labor nurse has been reborn and shares her experiences as a new nurse-midwife, woman, and blogger

Thursday, December 6, 2007

Screening Tests In Pregnancy

When a woman becomes pregnant, she is faced with making decisions about testing for fetal abnormalities. I have frequently seen women make these decisions without much thought, and end up in a quandary. (I have seen some go overboard thinking about whether they should do testing or not and drive themselves crazy with this, but not as often). The tests I am referring to are the screening tests for Down Syndrome, neural tube defects, and trisomy 18.

When I was working in an outpatient obstetrics office, it was my job to discuss the tests with the woman and give her information about the tests. Many times she would say, "I'll do whatever test is available to me" when asked if she wants it done. I really tried hard to discuss reasons why and why not to do the tests to present the full picture, but I felt that many were not listening to what I was saying.

So what tests am I talking about specifically? I am talking about screening tests done in the first and second trimester. Notice I emphasized screening, because none of these tests can diagnose a fetus with Down Syndrome, neural tube defects, or trisomy 18. They can only tell if the fetus may be at higher risk for one of the disorders.

The most common screening test is the Quad Screen. This is a blood test that is done between 14-20 weeks, but preferably between the 15-18th week. The Quad screen looks for fetuses that may be high risk for Down Syndrome, neural tube defects, and trisomy 18. It looks at 4 things in the woman's blood:

  • HCG (human chorionic gonadotropin)- this is a hormone produced by the placenta.
  • AFP (alpha-fetoprotein)- a protein released by the fetal liver.
  • Estriol- the estrogen of pregnancy produced by the placenta and fetal liver.
  • Inhibin-A- hormone produced by the placenta.

If one or a combination of these substances are abnormal (either too high or too low) may indicate a fetus at risk for one of the conditions. But, it does not detect all fetuses with these disorders, and sometimes falsely reports a fetus at risk who actually is not. This typically happens in cases with woman with a "positive" Quad screen. In other words, the sensitivity isn't 100%. Actually, the sensitivity is around 75-80%. About 2% of "negative" screens are falsely negative; or the test says the fetus is low risk but in fact does have one of the disorders. The results are reported in a ratio. For instance, it will say the Down Syndrome risk is 1:575 (which would be considered low or negative) or 1:15 (which would be considered high or positive). It will also give separate ratios for the neural tube defects and trisomy 18. This ratio is compared to the woman's age related risk. So for a 35 year old the age risk is about 1:240, but if she gets a ratio result that is lower than her age it is considered low risk.

Believe it or not, but that ultrasound you have around 18 weeks isn't just to determine the sex of your baby. It is also a screening test. The fetal survey (the second trimester ultrasound) looks at all of the fetus's organs and body parts. There are certain markers that are looked for that are associated with Down Syndrome or neural tube defects. I could go on in a separate post just about the fetal survey. I've found that not all ultrasounds are created equal; I've seen some pretty rudimentary ultrasounds and I've seen some very thorough scans. One marker seen are Echogenic foci that are bright spots seen on an organ (typically the heart) that may be associated with Down Syndrome. Sometimes the ultrasound is so sensitive that it's finding echogenic focus on organs that can't be explained, or little is known about.

A newer test, that will likely will become the standard, can be done in the first trimester that screens for Down Syndrome. Different places call this test different things, but I've heard it called Early Risk Assessment, Nuchal Translucency Screening, and First Trimester Screening. Many places only offer this to women 35 and older, or those who are high risk for having a baby with Down Syndrome. This test is done by obtaining a blood sample with an ultrasound between 10 and 14 weeks. The ultrasound measures the nuchal fold on the back of the fetal neck. The blood sample measures:

  • HCG
  • PAPP-A (pregnancy associated plasma protein-A)

Again, the results are given in a ratio and interpreted the same way as the Quad screen. One downfall to this screening test is that it can not predict neural tube defect risk, so if a woman wants a screening test for this she has to have the part of the Quad screen that looks at neural tube defects in her second trimester.

So what happens when a woman has a positive screening test? First she'll get an explanation of the results, and offered to speak with a genetic counselor. She can also chose to have a diagnostic test such as the chorionic villus sampling (CVS) or amniocentesis.

