birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can range from mild to severe. Birth defects are divided into two main types: structural disorders in which problems are seen with the shape of a body part and functional disorders in which problems exist with how a body part works. Functional disorders include metabolic and degenerative disorders.
Trisomy XTrisomy X, also known as triple X syndrome and characterized by the karyotype 47,XXX, is a chromosome disorder in which a female has an extra copy of the X chromosome. It is relatively common and occurs in 1 in 1,000 females but it is rarely diagnosed; fewer than 10 per cent of those with the condition know they have it. Those who have symptoms can have learning disabilities, mild dysmorphic features such as hypertelorism (wide-spaced eyes) and clinodactyly (incurved little fingers), early menopause, and increased height.
AnovulationAnovulation is when the ovaries do not release an oocyte during a menstrual cycle. Therefore, ovulation does not take place. However, a woman who does not ovulate at each menstrual cycle is not necessarily going through menopause. Chronic anovulation is a common cause of infertility. In addition to the alteration of menstrual periods and infertility, chronic anovulation can cause or exacerbate other long-term problems, such as hyperandrogenism or osteopenia. It plays a central role in the multiple imbalances and dysfunctions of polycystic ovary syndrome.
Conjoined twinsConjoined twins – popularly referred to as Siamese twins – are twins joined in utero. It is a very rare phenomenon, estimated to occur in anywhere between one in 49,000 births to one in 189,000 births, with a somewhat higher incidence in Southwest Asia and Africa. Approximately half are stillborn, and an additional one-third die within 24 hours. Most live births are female, with a ratio of 3:1. Two possible explanations of the cause of conjoined twins have been proposed.
Turner syndromeTurner syndrome (TS), also known as 45,X, or 45,X0, is a genetic disorder in which a female has a single X chromosome, compared to the two sex chromosomes (XX or XY) in most people. Signs and symptoms vary among those affected. Often, a short and webbed neck, low-set ears, low hairline at the back of the neck, short stature, and swollen hands and feet are seen at birth. Typically, those affected do not develop menstrual periods or breasts without hormone treatment and are unable to have children without reproductive technology.
Genome-wide association studyIn genomics, a genome-wide association study (GWA study, or GWAS), is an observational study of a genome-wide set of genetic variants in different individuals to see if any variant is associated with a trait. GWA studies typically focus on associations between single-nucleotide polymorphisms (SNPs) and traits like major human diseases, but can equally be applied to any other genetic variants and any other organisms. When applied to human data, GWA studies compare the DNA of participants having varying phenotypes for a particular trait or disease.
