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Fruit of the Womb
Fruit of the Womb

Reader's Questions Related to Low PAPP-A in First Trimester Screening for Aneuploidy

The following comments and questions were left on my previous post regarding Low Pregnancy-Associated Plasma Protein-A (PAPP-A) and Pregnancy Outcome. The questions are excellent and summarize the concerns of many of our readers who have a low PAPP-A value detected at the time of first trimester screening for aneuploidy, so I thought it worthy of a full post. My responses are in italics after each of her questions.

• At Sun Mar 23, 02:20:00 PM 2008, Anonymous said…

First of all I want to thank you for this wonderful website. This is the best PAPP-A site on the internet, and believe me I have seen all of them.

These are my first trimester screening results:

Nuchal (translucency) scan was normal
Free beta hCG: 0.7677 MoM
PAPP-A: 0.1358 MoM

This PAPP-A put me in high risk of a chromosomal abnormality. I did CVS (chorionic villus sampling) and results were normal. Now I am worried about nonchromosomal issues like placental dysfunction and restricted fetal growth. I have a number of questions:

1) For the blood test they dated my pregnancy based on the scan as 13 weeks. I am sure that I was 12wk 3d or 12wk 4d only. I read that PAPP-A doubles each 3 or 4 days during first trimester. I wonder if the result would not be so low if they would have dated my pregnancy as 12wk 3d or 12wk 4d. Would it be 0.2716 MoM instead of 0.1358 MoM?

Dr T: 3-4 days should not make any significant difference in the interpretation of the test and the MoM does not change at the same rate as the PAPP-A.

2) The fact that hCG is also low, does it mean anything?

Dr T: The hCG is NOT especially low.

3) What is the risk of placental dysfunction with PAPP-A levels as low as mine?

Dr T: The lower the PAPP-A, the greater the risk for intrauterine growth restriction and other complications (I answer this point more specifically in my post on “The Affect of Smoking on PAPP-A levels Detected in First Trimester Screening” on March 25, 2008)

4) I am a non-smoker but I am a passive smoker, could this influence the PAPP-A levels?

Dr T: Passive exposure to cigarette smoke could potentially reduce the PAPP-A levels (again, see the March 25, 2008 post) although I have never seen that addressed in the scientific literature! Maybe you should make the smokers in the family “take it outside” for your baby’s sake!

5) During the nuchal translucency scan, the baby’s size was found to be normal or even big for the age. Is this a good sign or it is irrelevant?

Dr T: I would rather see a larger baby than a smaller one at this point although it's probably irrelevant! Abnormalities of placentation usually are not reflected in effects on fetal growth until after 20 weeks’ gestation.

6) I have been advised to have a scan at 28-30 weeks to assess fetal growth. Should my doctors start monitoring this earlier? If there is placenta dysfunction, does it only start in 3rd trimester or could it start earlier? If the latter, wouldn't it be better to start monitoring earlier? You recommend serial assessment of fetal growth, what is the frequency and when to start? Same question for the Doppler.

Dr T: Placental dysfunction can lead to intrauterine growth restriction (IUGR) much earlier than 28-30 weeks. Although low PAPP-A levels are not invariably associated with IUGR, yours is low enough that I would consider assessment of growth at 24-26 weeks. If there is a significant abnormality of placental vascularization (not just a small placenta), Doppler flow studies can often detect those that early, even before the baby starts to fall off the growth curve. If growth and Dopplers are normal at that time, I would probably repeat both studies about 4 weeks later (28-30 weeks). Based on that later study, I would then decide if further fetal evaluation is necessary.

7) Is it worth buying my own blood pressure monitor to control the preeclampsia risk? My doctor will only test me every 3 weeks.

Dr T: Just go to a local pharmacy. Most of those have blood pressure devices that you can use for free and they are more accurate than if you did it yourself (P.S., Remember to relax and uncross your legs while you are having your BP checked!).

8)Is the low PAPP-A level and placental dysfunction related to the age (I am 36) and do I have more chance of having the same issue in a future pregnancy?

Dr T: It is conceivable that your age is contributing to a suboptimal site for placentation if you have had, for example, many previous pregnancies or D&Cs, or have a uterine septum or adhesions, or uterine fibroids. Chance of recurrence is going to depend on why it happened this time! One of the old adages in obstetrics, however, is that "history tends to repeat itself" even if we aren't smart enough to figure out why!

9) Is there a link between restricted fetal growth and cerebral palsy?

Dr T: There is a greater risk for both cerebral palsy and developmental problems in growth restricted babies that is dependent on the actual reason for the IUGR. Examples of causes for IUGR include congenital infections such as cytomegalovirus (CMV), chromosomal abnormalities, genetic problems or syndromes, placental insufficiency, premature delivery, and maternal preeclampsia are the most common.

Anyway, I hope this helps. Any more and I would have to send you a bill for my time! (JUST KIDDING). Great questions and good luck for the rest of the pregnancy. Let us know how things turn out, MJ!

Dr T
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