Ken Seethram, MD, FRCSC, FACOG (biography and disclosures)
What I did before
Previously, my practice in prenatal screening revolved around second trimester serum and sonography to identify markers in maternal serum, or ultrasound that would hint at a genetic problem. If these were identified, I would offer patients invasive testing such as amniocentesis.
What changed my practice
The European experience (especially the U.K.) shows that multiple ultrasound markers, serum, and anatomical survey of the fetus can be conducted in the period around 12 weeks, and that this information is much stronger in detecting genetic syndromes than 2nd trimester markers. These first trimester markers include ultrasound screening for nuchal (neck) translucency, nasal bone, ductus venosus (a new marker), and serum for genetic screening. Over 40 countries now do first trimester screening routinely in pregnancy. The North American experience has been stunted by patent disputes, and politics, but recently has revolved around combining first and second trimester markers (known as Integrated Pregnancy Screening, IPS). When set up as a contingency screening model, the literature suggests IPS detection rates are in the 87-88% range. Using a combination of first trimester markers i.e. NT (1992), serum pregnancy associated placental protein A (PAPP-A) and free beta hCG (1995), Nasal bone detection (2003), heart rate, and Ductus Venosus (2009) the overall detection rate for aneuploidy is 96% with a screen positive rate of 3%,
The largest drawback to IPS is that the reporting occurs in the second trimester, when women are starting to feel the baby move, and are developing a greater bond to the pregnancy. Several studies have shown that more than 85% of women prefer early screening (FTS). The FTS protocol is standard in most of Alberta and Ontario. In BC however, FTS is not insured, and with the complete markers, costs around $500.
What I do now
Although I continue to do second trimester anatomy scans and amniocentesis, a large part of my practice is the undertaking of first trimester screening. I also actively advocate for increased awareness regarding screening options. One of the most difficult things in my practice is trying to counsel patients regarding their options, and rates of detection, and then counsel regarding results. It is important to disclose to patients all the options available for screening – not every woman given the option to do more advanced screening will do it. For FTS, serum must be done at 10-11w and the sonogram at 12w (range 11=14w) for best performance. For IPS, the serum PAPP-A and NT is done at 10-12w, and the remaining serum at 16-20w. Either way, patients should be counseled early.
http://www.health.gov.on.ca/english/public/program/child/prenatal/earlyscreening.html
References:
Integrated screening for Down’s syndrome based on tests performed during the first and second trimesters N Engl J Med 1999;341:461-7 (Read the article)
First-Trimester or Second-Trimester Screening, or Both, for Down’s Syndrome N Engl J Med 2005;353:2001-11. (Read the article)
Ductus venosus Doppler in screening for trisomies 21, 18 and 13 and Turner syndrome at 11–13 weeks of gestation Ultrasound Obstet Gynecol 2009; 33: 512–517 DOI: 10.1002/uog.6330 (Request the article with CPSBC Library)
Prenatal Screening for Fetal Aneuploidy – SOGC CLINICAL PRACTICE GUIDELINE J Obstet Gynaecol Can 2007;29(2):146–161 (Read the article)
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I have several questions: 1.What are the options available to the parents if this 1st trimester screening indicate gross abnormalities in the fetus ? 2.How would the parents be counselled ? 3.What are the more common options the parents would decide on ?
If finding gross abnormalities is unlikely going to affect the ultimate decisions of the parents on learning of the finding of abnormalities with their fetus, then why bother doing these expensive tests and induce more anxiety or mental & ethical dilema and agony for the parents ?
Dr. Seethram,
Thank you for this well informed info bite. I struggle practicing in BC with the politics that surround this issue. I believe all women should have the right/access to this service and the right to decline it as well. As it stands, only well educated, wealthy women get their options early.
Dr. Anne Dobson (ob/gyn)
I thought that first trimester screening was just that….screening. You don’t discuss the need for confirmatory testing ie amnio, since the window for CVS is past by 12 weeks. Do you not consider this important?
To answer some of the questions:
Q: What are the options available to the parents if this 1st trimester screening indicates gross abnormalities in the fetus?
[Dr. Ken Seethram] If gross abnormalities are seen, including anatomic defects, patients could elect to proceed with CVS or directly to termination.
Q: How would the parents be counselled ?
[Dr. Ken Seethram] Full genetic counseling is required for parents, but full ranges of options are given.
Q: What are the more common options the parents would decide on?
[Dr. Ken Seethram] The most common options are CVS and amniocentesis
Q: If finding gross abnormalities is unlikely going to affect the ultimate decisions of the parents on learning of the finding of abnormalities with their fetus, then why bother doing these expensive tests and induce more anxiety or mental & ethical dilemma and agony for the parents?
[Dr. Ken Seethram] Its very different to find t18 at 12 weeks versus 20weeks. The psychological ramifications of a 20 week induction of pregnancy, versus a 12 week termination are entirely different, and may have very different risks for future reproduction.
Q: I thought that first trimester screening was just that….screening. You don’t discuss the need for confirmatory testing ie amnio, since the window for CVS is past by 12 weeks. Do you not consider this important?
[Dr. Ken Seethram] Well, the scans are ideally booked for 12w, such that if risks are elevated, and the patient decides, a CVS can be performed. You are right – all this is just screening, – it is the difficult job of genetic counseling afterwards to ensure that diagnostic testing is reviewed and risks disclosed in full detail.
This should be available for all pregnant women in BC. I appreciate all of Dr. Seethram’s efforts in educating health care providers of the benefits of 1st trimester screening.
“If finding gross abnormalities is unlikely going to affect the ultimate decisions of the parents on learning of the finding of abnormalities with their fetus, then why bother doing these expensive tests and induce more anxiety or mental & ethical dilemma and agony for the parents?”
As a mother choosing these tests, early results would give me more time to learn about what having a baby with one of these issues would mean. I would have more time to access support for after the birth, to learn about family support groups, access counseling and identify friends and family who can help through the difficult adjustments to what life with a diagnoses like this will mean. I would have more time to learn about the issues that I am likely to deal with. I would have more time to grieve the child I otherwise expected and come to begin to accept the child I am having as he or she is.