Chorionicity in Twins: Ultrasound & Stories from Twin Moms

Finding out chorionicity in twins is extremely important. Even though much progress has occurred during the past decades, some women are still misdiagnosed or are not being told about the importance of correct determination of chorionicity. Chorionicity in twins is determined through ultrasound and relates to the number of placentas. Your twins can share a placenta or each have a placenta. Monochorionic twins share a placenta and are always identical. Dichorionic twins have a placenta each. They can be fraternal or identical twins. About 1/3 of identical twins are dichorionic twins, fraternal twins are always dichorionic.

How will I know what I’m expecting?

You need to get a chorionicity scan in order to know whether you’re expecting monochorionic or dichorionic twins. It’s usually done at the same time as your dating scan between 11 and 13+6 weeks. It might be done sooner if you’re in fertility treatment or you get an early scan. It’s extremely important that you get a chorionicity scan as monochorionic twins need to be monitored more than dichorionic twins. That’s because monochorionic twins are more at risk of pregnancy complications such as Twin to Twin Transfusion Syndrome and Selective Intrauterine Growth Restriction (sIUGR).



Misdiagnosis of Chorionicity: Lyndsey’s story

Mom: Lyndsey Vigil – misdiagnosis of chorionicity, from mo-mo, to di-di to mo-di twins.

chorionicity in twinsTwin girls 3D

What were you told about chorionicity?
“At first I was told mo-mo twins because they shared a placenta and they couldn’t see a dividing membrane. At 8 weeks they changed it to di-di twins. I did my own research on shared placenta twins with their own amniotic sacs and came across mo-di twins. I called the doctor’s office and told them what I had discovered on my own – with the help of the modi/momo pregnancy group on Facebook as well as the multiples support group on Facebook. It was the next appointment after that they too confirmed mo-di, after I told them.”

Have you been happy with the care you’ve received?
“Unfortunately my care with my MFM specialist has not been very good for the first half of my pregnancy. At around 14 weeks the MFM technician let the MFM doctor know that one of my babies has a SUA.* The doctor told the technician “it’s too early to see that.” And again at around 16 weeks she told him about the SUA. He came and scanned me himself and said “well, I think I see two vessels.” I think. Which really bothered me. I let my OB office know I was not happy with the care and uncertainty from the MFM’s office. Unfortunately my state has low resources when it comes to finding a traveling MFM specialist.”

*Occasionally, there is only one single umbilical artery (SUA) present in the umbilical cord – this is opposed to the normal two.

What steps did you take?
“I attempted to seek out other OB offices in towns around my own about 1-2 hours away. Unfortunately they all use the same MFM specialist. I’d literally have to travel 5+ hours to physically be seen by a different specialist every two weeks for care. That is difficult when you have other children and finances that need attention. My OB office saw me that next week, after I told them about what the MFM technician said versus what the MFM doctor was saying leaving me in confusion and anxiety. I was seen in my OB office at 17 weeks, and they confirmed that my baby B had the SUA.”

What happened then?
“At 18 weeks along I told the MFM specialist that I had asked my OB office to take a look and confirmed the SUA. My OB doctor told me he wanted his office to scan me every two weeks to check on baby B’s growth. As of 18 weeks pregnant I have been seen two times a month by the MFM specialist and two times a month by the OB’s office. My care so fare after 18 weeks has been more at ease, but I’m only half way through this pregnancy. At my last scan at my 22 week appointment the discordance between the babies is at 15 percent. My babies are in the 10th percentile. I haven’t heard from the MFM specialist regarding Intrauterine Growth Restriction (IUGR). It makes me anxious, and I wonder if he knows what that even is coming from a low resourced state.”


Chorionicity in Twins: Lisa’s story

Mom: Lisa Kettrick – misdiagnosis of chorionicity, diagnosed with stage 3 TTTS.

chorionicity in twins

When did you learn about your twins chorionicity?
“I got told by the OB at 12 weeks that I had di-di twins, but she said she wasn’t a specialist, so she referred me on to the MFM specialist. At 15+5 weeks I had my appointment with him where he sent me for a scan – again with an OB! I don’t know if the MFM specialist even reviewed the scans, as I feel he just took for granted what the OB had said, as he asked me what type of twins they were! Two days later I went for a private scan to find out the genders as the OB said that the NHS won’t disclose this that early – although same gender twins can also be a hint of mo-di twins. At the private scan clinic the sonographer told me that she thought that my twins were mo-di twins.”

When did you have your next appointment?
“Our next NHS scan was at 20+6 weeks. Our OB referred us to the on duty MFM specialist – we were then found to have stage 3 TTTS! The next day I was sent to Birmingham to see the top professor who admitted me and operated on me the following morning. He did laser ablation and drained nearly three liters of fluid from around one baby! We were so lucky to have been found in time and then treated so quickly.”