And why do I say that women do these tests that are offered without much thought? Because when the test comes back "positive" she has no clue what she wants to do. I feel that a woman should have a good idea what she would do with the information these tests are giving her. I've seen some women totally panic and freeze with fear that something is wrong, and can't come to a decision as to what she should do.

So here are some questions to consider when faced with whether or not to do these tests:

  1. Would having a child with Down Syndrome, spina bifida, or trisomy 18 change the outcome of your pregnancy?
  2. Would you feel that you could not adequately care for a child with those disorders?
  3. Would you terminate a pregnancy knowing you were carrying an affected child?
  4. Would you want to know if your child had one of these disorders so you could prepare for their care (ie, speak with specialists before the birth, align home help, decide whether to continue working)?
  5. Is not knowing in advance okay or would it create more anxiety?

I'm curious to hear how screening tests were discussed with you. I've seen some women just told that there is a test that is done and that they will be having it at that visit (so much for informed consent!). I've seen some providers tell women that they shouldn't have it done. Hopefully most are given accurate information that allows a woman to make an informed choice.


W said...

My wife and I were told about the tests and that's all. No comments one way or the other by the midwife. We decided to have them done since she is adopted and we had no idea what her family history is.

They told us it was a quad screen, but it included the nuchal translucency test with the ultrasound measurements. It had to be done before the end of the first trimester.

All the screens were positive, but it did diagnose twins. We were blissfully unaware for 17 weeks and a previous ultrasound.

Jess B said...

With all 4 of my pregnancies (3 different clinics with 2 different doctors), I was told that the next visit would be the such and such test to think about if I wanted to have it done. The only information I had on it was what I found online. I don't need to tell you how dangerous THAT is! Anyway, I figured since it wasn't going to change anything other than the care after the baby was born, why make myself sick worrying. Needless to say, we didn't have them done.

Ayslinn said...

Fascinating topic! I had excellent care for my 2 pregnancies. The first time I didn't have any of these tests done. I was more than 30 wks. when we figured out I was pregnant, and we had extensive genetic screenings and counseling to see if there was any chance the baby would be okay. The second pregnancy, my doctor explained it just about like you did, and I was given all the pros and cons and it was presented as an option. I chose it, on the theory that I'd like a chance to prepare.

Joanne said...

I'm not against these screening tests, but I am against offering these (not very accurate) "screening" tests to women without very thourough informed consent - and I fear that most OB's don't take the time to do that education before offering and administering these tests. It drives me bonkers!

With my first baby I did not have any tests done - not even an ultrasound. I just believed that everything would be OK. Thankfully everything did turn out OK.

I am a Monkey's Momma said...

If only I had been told what the 15 week blood test was all about...I had NO clue what a quad screen was until doing my own research before this current pregnancy. It was never explained to me by my OB or the mEdwife I switched to at 20 weeks. The ultra sound wasn't either.

Let me make it clear:

there was *NO* informed consent going on with me and my care providers.

This time around, the only u/s I'm having is to determine the placenta's location for my required HBAC consult with an OB. Other than that...I'm doing nothing.


Because it's my choice and this pregnancy will continue regardless of what some screening says. Sure, it's a leap of faith, but isn't anything involving having babies and being a parent a leap of faith?

Great post. Too bad most moms don't care enough to be educated on the choices they make. Even if their "choice" is doing everything they are told (you know, testing, VE's, constant EFM, AROM, inductions, etc).

Teresa said...

I had a less than optimal experience. They never asked me whether I wanted the quad screen. They just sent me to the lab without telling me what they were drawing up. I knew what they were doing and expressed my ambivalence to the phlebotomist, but she didn't really have a lot to contribute aside from a comment that "We really test for too many things and most people have completely normal pregnancies even if they have a positive screen.

Rinna said...

Discussed probably isn't the most appropriate word for my experience.
In a nutshell, it was offered to me and I was given a piece of paper with information on it.
Being the very information-obsessive person that I am, I researched it 'til kingdom come and when I learned about the high rate of false positives, I declined the test.
Of course this decision was made in conjunction with answering NO to (your) questions (1) and (3). A YES on (5). And a "We'll cross the bridge when we get there" on (2) and (4).

While I am all for informed consent and I do feel that somehow a lot of doctors just seem to glaze over that part, I am also for personal responsibility when it comes to decisions like these. As patients, we also have to be responsible to obtain information for any procedure done to us. There is a whole gamut of information available in books and the internet as well as other experts that one can consult with.

