Positive partial Monosomy 13 NIPT result

I had my draw for NIPT testing done on 2/13 at 11w through Myriad, and received my results on 3/3. The morning of the day I received my results, I got an email from Myriad notifying me that my sample had been re-run on 2/23, and I could expect results soon (ended up getting results around 1:30 pm).

When my fiance and I opened them, there was instantly a flag for monosomy 13. We were so confused at first, as NIPT tests for trisomies and fetal sex, so I had no idea what a monosomy was. Further into the report in the “additional findings” section, it said “Assay results are consistent with a partial deletion of chromosome 13. This finding may reflect chromosomal status of the fetus, placenta, and/or the patient, or it may be a false positive. Chromosomal studies and genetic counseling are recommended.”

Obviously we instantly freaked out. We started googling and found that this is incredibly rare, and there have been many reports of false positives for monosomy 13 specifically. We actually had an elective ultrasound at a women’s center on 2/28, where I was 13w on the dot. Baby looked completely “normal”. Head and all limbs measured exactly on track, facial midline is established. Eye formation, nose, and chin formation are all clearly visible. Abdomen appears to be closed, and heart rate was 164 bpm. Every appointment and ultrasound I’ve had have been indicative of a completely healthy pregnancy.

My midwife reached out to me shortly after the results released and let me know she is referring me to an MFM. From what I’ve read, they’ll do more in-depth ultrasounds, genetic counseling, and further testing if that’s what we would like to do. She said I should hear from them by 3/10 and I’ll be able to schedule an appointment when they call.

I’ve talked myself off a ledge a little bit, as I now know that Confined Placental Mosaicism is most commonly the reason for these positive results, but the thought of microdeletions absolutely terrifies me. This is my first pregnancy, so all of this is 100% new to me and my fiance. I’d like to add that my fetal fraction was 20.5% (tall and thin with low BMI), so Myriad had plenty of DNA to work with.

I know I’m going to be in complete limbo until my MFM appointment, which is truly the hardest part. Just looking for some advice or experience with an experience like this. I know that I’ll talk more with my MFM about amniocentesis as well, but if anyone has experience with this testing they could share I’d really appreciate it. I’d like to be as prepared as possible for any outcome.