Yesterday (3/27/23) was an amazing day. We went to the new doctor's office for a second opinion and additional scan. When the new ultrasound was conducted, they were able to locate both of their nasal bones--which had been missing on the previous ultrasound. This was a major relief, and a somewhat unexpected one. When we had the doctor's appointment last week, the lack of nasal bones and high NT reading had them very concerned. And I understand why. When conducting my desk research, I came across multiple articles linking the absence of nasal bones during the 11-14 week ultrasound and trisomy 21. In fact, this NIH study found that the nasal bone was absent in only 0.5% of chromosomally normal fetuses (3 out of 603 observations) during ultrasounds at 11-14 weeks gestation. Which had us very concerned. Given the odds, it was an amazing discover that the new scan showed that these had formed later...or perhaps they were just able to get a better view. Either way, I'm happy we went for this second opinion.
Additionally, the new doctor said that the NT reading for baby A was the same as last week (1.5), but baby B was now 1.7, which is a far cry from the 2.8 reading we had last week. As noted in a previous blog post, several articles claim that the normal NT range is upward of about 3.0 mm. However, this does not tell the full picture--it is not just the NT score, but the NT as a percentage of the baby's size. Baby B is smaller than A and smaller than average, so an NT of 2.8 put B in the top 95th percentile for B's size.
I am not sure why the NT changed so much--is it because B grew more in a week, or because of an inaccurate scan/measurement? This is something I will have to investigate further. But it did have me wondering--if it was an inaccurate scan/measurement...which one was off? The first one, or this new one? I pondered that for a few hours yesterday until we received a call from the first doctor's office. They had our blood test results and it had only been a week (was supposed to be two weeks). The results came back negative for Trisomy 13, 18, and 21--there is only a 1 in 10,000 chance that they will have one of these conditions.
This was a major relief and massive U-turn from last week. I understand why the doctors were so negative last week--the absence of nasal bones and high NT at this stage of the pregnancy was not good, so they let us know that their outlook wasn't positive. We were devastated, but only to find out a week later that things are looking much better. I get that it is a science and they are running off the odds--as a social scientist I deal with data and probabilities every day, so I understand this better than most--but it certainly put us in a tough position mentally. Talk about a rollercoaster ride of emotions.
Although we received this (very) positive and unexpected news, we are still in for a long few months. The biggest and most likely hurdle we now need to overcome is potential twin-twin transfusion syndrome (TTTS). According to the doctor, this occurs in 15% of mono di pregnancies, and is most likely to occur during the 16 - 28 week period. There are also factors that can increase these odds, and the first doctor mentioned the egg splitting later than "normal" is one of those--which they somehow can tell occurred (don't ask me how). Which places us north of the 15% average. Therefore, beginning at the 16 week mark, there will need to be weekly ultrasounds to monitor how they are developing and if TTTS is likely. So, fingers crossed we can make it through that, but for now we are celebrating this major victory. We will cross the next bridge when we get there. Right now I am just taking this one day at a time.