Can you have identical twins in different placentas?
Identical twins may either have their own separate placentas or they may share a common placenta. The impetus for and the timing of the embryo to split into identical twins is unknown, but the later this occurs the more complications are seen.
In the uterus, a majority of monozygotic twins (60–70%) share the same placenta but have separate amniotic sacs. A small number (1–2%) of monozygotic twins share the same placenta and amniotic sac. Fraternal twins each have their own placenta and own amniotic sac.
- The likelihood of you having identical twins is about one in 350 to 400 . About a third of twins are identical . Whether or not you conceive identical twins seems to be entirely down to chance. Identical twins develop when one fertilised egg divides into two.
- So whatever is true for brothers and sisters, is true for fraternal twins too. And since brothers and sisters can have different blood types, so too can fraternal twins. It is a different story if the twins are identical. Identical twins come from the same egg and the same sperm and so share nearly identical DNA.
- So identical twins come from one zygote that splits into two embryos. Fraternal twins, on the other hand, are called "dizygotic." This means they start out from two different zygotes, which means they come from two different eggs, each fertilized by a sperm.
This is early enough for the separate membranes and placentas to grow from the egg sac. So, DCDA twins can be identical or non-identical. Both babies share one placenta and one outer membrane, but they each have their own separate, inner membrane .
- Monoamniotic twins are identical twins that share the same amniotic sac within their mother's uterus. Monoamniotic twins are always identical, always monochorionic and are usually termed Monoamniotic-Monochorionic ("MoMo" or "Mono Mono") twins. They also share the placenta, but have two separate umbilical cords.
- In some cases, a delayed interval birth takes place when one multiple is delivered prematurely, but doctors are able to halt labor and keep the remaining multiple(s) in their mother's womb to grow and develop. Some of these multiples—twins, triplets or more—were born days, weeks or even months apart.
- Monozygotic twins are called "identical" because they often have remarkably similar appearances and characteristics, which stem from the fact that they have identical DNA. Fraternal twins, on the other hand, are as alike as any two siblings. They may look very different.
Monoamniotic twins are identical twins that share the same amniotic sac within their mother's uterus. Monoamniotic twins are always identical, always monochorionic and are usually termed Monoamniotic-Monochorionic ("MoMo" or "Mono Mono") twins. They also share the placenta, but have two separate umbilical cords.
- Monozygotic twins are genetically identical unless there has been a mutation in development. and they are almost always the same gender. (On extremely rare occasions. an original XXY zygote may form monozygotic boy/girl twins by dropping the Y chromosome for one twin and the extra X chromosome for the other.)
- Yes, it can happen. In fact, one study estimates that as many as 1 in 400 sets of fraternal twins is "bipaternal." How is it possible? Simple: Two eggs from the same mother get fertilized by two different fathers – within the same ovulation period.
- Identical twins often share the same placenta, usually have separate amniotic sacs, and always have their own umbilical cords. Non identical twins have separate placentas, amniotic sacs, and umbilical cords.
Updated: 2nd October 2019