Twins
Two individuals derived from two FETUSES that were fertilized at or about the same time, developed in the UTERUS simultaneously, and born to the same mother. Twins are either monozygotic (TWINS, MONOZYGOTIC) or dizygotic (TWINS, DIZYGOTIC).
Diseases in Twins
Disorders affecting TWINS, one or both, at any age.
Twins, Monozygotic
Twins, Conjoined
Conjoined twins are a rare type of monozygotic twinning where genetically identical individuals form a single organism with varying degrees of physical connection and shared anatomy due to incomplete division during embryonic development.
Twins, Dizygotic
Twin Studies as Topic
Methods of detecting genetic etiology in human traits. The basic premise of twin studies is that monozygotic twins, being formed by the division of a single fertilized ovum, carry identical genes, while dizygotic twins, being formed by the fertilization of two ova by two different spermatozoa, are genetically no more similar than two siblings born after separate pregnancies. (Last, J.M., A Dictionary of Epidemiology, 2d ed)
Pregnancy, Twin
The condition of carrying TWINS simultaneously.
Fetofetal Transfusion
Passage of blood from one fetus to another via an arteriovenous communication or other shunt, in a monozygotic twin pregnancy. It results in anemia in one twin and polycythemia in the other. (Lee et al., Wintrobe's Clinical Hematology, 9th ed, p737-8)
Pregnancy
Triplets
Pregnancy Reduction, Multifetal
Selective abortion of one or more embryos or fetuses in a multiple gestation pregnancy. The usual goal is to improve the outcome for the remaining embryos or fetuses.
Environment
Gestational Age
The age of the conceptus, beginning from the time of FERTILIZATION. In clinical obstetrics, the gestational age is often estimated as the time from the last day of the last MENSTRUATION which is about 2 weeks before OVULATION and fertilization.
Chorion
The outermost extra-embryonic membrane surrounding the developing embryo. In REPTILES and BIRDS, it adheres to the shell and allows exchange of gases between the egg and its environment. In MAMMALS, the chorion evolves into the fetal contribution of the PLACENTA.
Pregnancy Outcome
Results of conception and ensuing pregnancy, including LIVE BIRTH; STILLBIRTH; SPONTANEOUS ABORTION; INDUCED ABORTION. The outcome may follow natural or artificial insemination or any of the various ASSISTED REPRODUCTIVE TECHNIQUES, such as EMBRYO TRANSFER or FERTILIZATION IN VITRO.
Genetics, Behavioral
Ultrasonography, Prenatal
The visualization of tissues during pregnancy through recording of the echoes of ultrasonic waves directed into the body. The procedure may be applied with reference to the mother or the fetus and with reference to organs or the detection of maternal or fetal disease.
Birth Weight
Gene-Environment Interaction
Twinning, Monozygotic
Social Environment
Registries
Fetoscopy
Quadruplets
Polyhydramnios
A condition of abnormally high AMNIOTIC FLUID volume, such as greater than 2,000 ml in the LAST TRIMESTER and usually diagnosed by ultrasonographic criteria (AMNIOTIC FLUID INDEX). It is associated with maternal DIABETES MELLITUS; MULTIPLE PREGNANCY; CHROMOSOMAL DISORDERS; and congenital abnormalities.
Denmark
Dermatoglyphics
Genetic Predisposition to Disease
Reproductive Techniques, Assisted
Phenotype
The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.
Twin Study
A 'Twin Study' is an epidemiological research design that compares monozygotic (identical) and dizygotic (fraternal) twins to estimate the heritability of traits, diseases, or behaviors by examining the concordance rates between them.
Sweden
Byzantium
An ancient city, the site of modern Istanbul. From the 4th to 15th centuries the empire extended from southeastern Europe to western Asia, reaching its greatest extent under Justinian (527-565). By about 1000 A.D. it comprised the southern Balkans, Greece, Asia Minor, and parts of southern Italy. The capture of Constantinople in 1453 marked the formal end of the Byzantine Empire. (From Webster's New Geographical Dictionary, 1988)