Monoamniotic Twins

There are two types of twins: fraternal and identical.

Fraternal twins are created when two separate eggs are fertilized by two separate sperm. As these twins are the result of two separate fertilisations, they can look very different when born. Like any two siblings, it’s reported fraternal twins share 50% of their genes.

When one egg is fertilised by one sperm, and the single egg then splits creating two separate embryos. These embryos have the exact same genes, resulting in identical twins. Identical twins are always the same sex, as they share 100% of their genes.

The timing of the egg split is the main factor in the result of Momo twins. At conception, one of the first things to form is the yolk sac. Then placenta and chorionic sac begin to form probably around the same time.

Next to form is the amniotic sac. If the egg splits before the placenta has formed, (day 1-3 of fertilisation) each embryo will have their own placenta, chorionic sac, and amniotic sac. If the egg splits after the placenta has formed (day 4-8 of fertilisation), then the two embryos will share a placenta and chorion, but will have their very own amniotic sac. But if they split after the amniotic sac has begun to form (estimates range between 8 to 12 days after fertilisation), then both babies will have to share an amniotic sac. Should the split take place any later than day 12, this will result in conjoined twins. Why the egg splits or the timing of the egg splitting remains a mystery.

Monoamniotic Twins are the result of the egg splitting after the placenta and amniotic sac have formed, resulting in the embryos sharing both. This immediately creates dangers due to the fact the babies, as they grow, will have skin to skin contact, can become entangled in each other's cords or at a later stage, compress the cords resulting in foetal death. However with the right care and treatment, you can avoid this horrible outcome and go on to have both babies successfully. They will most definitely be pre-term.

Cord 'accidents' are the number one risks in Momo pregnancies. It is very likely for the majority of cord entanglement to occur within the first trimester of the pregnancy, however this does not necessarily mean the babies will die, there has to be cord compression for this to occur. However most cord 'accidents' are gradual, so symptoms can be detected via high resolution ultrasound and/or fetal monitoring. This is where you come in. You need to tell your consultant from the start you want constant monitoring of your babies growth and of their cords.

There is no treatment for this type of pregnancy, there is no magic potion you can take to make it all better. However, early delivery is a must to ensure the babies are safe. If problems are discovered before viability, usually 24 weeks, there is nothing doctors can do. However after 24 weeks, babies can be delivered and receive treatment in NICU. There are still plenty of risks when babies are born that early, preterm birth is also a scary time for both babies and parents. Around 24 weeks you should request steroid injections to help develop the babies lungs. With normal pregnancies, the longer the babies are in the womb the better their development, however with Momo twins, the risks increase dramatically as the pregnancy progresses and due to fatal cord 'accidents'.

Delivery should be considered between 32 and 36 weeks. Any later than 36 weeks and, as studies have proven, the risks of fetal death are dramatically increased. A c-section delivery is a must, under no circumstances should a natural delivery be attempted.

There is still hope however as a separating membrane, or hairline membrane, can be found via high resolution ultra sound up to 18 weeks. In some cases, a membrane hasn't been found until delivery. However, if upon ultra sound scans cord entanglement is detected, then you can be sure the babies are in the same sac. A lot of Momo pregnancies are misdiagnosed, so there is always a chance your babies are in separate sacs.

Finally, be happy with the consultant you have in the hospital. You will be spending a lot of time with them, you will need to feel comfortable with them, and feel they want to give you the best possible care to ensure successful and safe delivery of your babies. If you are not happy, don't hesitate to change. Be confident they have experience and knowledge of Momo pregnancies. A lot of consultants will have heard of this type of pregnancy but not necessarily experienced one.

Some useful points to discuss with your consultant:

1. Discuss treatment - request regular scanning and traces from about 20 weeks.

2. Ensure you are scanned at least twice a week after 22 weeks.

3. Ask where the hospital stand on going 'in-patient'. This would be recommended from 28 weeks. Staying in the hospital 24 hours a day, with regular scanning and cord monitoring, ensures problems are detected sooner rather than later.

4. Request steroid injections between 23 and 26 weeks, to help develop your babies lungs.

5. Ask to visit the NICU and SCBU. Your babies will have to spend there once they are born, and it's best to see it and be prepared.

6. Discuss TTTS (Twin to Twin Syndrome) with your consultant, as they will be monitoring your babies size and growth closely.

7. ASK ASK ASK - never be afraid to ASK - you are the advocate for your babies!!

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