The first record of conjoined twins is a statue dating from 6500 B.C displaying the “double goddess.”  Conjoined twins occur rarely, with an incidence of 1 in 50,000-100,000 pregnancies.  Unfortunately, about 60% of conjoined twins die either in the womb or after birth, making the incidence only about 1 in 200,000 live births. The prospect of giving birth to conjoined twins can be a very frightening situation for expecting moms. Families who are expecting conjoined twins often face ethical dilemmas after delivery in order to ensure the health and well-being of both of their babies.
How are conjoined twins formed?
Conjoined twins are when two identical twins are physically connected at birth.  They can be connected at the chest, abdomen, pelvis, spine, or head. Sometimes, conjoined twins also share one or more internal organs. There are 2 theories for how conjoined twins form. Normally, identical twins develop when a fertilized egg divides during the first 2 weeks of conception into 2 separate fertilized eggs. It is thought that with conjoined twins, division of the fertilized egg does not occur until after the first 2 weeks of conception, and the second fertilized egg does not fully separate.  Another theory states that conjoined twins may develop from 2 fertilized eggs that were originally separate and later joined together.  In both cases, the 2 fertilized eggs that are not fully separated will develop into 2 babies that are physically joined.
How do I know if I am pregnant with conjoined twins?
Your doctor can determine if you are expecting conjoined twins with an ultrasound at the end of your first trimester.  About halfway through your pregnancy, more detailed ultrasounds and echocardiograms can be used to determine the extent that the twins are connected and how their organs are functioning. If conjoined twins are confirmed with an ultrasound, an MRI may be used to provide more detail about where the twins are joined and which organs are shared.
What is the outlook for conjoined twins?
The outlook for conjoined twins depends largely on where the babies are joined. Many conjoined twins will die either in the womb or shortly after delivery. Some conjoined twins survive and can be separated with surgery. The success at surgically separating conjoined twins is dependent on the skills of the surgeons, the location where the twins are joined, and the organs that are shared between the twins. Other conjoined twins may not be able to be separated, especially cases that involve sharing of the heart or brain.
What can be done to save them?
Conjoined twins that survive delivery will be assessed to determine if surgical separation is possible. In some cases, it is not medically recommended to separate twins, or parents may not agree to separation.  If, after birth, one of the twins is dying or his or her condition is threatening the survival of the other twin, emergency surgery may be required to immediately separate the twins and save the life of one or both. In cases where the twins are stable after birth, delaying separation by 2 to 4 months is preferred.  This allows the twins to grow past the critical time after delivery and increase the likelihood of surviving separation surgery.  During this time, the medical team will conduct a series of tests and preoperative studies to prepare for the surgery and plan a course of action that will be most beneficial to the twins. Conjoined twins who do not require immediate separation are more likely to survive. It has been shown that twins requiring immediate separation have only a 30% survival rate, compared to 80% for twins who do not.
The goal of separation surgery is to save the lives of the twins and to improve their quality of life. However, some nonseparated twins can still have successful and productive lives. An example is the case of Eng and Chang Bunker, born in 1811, who both lived unseparated to the age of 63. The decision of whether to have conjoined twins separated is one that you will need to discuss with your doctor and the medical team after delivery. Your doctor will assess the complications involved with the surgery and discuss the likelihood of success and potential risks to both twins.
If you are expecting conjoined twins, your doctor will closely monitor you and your babies throughout pregnancy. You will likely be referred to many different specialists who will try to learn about the anatomy of both twins and their outlook. Together with the help of your medical team, you can make the most appropriate treatment decision that will benefit the health and well-being of your twins.
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