Twins are a serious concern. There is a general lack of information and knowledge about them. They are not good or exciting. The only twins that I imagine to be good are those that are at least five years old, healthy and attending school. Finally a break for the parents. Twins are a lot of work. Unfortunately, it has become more frequent to see twins, and there are being posted all over the internet. It is concerning about the lack of understanding about the serious and life threatening risks that twins face. They are lucky (in some cases) just to make it through pregnancy and survive.
Take for example a recent picture posted on Facebook. I won’t show it here, but this is a link to it (I hate to admit that I visited this page, but it is a good place for a laugh or just to let of steam yelling at the screen). The argument is this: twin A is pale because of early cord clamping and twin B is darker because of delayed cord clamping. I call it a bunch of people talking about something about which they have very little knowledge or information. In the discussion, they clearly mention that this was a “mono” pregnancy, but then seem confused what this means. If you don’t know the different types of twins, for bloody sakes, DON’T GIVE OUT MEDICAL INFORMATION about TWINS!!
Here is my twin primer.
Zygosity – refers to the number of eggs involved in the conception
Monozygotic – one egg fertilized, and then split into twins. These are “identical twins“. They are the same sex.
Dizygotic – two egg fertilized, two fetuses develop. These are “fraternal twins“. They can be the same or different sexes.
Simple so far? Most twins are dizygotic, and this is especially so if the pregnancy results from infertility drugs. In Canada, about 2/3 of twins are dizygotic.
Chorionicity – refers to the number of chorion (for easy remembering, this is the outer sac and placenta).
Dichorionic – Two chorions. All dizygotic pregnancies (two fertilized eggs) results in dichorionic pregnancies. Because there are two placentas and two outer sacs, there must also be two inner sacs (amniotic sac) so these pregnancies are also diamniotic. Now where this starts to get complicated is sometimes the two embryos implant very close to each other. Their placentas may touch or even be called fused. This just refers to what can be seen on ultrasound; the placentas are not actually fused, there is no shared placenta or blood volume, and when delivered, it is not difficult to separate the two placentas. Identical twins, if the sepearation of the one egg occurs before three days, two distinct embryos will develop, each with their own placenta. Although they are identical, they do not share a placenta or blood.
Monochorionic – These MUST be identical twins, but not all identical twins are monochorionic. These are twins that separated from a single egg between days 3-8 after conception. They represent 2/3 of identical twins. The separation occurs after the cells that are destined to be the placenta have developed separately from the embyro(s). This means they share a placenta. If they share a placenta, they share the blood vessels associated with the placenta, and therefore are likely to share their blood volumes. These are more complicated twins and anyone who says otherwise has absolutely no clue what they are talking about. Think about this way, these twins are conjoined at the placenta!! These twins have only one external sac, and are further classified as to the number of internal sacs (amnions).
Monochorionic-Diamniotic – These twins share a placenta, but each have their own internal sac. There are essential only two thin membranes between the twins (the amnion for each twin). They are joined at the placenta, and almost universally share their blood volumes. However, babies are not known for their sharing skills! Due to the organization of blood vessels in the shared placenta, it is possible to have an unequal distribution of fluid (blood) and/or nutrients. Twin-Twin transfusion syndrome (TTTS) is a condition whereby one twin (the donor) is slowly and consistently given its blood volume to the other twin (the recipient). This occurs in 15% of mono-di twins. If they don’t share equal portions of the placenta, they will not receive equal nutrition from the mother. This can lead to one of the babies becoming severely growth restricted. This also occurs in 15% of mono-di pregnancies. Even more complicated is when both situations occur at the same time, generally not a good outcome for one or both twins. These conditions can only be reliably identified with ultrasound and routine screening for these pregnancies will improve outcomes (there are some treatment options). I promise a future post just about TTTS, I owe it to a friend who lost a baby to this condition.
Monochorionic-monoamniotic – These twins not only share a placenta but share a sac. These twins separate later, but days 8-12. These are much more rare, accounting for 1% of monozygotic twins. This is a very dangerous situation, because they are at risk for all of the other complications with a shared placenta, plus they can tangle their cords and make knots. This is risky because it can cause one or both twins to die. The most risky time for these twins is labour. They are all delivered by elective c-section at 32-34 weeks.
There are other more rare conditions, which as a perinatologist, find very interesting. However, I would be happy if health care providers and the so-call child birth educators could just get these basics right. Twins aren’t good, shared placentas are worse.
Back to the picture in discussion. Do I really think this difference is cause by delayed cord clamping of only one baby?? Absolutely not. This is a pathological image where one baby is clearly anemic (low red blood cells) and the other is polycythemic (too many red blood cells). This did not happen at delivery, these babies would have looked exactly the same if delivered by c-section and both cords clamped at the same time. Reading the site where the picture was posted, they even comment on the fact that the darker twin needed more help. This isn’t surprising to someone who routinely cares for complicated twins. Generally, the smaller anemic twin is more fiesty than the bigger polycythemic twin. The little twin has been fighting to get its fair share, perhaps a little stressed and ready to get out of there. The bigger twin just got everything given to it, had a cushy environment and is generally not ready to be delivered. Sudden it has to work to survive – this is why they often need help. Plus they have extra red blood cells to break down, so they are also at risk for jaundice.
If only twin B had delivered first and had early cord clamping and then twin A second with delayed clamping. That would have fixed everything, right?? If we are suppose to trust birth, why didn’t these babies just come out in the right order?