The medical journal, Fertility and Sterility has reported a case of conjoined twins after ovarian stimulation and Intra Cytoplasmic Sperm Injection (ICSI), which is a rare occurrence.
A 32 year old woman had ICSI at a private fertility clinic and had three embryos implanted. This resulted in a positive pregnancy test so she had an ultrasound scan at six weeks and four days of pregnancy. An embryo was seen that measured around seven weeks, large for its age. Due to the abnormal size of the embryo, a further scan was done two weeks later and two foetuses and one heart were seen. At 10 weeks of pregnancy, a third scan was done and two foetuses with two hearts were seen. The foetuses were attached at the thorax (Greek for breastplate, meaning the babies were joined facing each other, chest to chest). It is the most common type of conjoined twins. Doctors diagnosed thoracopagus. The mother elected to end the pregnancy.
ICSI as a Role for Conjoined Twins
The authors of the case report suggested that assisted reproductive technologies including ICSI may be partially responsible for some cases of conjoined twinning.
‘Conjoined twins conceived through assisted reproduction are extremely rare. This case suggests that ovulation induction, ICSI, and assisted hatching may also play roles in addition to other factors commonly proposed to be responsible for conjoined twining, such as in vitro culture condition, culture time, and blastocyst-stage transfer.’
What is Thoracopagus?
Thoracopagus describes conjoined twins who are joined at the upper chest. Often, cardiac function is affected too with the babies sharing one heart, or one malformed heart. Sometimes, as described in the case report, the babies have two hearts in a single pericardium (heart sack). Separation operations usually kill the babies but there are reports of successful separation operations, so termination is not the only option for women carrying conjoined twins, as some do survive. This type of conjoined twins is the most common at around 35% of cases.
Types of Conjoined Twins
There are many other types of conjoined twins. These are:
- Omphalopagus twins (joined at the abdomen – separation is usually successful).
- Xiphopagus twins (joined at the sternum – this type is the easiest to separate).
- Ischiopagus twins (joined at the front pelvis and lower spine).
- Ischio-omphalopagus twins (a combination of xiphopagus and ischiopagus).
- Parapagus twins (joined side by side at the torso).
- Dicephalus twins (where they have their own separate head but share a body).
- Craniopagus twins (joined at the head with separate necks and bodies).
- Cephalopagus twins (joined at the neck and head. Unfortunately these twins are brain damaged and are usually stillborn and the ones that aren’t only live a few hours).
- Cephalothoracopagus twins (joined at the head, neck and chest but with separate arms and legs. These share a malformed brain and are also stillborn or die shortly after birth).
- Diprosopus twins (this is where there are two faces on one head. The medical profession are unsure whether they are conjoined twins or a single, malformed baby).
- Pygopagus twins (joined back to back at the pelvis).
- Rachipagus twins (joined back to back at the spine).
- Parasitic Twin (this is where a partially formed twin is attached, usually just arms or legs or part of a body that is kept alive by the other twin’s circulatory system. It cannot sustain life on its own and should be removed as it will continue to grow and put a strain on the other twin’s heart.
For more information on conjoined twins, see: http://www.umm.edu/conjoined_twins/facts.htm
Sources:
- General Info on Conjoined Twins, page accessed 4th July 2011.
- Conjoined twins after intracytoplasmic sperm injection and transfer of day-3 embryos, Fertility and Sterility, 1st July 2011
- Successful Separation of Thoracopagus Conjoined Twins with a Single Extra-hepatic Biliary System, Case Report, J Med Assoc Thai Vol. 90 No. 5 2007.
Joanna Karpasea-Jones - I have been a health writer since 1997 when I published my own newsletter, SHOTS. I have written 2 books on childhood health, and write ...
