• Question: how would you get conjoined twins

    Asked by rare493tet on 15 Nov 2023.
    • Photo: Michael Schubert

      Michael Schubert answered on 15 Nov 2023:

      Very early in an embryo’s development, it may try to separate and develop into two individuals (who would be identical twins if this happened correctly). It’s very rare, but sometimes, that process goes wrong and the embryo doesn’t fully separate. The result is that two individuals develop, but stay physically connected in some way, so that they share some parts of their bodies.

      Some common ways conjoined twins are connected is at the chest (which means that they may share organs in or below the chest), abdomen (which means that they may share organs in their midsection or parts below it), or pelvis (which means that they may share their lower abdominal organs or body parts such as legs).

      Because we have learnt a lot about medicine, surgery, and health technology, many conjoined twins can now be separated. Some can’t, though, if they are too connected for the procedure to be safe or if they share a body part that we can’t easily divide or replace. Even if they share a lot of body parts, conjoined twins are still two individual people with their own thoughts, feelings, and preferences.

    • Photo: Sophie Shaw

      Sophie Shaw answered on 16 Nov 2023:

      Michael has explained this brilliantly! It’s where embryos don’t separate properly during development.

    • Photo: Caroline Hyde

      Caroline Hyde answered on 17 Nov 2023:

      Michael has explained this really well already. Basically, it has to do with the fact that in the early stages of development, the embryonic cells grow by dividing into 2. This is a hugely complex process and in the end, an embryo can only fully develop if all the correct progenitor cells are in the right place so to speak. So if very unfortunately, the cells responsible for an area/organ that remains joined in conjoined cells haven’t separated correctly at the right time, then they end up producing a single shared area/organ, rather than 2 separate parts of the twins’ bodies.

    • Photo: Martin Minarik

      Martin Minarik answered on 18 Nov 2023:

      There is also a special case called chimerism, when a mother is pregnant with non-identical twins, but when they’re still early embryos, one of them absorbs the other one and they then grow into a single person, but with a mixture of DNA from two people. There was this famous case in the US where a father asked for a paternity test, and the results showed he is the father, but his wife wasn’t the mother. It turned out when she was an embryo, she absorbed her sister, and some of her organs were made by her sister’s cells, including her ovaries. So her children were genetically in fact her nieces/nephews after her unborn sister. There are even cases of people with female/male chimerism…I admit, I’m a bit obsessed about this as it happens a lot with the fish I study 😀