Dr. Lam describes the role of a maternal-fetal medicine specialist and explains how this physician screens for fetal genetic disorders.
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Dr. Lam: Well maternal-fetal medicine specialists are people who have gone through residency training in obstetrics and gynecology and then have gone on for three more years of specialized training within the maternal-fetal medicine itself. Maternal-fetal medicine has also been known in the past as perinatology and our focus is on diseases of the mother and the fetus itself and how to treat those diseases or work with those diseases to accomplish an overall good outcome in pregnancy. Maternal-fetal medicine training is three extra years beyond residency at a specially accredited institution and we learn specific skills such as ultrasound, prenatal diagnosis, genetics, surgery, et cetera. Well there’s a couple of things that we can do to screen a baby for genetic disorders and the operative word here is that everything is truly optional; there is nothing that states that a patient definitively has to do anything to look for genetic issues within her fetus. Probably the most common ways to look for genetic issues are something called first trimester screening or the first trimester Ultra-Screen whereby we do an ultrasound of the baby between 11 to 13 weeks and pair that along with five drops of blood that we look for certain levels of hormone and together, those two factors will produce a mathematical estimate for that woman’s specific pregnancy for that baby to have either Down syndrome or something called trisomy 13 or 18. The next step is also some kind of level-2 ultrasound whereby we look at the baby’s full anatomy on an ultrasound between 18 to 22 weeks and we look for any structural issues that might arise. If any of these tests are positive moms may choose to do a diagnostic test and these are right now things called amniocentesis and CVS; whereby we are actually taking a sample of the baby’s cells and looking at the baby’s chromosomes exactly. What I want everybody to understand is that we cannot guarantee that we will find every genetic disease under the sun and it’s impossible to do that because most genetic diseases are caused by mutations within the DNA or the genetic code of a person and we have literally over a billion base pairs within the DNA and we can’t search for all those mutations. But with the help of ultrasound and with the help of diagnostic criteria such as amniocentesis or CVS we can look at the package, the way the DNA is packaged within the chromosome, look for physical defects within chromosome itself that may give us implications as to whether or not the baby has genetic issues or not.