Twin pregnancy types!!!!!

Twin Pregnancy Types

• Normal Twins

• Co-joined Twins

Normal Twins

The Normal Twins pregnancy is classified into two types

1. Identical twins
2. Fraternal twins

Identical Twins

• Identical twins come from a single egg that has been fertilized by one sperm. For unknown reasons, the fertilized egg splits into two embryos during the first stage of development. 
• In the mother's womb (uterus), most identical twins share the same placenta. (They get oxygen and nutrients from the mother and get rid of wastes through the placenta.) But they usually grow within separate amniotic sacs. 
• In rare cases, identical twins share one amniotic sac.

Twins Types

Fraternal Twins

• Fraternal twins develop when two eggs are fertilized by two separate sperms. 
• The fetuses have separate placentas and amniotic sacs.

Co-joined Twins

Conjoined twins are monozygotic twins who are joined at some region of their bodies.

The Cojoined Twins pregnancy is classified into four types

1. Terata Catadidyma
2. Terata Anacatadidyma
3. Parasitic twinning
4. Fetus in fetu

The many different types of conjoined twins are classified by the area where the attachment is located:

Terata Catadidyma

It refers to twins joined in the lower portion of their body, or they may appear to be two bodies on top and one body on the bottom.

Types

• Pygopagus - back-to-back, joined at the rump (about 19 percent)
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• Ischiopagus - joined sacrum to sacrum (about six percent)
• Dicephalus - one body with two separate heads
• Diprosopus - single body and head, but bearing two faces

Terata Anadidyma

Terata Anadidyma refers to twins with one single upper body with a double lower half or twins who are connected by a single body part.

                                                             Terata Anadidyma

• Cephalopagus - connected at the head (about two percent)
• Syncephalus - connected in the facial region
• Cephalothoracopagus - connected in the facial region and at the thorax
• Dipygus - one upper body with two lower bodies (including the abdomen, pelvis and legs)

Terata Anacatadidyma 

Terata Anacatadidyma refers to twins who are joined somewhere along the midsection of the body.

Thoracopagus - joined at the chest; may share a single heart or have some cardiac connection; some organs in the abdominal region may be malformed (about 40 percent)

                                                              Terata Anacatadidyma

Omphalopagus - joined at the chest (about 33 percent)

Rachipagus - back-to-back, joined along the spine above the sacrum

Parasitic Twinning

Parasitic twinning is when one conjoined twin is much smaller and perhaps not as fully formed or developed as the larger twin. In rare instances, this results in limbs located in bizarre areas of a twin's body. 

For example, what appears to be a singleton birth arrives with an arm joined at his back or an additional leg joined at the hip region.

Fetus in fetu

Fetus in fetu is when a malformed twin is discovered inside the body of a host twin -- a living child or adult. Although it would be difficult to know the exact rate of incidence (as there may be cases that go undiscovered for long periods of time), it is believed that fetus in fetu occurs once in every 500,000 live births. 

In "Fetus In Fetu: A Case Report," Phatak, Kolwadkar and Phatak state: "Masses containing bones, cartilage, teeth, central nervous system tissue, fat and muscle may be found in the abdomen of newborns and children termed `Teratomas'. They are defined as fetus in fetu if there is a recognized trunk and limbs."