How Essential is an Ultrasound Scan in Pregnancy

Published in Panorama



Pregnancy Ultrasound Scan … a must???


Rita felt as reassured as she was fascinated by what she saw on the screen: her baby’s heart was beating and he was moving, contrary to what she feared, following some vaginal bleeding; in fact, he was even smiling! All thanks to the magic of the 3D/4D ultrasound. This reassuring ultrasound, vital for the bonding between mother and child while the baby is in the womb, is only one of the many benefits of the ultrasound as an invaluable tool in obstetrics and gynaecology, explains Dr.Ulrich Honemeyer, Specialist in Gynaecology and Obstetrics, Welcare Hospital. The 3D/4D ultrasound, the latest in obstetrical ultrasound technology, enables us to see the fetus live in movement, to recognize surface defects of the baby like cleft, club feet, spina bifida, in addition to its internal organs and any malformations in them.”

The “window into the womb”, Ultrasound, or sonogram in pregnancy, uses high frequency sound waves to form an image of the uterus, placenta, and fetus. Beginning on a firmly reassuring note, Dr.Ulrich emphasizes that this non-invasive or at times, very minimally invasive diagnostic technique, is neither painful, risky nor harmful in any manner to the pregnant woman or her child. Instead it provides loads of information in determining and evaluating fetal health, to diagnose twins, check for a breech birth, the child's gestational age, to recognize malformations, congenital & chromosomal abnormalities, to determine the baby's gender and to determine the cause of vaginal bleeding in early pregnancy. “Bleeding in very early pregnancy, lower abdominal pain and positive pregnancy test, will all definitely bring in ultrasound as a diagnostic tool to see whether we are dealing with an ectopic pregnancy which is rather frequent here in the Middle East.”

According to Dr.Ulrich, ideally, ultrasound investigation should begin whenever a pregnancy can be stated, foremost, to know whether the pregnancy is inside the womb or if it is ectopic. “Ultrasound helps to recognize if a pregnancy is not intact. We have a spontaneous fetal loss rate of about 4% of all pregnancies until 12 weeks. This loss rate is due to severe anomalies in the fetus which leads to an abortion as a natural self-protective mechanism. We start very early with ultrasound and in about six weeks, we can already recognize the baby’s heartbeat. The 6th week is a time landmark in the development of the fetus because from then on we can monitor whether the pregnancy is developing normally.”

Talking of normal pregnancies would mean that the fetus may suffer less severe anomalies which do not lead to spontaneous abortions, like trisomia or Down’s Syndrome, explains Dr.Ulrich. In any general population of pregnant women, 1/800 may deliver a Down’s Syndrome baby; 5/1000 live births may involve babies with heart malformations or other congenital malformation syndromes, reveals Dr.Ulrich.

Ultrasound scanning in pregnancy is again invaluable in identifying twin pregnancies. Dr.Ulrich explains, “A membrane or wall between the babies, serves to separate twins. The degree of thickness of this membrane, or the absence of the membrane itself, may increase complication rates in such pregnancies. Where the wall is absent, we have a very high complication rate due to vascular connections between these twins which may lead to one of them growing very much and the other not growing at all. If such a condition exists, we need to recognize and analyse it so that it may facilitate the decision to deliver the babies prematurely to prevent fetal loss.

A large group of babies do not grow according to expectations, which may in fact, be the first indication that the baby may have a chromosomal abnormality. Dr.Ulrich elaborates, “It could be the first signs to show that the placenta is not working properly, in which case the baby is deprived of sufficient nourishment and therefore fails to thrive. A colour Doppler ultrasound scan will be able to pick up this condition. Once the condition is identified, it will enable us to decide whether the baby can cope with this placenta “insufficiency” or whether we’ll have to prematurely deliver the baby if it shows no chance of surviving in the womb. The usefulness of this scan cannot be underestimated since it tells us about 10 days in advance whether a baby is coming to the critical point! While the conventional method, the CTG, can give this information only 3 days before the critical point, thus shortening the time for taking remedial measures.”

Dr.Ulrich emphasizes the importance of ultrasound screening, in the first trimester of pregnancy between the 11th and 14th weeks, in particular. Termed the Combined Nuchal Translucency Scan & Biochemistry, this is a screening for chromosomal defects like Down's syndrome. “Nuchal translucency is a collection of fluid under the skin at the back of a baby's neck at 11-14 weeks that can be measured using ultrasound. While all babies have some fluid, in many babies with Down's syndrome, the nuchal translucency is increased. The scan can diagnose Down’s Syndrome with 60% accuracy and 40% accuracy in the case of heart malformations. Based on this screening, further diagnostic test CVS or amniocentesis may be done to get a conclusive diagnosis.”

Elaborating the importance of this scan Dr.Ulrich reveals, “It is required to accurately date the pregnancy, to monitor the baby’s growth and the check whether it is growing according to normal expectations or not. The sonographer will measure the baby from the top of its head to the bottom of the spine and the width of the nuchal translucency.”

The 2nd trimester, Targeted Ultrasound scan between the 18th and 23rd weeks of pregnancy is another very important landmark because in 18 weeks, the formation of the organs in the baby is complete, reveals Dr.Ulrich. “From 18 weeks, we will be able to recognize malformations of the organs. This does not, of course, include all heart malformations because the heart as a pump will show reaction to certain malformations only by muscular changes which may be recognized only in later pregnancy. Anyway, this scan is done if we suspect Down’s Syndrome by the earlier nuchal translucency scan.”

Once again Dr.Ulrich emphasizes, “I would advice every pregnant woman to have both these scans. No matter the issue of pregnancy termination if the baby is found to have serious or devastating anomalies, the investigative outcomes are important from other aspects. What about a baby in whom we trace a heart malformation by the screening process at 14 weeks which we again reconfirm by the detailed ultrasound scan at 20 weeks? Well, the baby’s anomaly is not going to be a problem in the pregnancy itself, but with a complete change in the fetal circulation after birth, the baby may face a life-threatening problem unless it is delivered in a Heart Centre and can be operated soon after birth! Definitely, the success rate of operations when they are done soon enough following birth, after it is known that such a problem exists, is not too bad in several types of heart malformations.”

What is the duration of a pregnancy ultrasound investigation? Dr.Ulrich explains, “To measure the nuchal translucency, we have to have the baby in profile and wait until it has one of its jerking movements phases. This takes about 10 minutes, until we get the right posture of the baby, a lateral view of it. The targeted ultrasound will take about 30 – 45 minutes since we need to scan the whole body of the baby – from the surface to the interior, from the top to the bottom, from the extremities, the umbilical cord, placenta and mother’s uterus. Sometimes we may also have to look at the mother’s kidneys. This happens when the mother may have a typically pregnancy-associated problem – an enlarged collecting system of mostly, the right kidney due to the compression of the ureter by the uterus. This may lead to the distension of the right kidney and if the flow of urine is disturbed, then it enhances the chance of infection.”

What does the ultrasound procedure involve? Pregnancy ultrasound scan may be vaginal or trans-abdominal, explains Dr.Ulrich. “During a trans-abdominal ultrasound, lubricating gel is applied to the abdominal skin so that the probe can be moved around to produce real time images. Ultrasound is similar to audible sound in that it can pass through water and human organs easily, but it can't pass through air or bone. The gel serves to bridge the gap between the skin and the probe. We need the mother to have a full bladder to make the scan effective. The vaginal probe on the other hand, is the first choice or preferred mode of doing an ultrasound scan since the probe is in direct contact with the uterus and therefore gives a clearer picture,” explains Dr.Ulrich.


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