Multiple Births Medical Definitions | Twin Pregnancy & Multiple Births | Twin Tips | Resources Centre | Twins UK

The list below are the commonly used medical terms in multiple pregnancies.

Amnion: Inner lining of sac containing the developing fetus.

Amniocentesis: Removal of a portion of amniotic fluid. either to test for chromosomal abnormalities that could indicate Down Syndrome or other disorders. or to relieve polyhydromnios.

Caesarean Section (C-section): Surgical method of childbirth in which a woman's abdomen and uterus are incised and the baby is delivered transabdominally.

Chorion: Outer lining of sac containing the developing fetus.

Conjoined Twins: Monozygotic twins where separation into two individuals is incomplete so their bodies are joined together at some point.

Cryptophasia: The secret language of twins (also know as Idioglossia)

Diamniotic Twins: Twins who have developed in separate amniotic sacs. These twins may be either dizygotic (fraternal) or monozygotic (identical).

Dichorionic Twins: Twins who have developed in separate chorionic sacs. These twins may be either dizygotic or monozygotic.

Dizygotic (Or dizygous) Twins: Twins formed from two separate zygotes. Commonly known as "fraternal twins."

Embryo: The developing baby during the first eight weeks of pregnancy.

Embryo Reduction: See Fetal Reduction (also known as selective reduction).

Epidural: Anesthetic injected in a space at the base of the spinal cord.

Fetal Reduction: The reduction of the number of viable fetuses/embryos in a multiple pregnancy (usually within a higher order multiple pregnancy) by medical intervention. Also referred to as multi-fetal reduction or selective reduction.

Fetus Papyraceous: A fetus which dies in the second trimester of pregnancy and becomes compressed and parchment-like.

Fraternal Twins: See Dizygotic Twins.

GIFT: Gamete Intrafallopian Transfer - assisted conception method.

Higher Order Multiples: Triplets. quadruplets. quintuplets or more. Also known as Supertwins within the multiples community.

Identical Twins: See monozygotic twins.

IVF: In vitro fertilization and embryo transfer - assisted conception method.

Intrauterine Growth Retardation: Impeded or delayed fetal development and maturation due to genetic factors. maternal disease or fetal malnutrition caused by placental insufficiency.

Monoamniotic Twins: Twins who have developed in a single amniotic sac. These twins are always monozygotic.

Monochorionic Twins: Twins who have developed in a single chorionic sac. These twins are always monozygotic.

Monozygotic (or monozygous) Twins: Twins formed from a single zygote. Commonly known as "identical twins."

Multifetal Pregnancy Reduction: See Fetal Reduction.

Multiple Pregnancy: A pregnancy with more than one fetus.

Neonatal Death: A death within the first four weeks after delivery.

Neonatal Intensive-care Unit (NICU): Hospital unit containing special equipment for the management and care of premature and seriously ill newborns.

Oxytocin: Hormone prescribed to stimulate contractions in order to induce or augment labour and to contract the uterus to control postpartum bleeding. Pitocin is a trademarked name for oxytocin. Oxytocin also causes contractions within the breasts which squeeze the milk down the ducts to the nipples so the baby can feed.

Placenta: Vascular organ through which fetus receives oxygen. nutrients and antibodies to infection and excretes carbon dioxide and waste products.

Premature/Prematurity: Delivery before 37 completed weeks of pregnancy in a multiple pregnancy.

Prolactin: Milk-producing hormone released by the pituitary gland in response to a baby's sucking.

Polyhydramnios: Abnormal condition of pregnancy characterized by excess of amniotic fluid.

Preclampsia: Abnormal condition of pregnancy characterized by the onset of acute hypertension after the twenty-fourth week of gestation. Increased chance during first time multiple birth.

Preterm: See Premature.

Selective Fetocide: The medical destruction of one or more fetuses in a continuing pregnancy.

Selective Reduction: See Fetal Reduction.

Singleton: Child born from a non-multiple pregnancy.

SCBU: Special Care Baby Unit: See NICU

Stillbirth: A baby born at 20 weeks gestation or later. who shows no sign of life.

Superfecundation: Conception of multiples as a result of two acts of sexual intercourse in the same menstrual cycle.

Superfetation: Conception of multiples as a result of two acts of sexual intercourse in different menstrual cycles.

Toxemia: Hypertensive disorder of pregnancy including presence of bacterial toxins in the bloodstream; also called preclampsia.

Trizygotic: Fetuses formed from three separate zygotes (triplets).

Twin-to-Twin Transfusion Syndrome (TTTS): A condition in which blood from one monozygotic twin fetus transfuses into the other fetus via blood vessels in the placenta. Can also occur among monozygotic multiples in a higher order multiple pregnancy.

VBAC: Vaginal birth after caesarean.

Vanishing Twin Syndrome: Unexplained loss of one multiple fetus during the first trimester. despite the survival of other(s).

Zygosity: Describing the genetic makeup of children from a multiple birth.

Zygote: Fertilized egg.