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This list of
terms is provided for your information. Please
consult with your physician if you require a more
detailed explanation of any of these terms.
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Conjoined twins -
Identical twins where separation is incomplete so their
bodies are joined together at some point. Conjoined twins
are sometimes referred to as "Siamese twins."
Diamniotic twins -
Twins who have developed in separate amniotic sacs. These
twins may be either dizygotic or monozygotic.
Dichorionic twins -
Twins who have developed in separate chorionic sacs. These
twins may be either dizygotic or monozygotic.
Dizygotic (dizygous)
twins - Twins formed from two separate zygotes.
Dizygotic twins are commonly referred to as "fraternal
twins."
Embryo reduction -
See fetal reduction.
Fetal reduction -
See Multifetal Pregnancy Reduction
Feto-fetal transfusion
syndrome - See Twin to Twin Transfusion Syndrome (TTTS).
Fetus papyraceous -
A fetus that dies in the second three months of pregnancy
and becomes compressed and parchment-like.
Fraternal twins -
See Dizygotic twins.
Higher-order multiples
- Triplets, quadruplets, quintuplets or more.
Higher-order pregnancy
- A pregnancy with three or more fetuses.
Identical twins -
See Monozygotic twins.
Infant death - Death
in the first year of life.
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 (monozygous)
twins - Twins formed from a single zygote. Monozygotic
twins are commonly referred to as "identical
twins."
Multifetal Pregnancy
Reduction - The reduction in number of viable
fetuses/embryos in a multiple (usually higher multiple)
pregnancy by medical intervention.
Multiple pregnancy -
A pregnancy with more than one fetus.
Neonatal death - A
death in the first four weeks after delivery.
Perinatal mortality
- A stillbirth or death during the first week after
delivery.
Selective fetocide -
The medical destruction of one or more fetuses in a
continuing pregnancy.
Selective reduction
- See Fetal reduction.
Siamese twins - See
conjoined twins.
Stillbirth - A baby
born at 24 weeks gestation or later who shows no signs of
life.
Superfecundation -
Conception of twins as a result of two acts of sexual
intercourse in the same menstrual cycle.
Superfetation -
Conception of twins as a result of two acts of sexual
intercourse in different menstrual cycles.
Supertwins - Higher
order multiples: triplets, quadruplets, quintuplets or more.
Trizygotic - Formed
from three separate zygotes.
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. This condition can also occur
among monozygotic multiples in a higher-order multiple
pregnancy.
Vanishing twin syndrome
- The reabsorption of one multiple fetus early in the
pregnancy, usually by the twelfth gestational week.
Zygosity - The
genetic relationship between or among children from a
multiple birth (i.e., whether the children are monozygotic
or dizygotic multiples).
Zygosity testing -
Testing done to determine the zygosity of children from a
multiple birth. The only completely reliable form of
zygosity testing is DNA fingerprinting.
Zygote - A
fertilized ovum.
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