Low hCG and PAPP-A in a Patient with an Autoimmune Disorder
Hi! I just got my 1st trimester screening test results today, and would love you thoughts.
I will be 40 years old when I deliver. I was 12 weeks when I did the testing.
Nasal Bone present
Free b - HCG: 0.29 MoM
Papp A - 0.34 MoM
Down syndrome risk: 1:1600
Trisomy 18 & 13: 1:50 (normal for my age 1:150)
I have an autoimmune condition, polymyositis that is under control. I am taking 12.5mg prednisone 1xday. I am ANA and Jo-1 positive.
Can you please help me understand these results? I am trying to look at the fact that it is only a 2% chance of the trisomy abnormalities, but it is difficult.
Are there any other reasons that my blood levels would be so low for both? Is there anything I should be precautionary about through the rest of my pregnancy because of this?
The combination of the low hCG and the low PAPP-A is typically a pattern seen in pregnancies complicated by trisomies 18 and 13 (in contrast to an elevated hCG coupled with a low PAPP-A in Down syndrome – trisomy 21). Both hCG and PAPP-A are produced by the trophoblasts of the placenta and low values could be the result of either a small placental mass or decreased production because of metabolic dysfunction. Both of these factors might be at work in trisomies 18 and 13.
However, in your case, there is also the possibility that your baby is chromosomally normal but has an abnormality of placentation that resulted from your autoimmune disorder. The immune system probably plays a very important role in normal placentation and the presence of certain autoantibodies (e.g., antiphospholipid antibodies, lupus anticoagulants, and anti-beta-2-glycoprotein-1) are thought to be associated with increased risk for abnormalities of placentation resulting from abnormal trophoblast migration and invasion of the maternal spiral arterioles. Indeed, if you have not been screened for these specific autoantibodies, I would recommend that you have that done. Such pregnancies are at increased risk for poor fetal growth (intrauterine growth restriction), fetal loss, pregnancy-induced hypertensive disorders, and early delivery. If you have any of these other autoantibodies, you might also be at increased risk for thromboembolic complications as well.
Whenever we find a pregnancy that has low hCG and PAPP-A levels and a chromosomally normal baby, it is recommended that fetal growth be followed at serial intervals, Doppler flow studies (e.g., umbilical, uterine , and fetal middle cerebral arteries) be done to evaluate impaired placental perfusion from either the fetal or maternal side and evidence of fetal blood flow redistribution (preservation of the brain at the expense of perfusion of ‘nonessential’ organs because of reduced placental transfer), and both mother and baby be monitored carefully for evidence of compromise. Your doctors can give you specific details of what should be done with regard to the latter.
Best of luck to you and please let us know how things turn out.