Abnormal First Trimester Screen in a Woman with Chronic Kidney Disease
Tuesday, July 07, 2009
Kenneth F. Trofatter, Jr., MD, PhD
I am also new to the whole blogging thing. I am currently 13 weeks 3 days, and was told at my last prenatal appointment that based on my first trimester screening, I have a 1 in 235 chance of having a baby with Downs syndrome. I am only 23 years old, and I wasn't sure if this is horrible. I thought most people had a 1 in 275 chance, but looked it up online and came to find out that it’s more like 1 in 1200, so naturally was very concerned. I was wondering if you could shed some light on this whole odds thing, because I'm sort of freaking out. I do have kidney disease MPGN type 1 and Graves disease, not sure if that makes a difference. I have one other child he's 4 and very healthy, with no disabilities whatsoever. Hope you can help me understand this a bit more.
Thanks
To Leilani:
The risks for having a baby with Down syndrome and many other chromosomal abnormalities resulting from nondisjuntion increase with age with the actual risks also varying by pregnancy trimester. At your age your chance of delivering a baby with Down syndrome is only about 1 in 1250 and the chance of having a baby with any chromosomal abnormality only about 1 in 500. The first trimester chances that the baby could have a chromosomal abnormality are 20-30% greater than these because such babies have a higher chance of getting lost along the way. Your 1 in 235 risk based on the first trimester screening is equivalent to that of a 35 year old woman in first trimester. Hear me loud and clear, however, just because the risk screening result is therefore ‘abnormal’, that does NOT mean the baby necessarily has Down syndrome. Indeed, it has a 234 out of 235 chance (>99%) that it does not.
You did not tell me the actual results of your tests, but it is possible that your kidney disease skewed the risk assessment if you are not clearing the serum analytes (hCG and PAPP-A) normally, particularly the hCG. Indeed, if you have membranoproliferative glomerular nephritis (MPGN), that is often associated with decreased kidney function and about 20% of the pregnancy hormone hCG is typically excreted by the kidneys (that’s why you can do a pregnancy test on urine samples). If this led to a higher circulating hCG level, that might increase your 'risk' for Down syndrome but not the chance the baby actually has it.
If on the other hand (or in addition to), the PAPP-A level is on the low side, that might further increase your ‘risk’ for Down syndrome. Your kidney disease is an autoimmune condition in which your own antibodies attack the kidneys and cause activation of a series of chemicals called the complement system. Complement helps to further damage anything the antibodies attach to (and normally it is a very important means of fighting off organisms that cause infections). However, unlike hCG, PAPP-A clearance does NOT seem to be impaired in some patients with autoimmune kidney disease (Rysavá, et al., Kidney Blood Press Res 2007;30:1-7) and therefore your kidney disease might lead to an elevation of the hCG alone when compared to the PAPP-A levels. The greater the difference in the multiples of the median (MOMs) of those two pregnancy products, the greater your calculated ‘risk’ for Down syndrome.
You should also be aware that women who have autoimmune diseases, particularly those that affect the kidneys, are also at greater risk for having an abnormal placenta – a small and/or a poorly vascularized placenta – that can eventually lead to poor fetal growth, hypertensive disorders of pregnancy (preeclampsia), and need for early delivery. This could further reduce your PAPP-A out of proportion to the hCG (which is also made by the placenta) and increase the Down’s risk even further.
It is true that young women can have babies with Down syndrome and indeed, about two-thirds of babies with chromosomal abnormalities are actually born to women at low risk based on age alone. However, in your case, I am betting on your risk being elevated because of your autoimmune kidney disease. My suggestion would be to 'lay low' for a bit and simply have a good genetic sonogram done at about 18 weeks. If that is normal, it will reduce your ‘risk’ by at least 50%. Of course, you always have the option to have an amniocentesis done at 15-16 weeks if you just have to know for sure as soon as possible. Best wishes and let us know how things turn out.