Wabi said...

Heh. Well, since you asked ...

The NT screening seems much more accurate than the quad screen in terms of low rates of false positives and false negatives. The fact it happens in the first trimester when you still have privacy (because you are not showing yet) and ending a pregnancy is potentially safer than it is later on is all good. And even if you opt to carry to term a baby with a serious genetic issue, I think the test is still very valuable. Knowing in advance that a problem exists is only going to increase the chances that your baby gets the care you deem appropriate after birth.

I felt my doctors and nurses did a good job of explaining the difference between a screening test (like the NT) vs. a diagnostic/invasive test (CVS or amnio, which run a small risk of ending a pregnancy). All that was also very good.

BUT, the place where I feel the medical folks around me failed was in making sure that my NT screening was scheduled early enough in the pregnancy testing "window" so that if a possible problem was discovered, I could still get a CVS to confirm or deny what was up. While I knew the windows for CVS and NT screenings were basically the same last few weeks at the end of the first trimester, nobody told me that there could be a lag in getting results back from the NT screening that might put me outside the window for a CVS.

This is precisely the situation I found myself in a couple years back. I had my NT screening done in the middle of the 13th week. I was already a few days past the CVS window when my NT results showed a 1 in 5 shot at either trisomy 18 or trisomy 13. And then I had to wait another month to get amnio results that confirmed the suspected T18.

Ultimately I decided to end my T18 pregnancy. But a termination at 16 weeks is very different than one done at 12 weeks. Complication rates are much higher. In fact, my uterus was perforated badly in the termination. Suddenly the T18 pregnancy -- something everyone assured me was just bad luck that didn't really impact future pregnancies, had permanent ramifications for me. Because after the perf, I was told the chance of uterine rupture during labor was five or ten percent, and no hospital would allow me to labor under those circumstances. It was going to be c sections for me from there on out if I wanted to try for another baby.

The ultimate kicker? My baby shoved her feet through the perf scar on my uterus before I ever went into labor during the next pregnancy. I was at home, in the 35th week. The baby and I are lucky to survive. Unfortunately, my uterus is now too damaged to attempt pregnancy ever again.

Looking back, I realize that the T18 issue would have been the same regardless of when I found out about it. But I can't help but think everything else -- the termination, the perforation, the uterine rupture -- might all have been very different if only the NP who counseled me on testing options had said, "If you want a CVS in the event of a crappy NT result, make sure you schedule the NT in week 11 or 12 rather than week 13."

One simple sentence of information left out of an otherwise thorough explanation. Just one sentence. But it might have made a really big difference in my life, had I heard it.

Cindy said...

Since I was over 35 when pregnant I was offered every screening test in the book. My nurses and doctors gave me a fairly level headed talk about the tests (pros and cons) and I did a lot of reading on my own. My husband and I decided early on that we would not terminate the pregnancy for Down's Syndrome or spina bifida, therefore, we refused all testing except the 20 week anatomy scan. As soon as I told our health care providers that any testing results would not change our minds about the course of the pregnancy, the topic of testing was dropped and never brought up again.

Real said...

After my fourth baby, we gave up on the screenings completely because no matter what was found, it wouldn't really change anything at all. We didn't see the need for ultrasound either and I wanted everyone to Back AWAY From The Baby and quit trying to sneak peeks into my body!

But baby #5 was measuring a little large for dates in months 7 and 8 and if I wanted to birth at the birth center I had to get one done to rule out any factors that would risk me out. I was fine. Just a big, thick uterus after 4 kids!

Baby #6 went all the way to 45 weeks before we finally decided to do an ultrasound because I had noticed some changes. We ended up going to the hospital for an induction. Worked out perfectly. Baby was fine.

Baby #7 had no screenings, no ultrasound, homebirth. finally.

This baby #8, may or may not be our last. Because it took us almost a month to name the last one, my husband wants a little warning about which gender to narrow the search to. So we're just going to fetal photo JUST to find out gender--no other screenings or measurements.

And still I'm a little freaked out. Even with the other ultrasounds, we haven't checked gender in more than a decade (I like the surprise!). The last time we did we found out we were having a boy when I wanted a girl. I was extremely disappointed and then felt guilty for the rest of the pregnancy for caring so much. I vowed I would never do that again. And yet, here I go on Saturday...