How are your boys doing at this point in time?
“I’m at 26 weeks, a couple of weeks on from the surgery, and the boys are doing well so far. I’ve had a check up scan, and the boys have had a MRI scan to check their brain functions. Our surgeon contacts our local MFM specialist on the day of our scans because he likes to follow our progress and check that we are receiving all of the required tests/care. His name is Mark Kilby, and we think he is amazing!! I feel very disgruntled by the first ‘specialist,’ but I must state that since the 20 week scan, I couldn’t have received any better care from the NHS. Apart from that first Doctor, I’ve found every person I’ve come across to be amazing.”


Chorionicity in Twins: Lindsey’s story

Mom: Lindsey Lowrance – misdiagnosis of chorionicity, thought her babies were di-di twins until birth.

chorionicity in twins

When did you find out that you were pregnant with twins, and when did you learn about your twins chorionicity?
“At 8 weeks I found out that I was pregnant and that it was twins. This was after they told me I was not pregnant the first month and insisted I only had ovarian cysts, so I returned a month later expecting to talk about removing the cysts only to find I was in fact pregnant. At 10 weeks the OB told me it was di-di twins and said the same again at 12 weeks.”

How did you find out that you were misdiagnosed?
I did not know that my twins were mo-di until delivering the placenta. This was when my OB saw two connecting vessels, and my twins were then diagnosed with TTTS and sIUGR. Luckily I had convinced my OB to induce me at 37 weeks instead of waiting until 38. I felt the babies needed to come out, and I had almost two weeks of intense false labor. My baby A was born at 5lbs, 7oz (2466 grams) and baby B was born at 3lbs, 12oz (1700 grams). It wasn’t until weeks later that I was trying to make sense of what happened and my OB telling me how extremely rare and unique the situation was that I reached out to a group of mo-di moms and shared my early ultrasound pictures. All of the moms knew right away that it was mo-di… But my OB hadn’t.”

Would you do anything differently if you could go back in time? What’s your best advice to parents in a similar situation?
“My OB never mentioned anything about seeing a MFM specialist. He told me a couple of times that he would have had me go that route if I had mo-di or mo-mo twins because of the higher risk, but insisted that I was in good hands with him for di-di twins. I had also asked him around 20 weeks about whether I should see a MFM specialist and he became offended. If I could change anything, I wish I had gotten an expert opinion and had more than one doctor involved to ensure the safety of the babies and pregnancy. I’ve since learned that all twin pregnancies should see a MFM specialist. I wish my OB had practiced this advice and that I had more knowledge to advocate for myself and babies. I wish I didn’t blindly trust my OB.”


Chorionicity in Twins: Nicole’s story

Mom: Nicole Weiershauser – had to fight hard to get determination of chorionicity in due time

chorionicity in twinschorionicity in twins

When did you find out that you were pregnant with twins?
“I found out I was pregnant with twins on November 27, 2017. The ultrasound showed I was around 8 weeks pregnant. At that initial appointment, my OB said he couldn’t tell if they were identical or fraternal. I didn’t think much of it at that point because I knew nothing about twin pregnancies.”

When did you learn about your twins chorionicity?
“A few weeks after that appointment I sought support through a twins Facebook group. Through reading people’s posts, I discovered that basically everyone knew if their twins were identical or not. I also learned about chorionicity and terms like mo-di, mo-mo and di-di. It was the first time I’d heard these terms. My OB never used them. I was shocked that I was told so little about my twin pregnancy. I quickly learned how risky monochorionic pregnancies are. I was now frantic to learn if my babies where sharing a placenta. My “mother intuition” told me they were and therefore identical. I felt desperate for opinions so I posted my 8 week ultrasound on the twins Facebook group. Within minutes, I had over 100 people telling me my twins were modi and to get a MFM specialist referral. I didn’t want to wait to get that referral so I called my OB that day, it was a Friday.”

What happened next?
“My conversation did not go as planned. What I thought would be an easy referral was not. I could tell right away he didn’t want to give me one. I kept our conversation to the point, I told him, “I am 37 years old and pregnant with twins. I want to know if they are identical so I can be more closely monitored.” He told me to trust him and that he could handle the pregnancy. When I mentioned the risk of TTTS he said nothing could be done until after 20 weeks anyway. He said I was worrying too much and I should just “sit tight” for a few weeks until my 20 week anatomy scan. He said I shouldn’t be concerned since we don’t even know if they are the same gender yet. He ended our conversation by saying that if they are the same gender, we can talk about a MFM specialist referral then.”

