Most women go to a prenatal ultrasound appointment with the expectation of seeing the baby and getting some cute pictures for the baby book. Forgotten by most is the reality that this is a medical test, done for specific medical reasons. Getting one, two, or even more scans during pregnancy has become an expectation and for most moms, the most important questions are 1) is there more than one baby? And 2) is it a boy or a girl?
From the health care provider’s point of view, question #2 is irrelevant, and question #1 is only one of a series of questions that ultrasound exams are expected to answer. The following statistics are from an article out of Canada.
In the first trimester (12-13 weeks after the last menstrual period), routine ultrasounds are used to identify such issues as clarifying the gestational age of the pregnancy, the number of babies conceived, identifying the up to 20% of pregnancies with such serious problems that miscarriage is inevitable, finding the approximately 1.2% of ectopic pregnancies – and increasingly looking for ‘soft markers’ of genetic or structural anomalies. The most significant finding for which sonographers look is the ‘nuchal fold thickness’ – basically a measurement of the thickness of a fold at the back of the neck. An abnormally high thickness can be the earliest sign of some chromosomal problems, such as Down Syndrome.
In the second trimester (14-28 weeks) ultrasound screening will find a major structural problem in the baby about 1.1% of the time, and will also find ‘soft markers’ for chromosomal and other genetic abnormalities about 3.6% of the time. Some of the more commonly identified ‘soft markers’ include short femur ( the thigh bone), mild pyelectasis (enlargement of the kidneys) echogenic bowel and intracardiac foci (bright spots in the bowels and the heart), borderline ventriculomegaly (slight enlargement of parts of the brain <
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