Anonymous said...

The first CNM that I went to basically just said that this is a test that can be done around this time to check for defects. She did not go into much detail, and did not discuss the accuracy at all. She said that some women want to know so that they can abort, and some don't bother because they will live with whatever outcome.

She did not pressure me either way, but did not give a lot of information about it either.

I ended up just choosing to go with the ultrasound. Although that one was not really presented as much of a choice.

Anonymous said...

I was given a good explanation of the screenings by my midwives (who practice at a big teaching hospital). They emphasized that it's not definitive, but only indicates the LIKLIEHOOD that the baby might have or not have a genetic defect. I am college educated and literate and did a lot of reading on my own, so I understood the tests and their purposes independently of the midwives' explanations. Man, it's all about biostatistics and relative risk assessment!

The midwives also said, "If you are cool with whatever comes out, there's no need for the tests. But, if you have certain limits to what you think you can handle in terms of defects, better to know now so you can either make plans for care, terminate, or quit worrying about it for the rest of the pregnancy."

They offer nuchal translucency testing and the quad screen as standard tests to all women, no matter what a woman's age, because of the small number of women in their 20s who end up with Down Syndrome babies and are angry that they weren't told they could have screened for it (read: avoidance of lawsuits).

The one thing it took me awhile to get straight: the "positive" and "negative" monikers -- usually positive means something good, and negative means something bad, but in this case it refers to the potential presence or absence of defects...

CrankyProf said...

My original practice told me that I WOULD have the quad screen done. When I politely declined -- abortion is not an option for me -- they dumped me, and I had to find a new practice. I literally walked out of the practice with all my records. Note: this was THEIR request; I would have stayed with them, and signed a waiver of some sort, but they felt the risk of lawsuit was too great.

The new guy discussed it with me much the way your post did -- and the b0ttom line was, if there would be no change in my decision -- i.e., the baby would be kept no matter what -- then I didn't have to have the screen done.

Labor Nurse said...

Thanks everyone for leaving your experience on this topic. I'd like to comment on Wabi's experience, and the fact that had she been counseled that she would need to schedule the 1st trimester screening before 12 weeks in order to do CVS. I am really glad that you brought this up because I don't think many people, including providers, think of this. I guess it boils down to communication between a woman and her provider. Even when we think we are doing a good job, things can get missed. Wabi's experience was terrible; I'm sorry that you experienced this and it's consequences. Thanks for sharing.

Nine Texans and friends.... said...

I refused all prenatal screening with my first 6 children. I consented to an AFP after an IEF was found during my anatomical screen. AFP came back low risk, went on to have a healthy baby.

Now I am AMA> I have consented to an integrated screen which combines the PPP-A and NT in the first trimester with the quad screen in the second trimester to give you a risk assessment.

The main purpose of consenting to these tests is knowing ahead of time if I have a sick baby I will deliver in a hospital with a Level III NICU instead of the usual place my OB catches which is down the street from the big Children's Hospital.

I am also hedging my bets that the screens will be reassuring and reduce anxiety instead of heighten it.

All that said, I can see how many if not most mom's haven't a clue what they are consenting to.
I have been pregnant...a lot. I worked in women's health. I understand these tests, how they are figured out, what they are looking at etc...but when the MFM doc was rattling off all my options I was overwhelmed. I can't imagine what happens when a first time, regular, non-medical couple goes and listens to the enumeration of tests how they choose, how the understand what they are choosing etc....

Teresa said...

I forgot to add: My quad screen was in week 19. I assume the results take a week to come back.

Seems like they didn't leave much room for a first trimester termination, no?

For reference, I live in South Georgia. Also, my OB referred out terminations.

Jaime said...

I knew about the screen prior to becoming pregnant. My husbands sister died in infancy from Spina Bifida. The first three children all had normal screens, my fourth child had an abnormal one.

It was a very frightening time. We were told I'd need to see a specialist in a nearby city but little was explained. I had to research on my own online for answers. In fact, when I tried to discuss with my OB what my options were he said I needed to just "wait and see" and not to "jump the gun". But considering I had to think about the possibility of ending my pregnancy I felt I owed it to myself and my family to think everything over.

I wasn't told anything about the amnio. The genetic counselor was the first person to give some solid answers. We also discovered the baby had tested low which meant the possibility of Trisomy 18or Down's.