Dr T
Labels: Down syndrome, first trimester screening, nondisjunction
10 Comments:
At Fri Jul 31, 03:46:00 PM 2009,
Anonymous said…
HI! I am 37 years old and because of irregular periods did not know I was pregnant until 14.5 weeks. I was on the pill while the baby was conceived. I will be 38 at the timem of delivery and this is our 4th surprise baby. I missed the first trimester screen but the second one the quad screen came back positive for Down Syndrome with the risk of 1: 140. I had problems with the second screen with my third child (the risk was 1: 110) and at that time I did an amnio and was told the baby was fine. I am in turmoilt right now as what to do with the results for the 4th baby. I will go for my detailed u/S in 10 days but was told that besides soft markers for Down syndrome they can not exactly tell you whether the baby actually has Down Syndrome or not. Would it be advisable knowing that to have the amnio? I dont want to risk the life of my baby but we are not clear about what to do if it actually comes back with Down Syndrome. My husband says he would keep it and I am once again in turmoil. What should we do?
At Thu Aug 06, 12:53:00 PM 2009,
Nancy said…
hi dr. trofatter!
i first want to take a minute to say thank you so much for running this blog and taking the time to answer our questions. yours is by far the most informative site i have come across on this particular topic.
my information is as follows:
34 yo (will be 35 at time of delivery)
189 pounds
african american
screening done at 13w4d
NT(mm): 1.5
CRL(mm): 80
Free Beta hCG(ng/ml): 303.99
Free Beta hCG(MOM): 7.63
Percentile: 99.9
PAPP-A(mIU/ml): 3.21
PAPP-A(MOM): 1.82
Percentile: 80
Delta NT: -0.25 (not sure what this is/means)
there was a nasal bone present however the lab does not consider this when Down's reuslts are greater than 1 in 100.
my risks were as follows:
1/85 - Down's
1/10,000 - Trisomy 18/13
at the time of the u/s the doctor told us based on what he could see everything looked good (perfect was his exact word) and if he were to rely only on the u/s he would screen us "negative" based on what was seen, but that the bloodwork would complete the picture for us to give a more specific risk factor.
now my questions are as follows. i have one kidney that does not function at 100%. in fact i have a stent placed now which is what keeps my kidney working however at last nuclear medicine scan (april 2009) the function of the left kidney was pegged at 16% (right kidney is fine). is this reduced function of the left kidney enough to skew my hCG results so high? when they called to give me my results they indicated it was likely the high beta that was driving me into the riskier category.
additionally this was an IVF pregnancy so i have been monitored closely and have very specific dates. my initial betas were very high (499 at 17dpo and 1992 at 19dpo) and initially the speculation was that i might have had twins (we transfer 2 blasts on day 5). there was never any indication that the 2nd blast ever took. my first u/s was approximately 5w4d, only one sac/hb was ever detected but my beta continued to be high.
Lastly my ob/gyn recently discovered that i am hypothyroid, my TSH was only .03 (should be .4 - 4.5). i was screened in february 2009 and at that time my TSH was 1.27 so apparantly pregnancy has brought on this condition. i have an appointment with an endocrinologist tomorrow but i will likely end up on syntroid. i am curious if any of these factors can throw my hCG numbers so far out of whack?
we have already decided to do the amnio which will be on the 17th (i will be 16w0d) but i am trying to find any information i can on the topic in the mean time. thanks in advance for any information you can provide.
nancy
At Wed Sep 02, 08:48:00 AM 2009,
Juliana Tomingas said…
Dear Dr. Trofatter,
I would love your advice on whether or not risk factors are the same when one is pregnant with multiples.
I am 37 years old (will be 38 in December), have delivered 7 perfectly healthy children, and am currently 13 w 6 d pregnant with MZ twins. The babies appear to share a placenta, but reside in separate sacs.
We had what I believe is considered the "combination screen" performed at 11 w 6 d. The NT scan showed one baby at 2.66 and the other at .9 thickness. The Dr. informed us that the results were "normal". However, when our results came back from the whole screening, we were given odds of 1:32 for DS for both babies.
I'm wondering how it is that the odds can be exactly the same for each baby when they had different NT readings. Do they just assign them the same risk since they appear to be MZ?
Also, how can the risk factor be so high when the NT was "normal"? We will not undergo the amnio, due to the risk factor. Of course, I would love to know with certainty, but we will cherish our children no matter what and won't risk the pregnancy unduly.