How did you react?
“When I hung up the phone, I immediately told my Facebook group how our conversation went. The members and even administrators told me how wrong and uninformed my OB was and that I should find a new OB and get a MFM specialist referral. I told my family and husband that I thought my twins are mo-di, and I need to find out ASAP so I can be monitored correctly. They told me to trust my doctor and not let random people on Facebook tell me about my pregnancy. They thought I was crazy to post my ultrasound online and trust strangers on the internet. It even sounded a bit crazy to me, so I spent all weekend doing my own research on twins and studying every twin ultrasound I could find. All my research confirmed that they were mo-di twins. I decided I didn’t want to go back to my OB since he treated me poorly and dismissed my concerns. I called a bunch of new doctors. Unfortunately, I was told it would take weeks to get a new patient appointment. I had no other choice than to call my old OB and demand a referral to a MFM specialist.”

How did your conversation go?
“On Monday I called my OB. It was a conversation that still makes my blood boil. The second he answered the phone I could tell by his tone that he was annoyed. I told him I wasn’t able to sleep all weekend because I needed to know my twin type. If he couldn’t tell me, we should treat it as if it were a monochorionic pregnancy, and he should refer me. He asked me why I thought they were identical. I reluctantly told him I researched ultrasounds on the internet and received guidance from a twin pregnancy group. I explained that my ultrasound shows one black chorion with two babies in it. He acted as if he didn’t understand, so I said that the big black “blob” on my ultrasound has two babies in it. My answer infuriated him and he shouted, “Where did you get your MD?” Then he yelled, “Even if I give you that referral there is nothing anyone can do for you!” I remained super calm as he went on his tangent. I lied and I quietly reassured him that it was nothing against him, and that I needed that referral for my “own anxiety.” After what seemed like hours of being belittled he finally agreed. I apologized for questioning him and gave him the name of the MFM specialist I wanted to be referred to. Then he said he’d have his scheduler make the appointment and get back to me. When the scheduler got back to me, she said that the MFM doesn’t want to see me until I’m at least 20 weeks into my pregnancy. She said, that my OB and I can discuss this more at my 20 week anatomy scan like he originally wanted.”

How did that make you feel?
“I felt so defeated and incredibly angry. As soon as I was done crying, I picked up the phone and called the MFM specialist office directly. I gave her my name and asked her if it was true that they wouldn’t see a 37 year old who’s pregnant with twins until at least 20 weeks. She said no, that information is not true. She looked up my name in her computer and there was no record of me or a referral. She told me that as soon as she gets a referral for me, I can see a MFM doctor. I called my OB’s scheduler and told her that when I called the MFM specialist, they were willing to see me ASAP. I asked her to fax my referral immediately. I also told her I would be scheduling my own appointment with them. A couple of days later my referral went through, and I was able to schedule my own MFM appointment.”

What happened at that appointment?
“On January 30, 2018, I had my first MFM appointment, and she said that my pregnancy was indeed a monochorionic diamniotic pregnancy. Facebook moms had been correct! I was finally going to get the care and monitoring I needed. The MFM specialist directed me to a new OB, and I never had to deal with my old OB again. At 36 weeks, on June 11, 2018, I delivered two healthy baby boys.”

What’s your best advice to parents in a similar situation?
“If it weren’t for that Facebook group, I would have never known about different twin types or the importance of seeing a maternal fetal medicine specialist. I was extremely lucky to have had a perfect, complication free pregnancy. I’m extremely concerned to know what happens to the moms and twin babies who solely rely on an uninformed OB. OBs need to become aware of how important it is to know twin chorionicity. I think it should be mandatory for all twin pregnancies to see a MFM specialist at 16 weeks. My best advice to parents is to learn as much as you can about twin pregnancies, read books, join Facebook groups and/or research online. Don’t be afraid to question your doctor and trust your own instincts. If your doctor is unable to answer your questions find a new one. Remember, no one is going to advocate for your babies care as much as you are. Never give up!”

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2 Responses

  1. Nicole Weiershauser says:

    Hi Jimena,

    Hope you and your boys are doing well! It is definitely mind blowing how uninformed OBs are at reading twin ultrasounds. I am still planning on writing the medical board and letting them know how poorly I was treated. Us moms need to keep on channeling our mama bear instincts and fight for our babies! Good luck in Mexico!!


  2. Jimena says:

    I’m really glad everything ended well for you despite the way you were treated at the beginning of your pregnancy. My blood was boiling too over the mistreatment and manipulation you received from your OB and his scheduler. They basically schemed a plot to shut you up and have you quiet! This is very wrong….
    Also, as far as I know, not only the sooner you know your chorionicity the better for the sake of the pregnancy but also I’ve been told it’s much easier to determine it early than later on. It’s much more difficult to see later on week 20!
    In my case (mo/di twins, also boys 😉 my OB has no idea either. He told me at 9 weeks it looked like fraternal when I see clearly now knowing a little they were mo/di. Also he said nothing about the placentas he only said this because I had to yolk sacs at the moment. I also faught hard to determine what I had. And to get the medical tests I need since we moved to Mexico and here no one has asked me to get blood analysis, and many other medical test I have to fight for…
    Congratulations on your twins and you are right, we are the better advocates for our babies no doubt about that!!