Everything turned out fine but I lost alot of faith in my OB afterward. I didn't feel I got the information or support I needed from him or his staff.

Ashley said...

I was given an order for the testing. I asked the doctor if his wife had the testing. He said, "three times". I chose not to. The office seemed annoyed that I took the order but chose not to go through with it. I didn't care. My baby is mostly healthy. (Five weeks premature, slight respiratory problems at birth, no o2, formula intolerance*, possible gastrointestinal issue*)

*I breastfed for the first three weeks then dried up. Tried everything to get the supply back but was told that the drugs I was given is what "dried me up". He's been through multiple formulas and is finally doing okay on Elecare. We've been waiting over a month to get him in to see the specialist, 9 more days!

Jenny said...

I came in for a visit around 12-13 weeks, and the nurse started coming at me with a needle. I asked what it was for, and it was for testing for those things. She didn't explain what she was doing, nor did the doctor tell me that I would be tested on that visit.

I decided to not be tested partially because I didn't trust the nurse (with the needle, no less) and our son is our son, and we'd love him and care for him no matter what. Not knowing now means we'll have a lot of learning after he's born, should he not be neurotypical. But it's something we'll face and work through.

Anonymous said...

It was 22 years ago, but I remember the day like it was yesterday. The Ob called my wife and said "some test" had come back positive, and there was a chance our baby had Down's... Not something two brand new expectant parents need to hear. The internet didn't exist back then, and the OB, on a visit two weeks later, said, "There can be false positives, I just wanted you to know..." No offer of an ultrasound, no nothing but worry for another 20 weeks until a healthy baby girl was born.

Our second didn't get tested, all was well with her. Our last we had the test due to some concern regarding my wife's age; it was positive, but the OB did an immediate ultrasound and reassured us everything was fine...

I really don't think anyone should have the quad test, especially now that there are so many other reliable tests available

Ivory said...

What's interesting about this thread is the theme that some providers simply do not tell their patients what they need to know about their healthcare. But I've asked my doctor friends about that and they told me that their experience is that most people don't want to know.

My response - those of us who do need a little pin to wear with blinking lights that say "Explain Everything! I'm Interested!"

Melissa said...

I'm 21 weeks pregnant.

I was offered the 1st and 2d trimester screening tests. My midwife gave me information on each and encouraged me to ask questions.

I opted for both sets of screening tests. Prior to having them, my husband and I discussed next steps and what we'd do with various results. We decided that if a "positive" result was detected, I'd undergo CVS testing in the first trimester or amnio in the 2d. We further decided that we'd continue the pregnancy if the CVS or amnio revealed Downs Syndrome but if it found Trisomy 18.

We decided to have the tests for one of the reasons you mention: Preparedness. If the tests showed a likelihood of neural tube defects or Downs Syndrome, we wanted to arm ourselves with as much information as possible. We wanted to know so we could make better choices in selecting a pediatrician, feeding specialist/neurologist/surgeon (if necessary).

Tonia said...

I was given pretty thorough information. More so the second time (different doctor). I was also given time to ask any questions. I chose not to have the tests done and will do so for the remainder of my pregnancies. Knowing something like that wouldn't change my course of action and it would just make me stress even more during the pregnancy, since the tests are not a diagnosis.

Kristina said...

I actually stopped my OB from explain ing the quad screen as I already knew I didn't want it as it wouldn't change the outcome of my pregnancy. He pointed out that we live in a small area and that he felt if we had certain chromosomal outcomes that it would be a better plan to deliver at Big City Hospital several hours away, as they are better set up to deal with special needs infants. (Although we do have a NICU at my hospital, so I don't know how accurate that was...) I took him up on the quad screen.

Anonymous said...