I'm just looking for some reassurance one way or the other. I should also note that our screening was performed by a special lab that supposedly ONLY does multiples.
I look forward to your response, and thank you sincerely for your service.
Juliana
At Fri Sep 04, 10:47:00 AM 2009,
Kenneth F. Trofatter, Jr., MD, PhD said…
To Juliana: I was not aware of "special labs that did only multiples," so I have no idea how they calculated your results. At your due date, you will be 38 years old. Your risk for a singleton baby having Down syndrome in first trimester, based on age alone, is about 1 in 100. If the twins are truly monozygotic, the risk should still be 1 in 100 basedon age alone! I do not know if the lab used only the NT measurement from the baby which had the widest one, or if they included the serum analytes (hCG and PAPP-A) in your revised risk assessment. Ask the Genetic counselor who works with the laboratory how they cam up with your results. I wish you the best and please let us know what you find out!
Dr T
At Thu Sep 17, 11:10:00 AM 2009,
Nancy said…
hi again!
this is an update from nancy on 8/6/09 @ 12:53. i just wanted to come back and say that our amnio results came back and we have a chromosomally normal baby boy. i didnt have any complications from the amnio and i am currently 20 weeks pregnant.
thanks again for all of the information on your blog. it was very helpful in helping me understand my results a little better.
nancy
At Tue Sep 29, 08:17:00 PM 2009,
Anonymous said…
Hi
Im 38 years old and 13 weeks pregnant with my first child. I recently had the nuchal scan and associated blood tests and fohnd out my risk frfor DS was 1/2500 but for Trisomy 13 and 18 it was considered to be posutvie at 1/198Apparently in Australia the age related risk for Trisomy 13 and 18 is 1/207 but Ive read elsewhere that its 1/107. Do the age related risks differ between countries? My ultrasound was completely normal but I had low Papp a (.44) and low HCG (.23). What impact is the low HCG likely to have versus the low Papp a?
At Wed Sep 30, 10:14:00 AM 2009,
Kenneth F. Trofatter, Jr., MD, PhD said…
To Nancy Sep 17: Congratulations and best wishes for the rest of the pregnancy!
Dr T
At Wed Sep 30, 10:19:00 AM 2009,
Kenneth F. Trofatter, Jr., MD, PhD said…
To anonymous Sep 29: Both the hCG and the PAPP-A are VERY low and at your age, I am surprised the trisomy 18 risk assessment wasn't even higher. I am not sure why it isn't, but it may be because the hCG level is even lower than the PAPP-A. Often in trisomy 18, the reverse is true. Even if the baby is chromosomally normal (an, hopefully it is), you may still be at increased risk for problems commonly associated with a small placenta or poorly vascularized placenta, ie, small baby, preeclampsia, early delivery, etc. So, following the fetal growth and Doppler flow patterns may be important throughout the pregnancy. I wish you the best and please let us know how things turn out!
Dr T
At Tue Oct 20, 02:52:00 PM 2009,
Anonymous said…
Dr. T:
Can your height and weight affect low PAPP-A results? I am 5 ft and currently 106 in my 14th week.
No history of chromosomal abnormalities or heart conditions. I am 28 years old.
The doctor said the NT measurement came back fine: 2.3 NT and a nasal bone was spotted.
My blood came back as follows:
PAPP-A: .48
BHCG: 2.43
1/95 DS
Also, on the date of the test I was feeling sick and my heart was racing. The nurse even mentioned my elevated heart rate, which no one has ever mentioned to me before.
Thanks, Kristin
At Tue Oct 20, 05:24:00 PM 2009,
Kenneth F. Trofatter, Jr., MD, PhD said…
To Kristin Oct 20: Most laboratories factor your weight into the risk assessment. I am not sure how heart rate would affect the results. If you are really tachycardic, you might want to have your thyroid function studies checked, although early in pregnancy, elevated hCG levels can make you appear somewhat hyperthyroid because hCG cross-reacts with thyroid stimulating hormone! My recommendation would be to make your decisions regarding further testing based on the risk assessment value you have been given and how you feel about that result. Best wishes.
Dr T
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