Conjoined twins are two identical babies with fused body parts at the time of birth.
Conjoined twins occur due to incomplete separation of the fertilized embryo. The embryo separates into two fetuses but remain physically connected even after birth.
The common sites of connection are the chest, pelvis or buttocks. Most often, conjoined twins share one or more internal organs. Stillbirth and death shortly after birth are common occurrences in case of conjoined twins.
After birth, the conjoined twins can be surgically separated. Success of the surgery depends on the site of connection and extent of shared organs between the twins.
Also, experience and skill of the surgical team play a major role in outcome of the surgery.
A woman carrying conjoined twins may not show any specific signs or symptoms. The signs are similar to those in women having normal twins. More than normal growth of uterus and excessive fatigue, nausea and vomiting can be experienced early in the pregnancy.
On the basis of where they are connected, conjoined twins are classified into:
Thoracopagus twins: These twins have fused chest and have a common heart. In some cases, liver and upper intestine may also be shared.
Omphalopagus twins: These twins have connections near bellybutton. Majority of omphalopagus twins have a common liver, and some share the lower part of the small intestine (ileum) and colon.
Pygopagus twins: These twins join at the base of the spine and commonly face away from one another. In some cases, the lower digestive tract may be fused and in few, genito-urinary organs may be shared.
Ischiopagus twins: These twins have fused pelvis. In many cases, lower digestive tract, liver and genito-urinary organs are shared.
Craniopagus twins: These twins are connected at the head. They have a shared skull and possibly shared brain tissues. Commonly there is sharing of the cerebral cortex, the part of the brain associated with memory, language and perception. Rarely, an underdeveloped twin may be connected to a fully formed twin (asymmetrical conjoined twins).
What exactly causes conjoined twins is still unclear.
Identical twins, also called monozygotic twins, as the name suggests refer to two identical twins that develop when a single fertilized egg (mono zygote) splits and forms two embryos.
Conjoined twins are probably formed if the embryo splits later than 12 days after conception, the time when embryonic layers have already begun to differentiate into specific organs and structures. The split is interrupted resulting into conjoined twins.
Another theory suggests during early development, two separate embryos fuse together to form conjoined twins,
4 Making a Diagnosis
Using standard ultrasound as early as the first three months of pregnancy can help you diagnose conjoined twins.
If you want to learn more about your twins like how their organs are functioning, your doctor may recommend ultrasounds and echocardiograms about halfway through pregnancy.
However, if the identical twins share a common amniotic sac, a false-positive result may be produced.
To obtain details on the site of connection and involvement of the shared organs, an MRI scan may be used after detection by an ultrasound.
The treatment for conjoined twins depends on the health of the conjoined twins, site of their connection and organs shared between them. A woman with conjoined twins is kept under close and continuous supervision by a team of doctors throughout the pregnancy. This helps the doctors to learn more about the twins' anatomy, functional capabilities and prognosis after birth which in turn will help them to design specific treatment plans.
Delivery by C-section is a must for every case of conjoined twins, which is planned two to four weeks before the due date.
After birth of the conjoined twins, surgery to separate them is seriously assessed. In case one of the twins dies, separation surgery is needed immediately to avoid complications. In general, separation surgery is a non-emergency procedure done two to four months after birth.
Do you need a separation surgery
The decision to go for a separation surgery is essentially a difficult one as it is associated with health of the mother and both the twins. The consequences of the decision do not end here as the decision will impact entire life of the twins even when they are separated. It requires a lot of judgement and consultation with experts to take this vital decision.
Following questions may help you go for a wise and far sighted decision:
Do the twins share vital organs?
Are the twins healthy enough to withstand separation surgery?
What are the odds of successful separation?
What type of reconstructive surgery might be needed for each twin after successful separation?
What issues would the twins face if left conjoined?
6 Lifestyle and Coping
Lifestyle modifications are necessary in order to cope with conjoined twins.
Acknowledging that your unborn children have a life-threatening condition requires a lot of courage. The parents are under tremendous pressure and emotional stress when deciding what to do and predicting what future effects the decision will have.
As the cases of conjoined twins are uncommon, parents have difficulty finding the resources for conjoined twins.
You may learn more about the condition through various organizations working in this sector.
7 Risks and Complications
The risk of fatality in conjoined twins is very high.
Conjoined twins are still a sort of mystery to the scientific community. It has been observed that Latin America has greater incidence of conjoined twins as compared to the United States or Europe.
Most conjoined twins die in the womb (stillborn) or shortly after birth. Delivery by cesarean section is a must for conjoined twins.
Approximately half of the conjoined twins are dead at the time of birth.
Even when the conjoined twins are born alive, less than half survive long enough to be considered for separation surgery.
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