I have had 6 babies, and have not always chosen the quad screen, but have a few times. The focus has always been on Downs syndrome...and spina bifida. I was told that the blood screen was to detect a chance for those disorders, and no real explaination. I declined the screen in my 16th week of one pregnancy, and the OB couldn't find a heartbeat right after that decline. She then said, "that's why we ask you to do the screening..." and then stopped. With my last pregnancy, the OB had me do the screening test and I just in my 15th week of pregnancy (15 day 1) according to sonogram as I didn't know the conception date with weird cycles while nursing. Screening came back 1 in 53 for Trisomy 18. I was stunned, scared, and didn't even know that was tested for. I found out all the information online, and we initially declined amnio. I was ready for amnio at my 2nd level 2 but the perinatal doctor said no based on good sonograms. I was always wondering throughout if there was a chance baby still had it, and I ended up with NST's and all sorts of extra sonograms because my OB was "checking" and I was watched carefully. My labor was also not normal, I was basically chained to my bed (figuratively, but it felt that way) and ended up with a baby in OP position, and was not allowed off the freaking monitor. Baby was born in the bag of waters intact, and healthy with no t-18. Still, we wondered after when no one said definitively that baby had no t-18. I didn't hear from the pediatrician for over 24 hours after the birth that my baby indeed did not have t-18. I was sure she was okay though since they didn't take her away to the NICU, but they did have to suction with a delee for mec, and during that 10-15 minutes on the warmer no one told me she was okay. That was very hard as I saw people around her, and knew it could have been my last time to see her if something was wrong but no one was saying anything and I couldn't even see her. My husband even took video of her and worried her feet looked wrong. All this because of a positive quad screen that was probably taken too early (I had her late and the later sonograms showed her off by one week on the due blood work was taken in week 14 probably). It was annoying! Besides, I was frustrated with my labor nurse for not letting me out of bed!



Anonymous said...

I just found this blog through Strollerderby - you are a wonderful, fascinating writer! This post caught my eye because just this situation caused me to switch OBs at 18 weeks (my son is now 18 months). The doctor I had came in, checked the chart, and announced, "Wow, already 18 weeks. Here's the prescription for your quad screen, you have to get it done by the end of next week so we can terminate if it comes back positive." My issue was not with the possibility of termination, though I personally would not have considered it. He NEVER asked what my feelings were, if I would consider terminating, nothing; just that callous assumption that all women would respond exactly the same way to that one possible outcome. Nor did he pause to explain what exactly the screening test was , and what "positive" would have meant. I never set foot in that practice again.

Aidan's mom said...

Great blog! This post caught my eye because there seems to be another emerging reason for the quad screen that was not mentioned. The first real sign of any trouble in my pregnancy was that quad screen. ALL 4 values were not within normal range. After ultrasound and an amniocentesis showed nothing wrong, we were left to scratch our heads and wait.

The perinatologist did comment to me that sometimes when more than 1 value is off it can be indicative of a preterm delivery.

I am SO glad I was prepared with that information. I watched myself like a hawk and at 24 weeks I developed PIH. At 26 weeks diagnosed with a clotting disorder and hospitalized. At 28 weeks I suffered from Class I HELLP and my son had to be delivered.

Just wanted to let your readers know that there are other reasons that are emerging as to why the quad screen provides valuable information.


Anonymous said...

I recently had an experience with the quad screaning. I was offered teh screaning early in pregnancy and took it as reccomended.I was 30 years old but my doctor screans everyone. I asked about my results at my next visit and he told me everything was great. I then had a routine ultrasound and the technician said she noticed a small white spot on teh babies heart. She told me this is sometimes seen in babies with down syndrome. I was terrified and went right to talk to my doctor about it. He said they should not have worried me like that, that I had nothing to worry about due top my age and negative screaning test and that everything was fine..My baby ended up being born with down syndrome as a suprize at birth...I do wish I was offered other tests when a marker was found on ultrasound rather than been reassured that everything was ok by my doctor..

Anonymous said...

I recently came accross your blog and have been reading along. I thought I would leave my first comment. I dont know what to say except that I have enjoyed reading. Nice blog. I will keep visiting this blog very often.


robin reed said...

I am 27 years old 3 pregnancy and I got a postive quad screen for the time my rato was1: 65 with is about 1.25% I was scared to death I was crying and didnt know what I was going to do. I went today for my level 2 u/s at 17 weeks and they didnt see anything abnormal baby weights 8 oz and everything measured normal. He wants me to come back in 4 weeks just 2 double look because the baby will b alot bigger. I asked him if this was him n his wife would he get the amio he said there is not right or wrong just options but they wouldnt get it because its less than 1.5% chance that baby would have downs. He was very good sweet and answered all questions. My husband and I have no birth effects on either side. I believe in MY GOD!!!!!!!!!!! WISH THE BEST LADIES