•Routine Diagnostic Tests During The Antepartum Period:
A.IMAGING ULTRASOUND AND DOPPLER TECHNIQUES
Ultrasound pulses, which are sent into the body and produce echoes as they bounce off organ boundaries and within tissues, are ultra-high-frequency sound waves, which extend far beyond the normal range of acoustic vibration, falling between 2 and 10 megahertz, or 2 to 10 million cycles per second. These echoes are picked up by a transducer, and further converted as scan lines on a display monitor to form a picture of the underlying tissue from the emerging pattern of these waves.
Doppler techniques, that are employed in specialized scans, fetal monitors, and handheld fetal stethoscopes, use higher and continuous waves of pulses than used in ultrasound.
Furthermore, in order to assess the relative thickness of the nuchal (neck) skin surface and the soft tissues at the back of the baby's head at 11 to 14 weeks gestation, a Nuchal Translucency (NT) test--another application of ultrasound technology--is performed. NT is used as a screening marker for Down syndrome and is associated with a number of other fetal abnormalities and genetic syndromes. An increased NT by itself is not considered a fetal defect and 5% of babies detected with increased NT will be found normal by an invasive test.
Additionally, ultrasound scans are increasingly used to assess specific markers such as the amount of amniotic fluid (AF) as well, with indices below or above the normal reference ranges labelling the pregnancy as high-risk.
Although it is true that when used to investigate a possible problem at any stage of pregnancy, for instance prenatal bleeding and possibility of a miscarriage, or fetal growth restriction, information gleaned from ultrasound may prove to be a vitally helpful piece for the parent's decision making process. However, it's the routine, standard scanning--in the absence of any evidence of complications to pregnancy--mostly done in order to estimate the size of the baby, and estimate due dates (EDD)--that has been a subject of great concern from researchers and scientists since long. Touted as transforming ‘the very experience of pregnancy’ (Petchesky, 1987), routine ultrasound technology has ushered in an era where more and more physicians have lost the art and skill of manual abdominal palpation to determine fetal lie and position, and the ability to determine fetal well-being with auscultation (listening) of fetal heart tones using a fetal stethoscope.
Statements questioning the safety and usefulness of routine scanning have been reiterated across several platforms. Considering that the technology was introduced as a routine part of clinical obstetrics without adequate data for its safe use as a diagnostic tool during pregnancy, it's unsurprising that it was called "the biggest uncontrolled experiment in history" (Beech & Robinson, 1993). In a prestigious U.S journal, Epidemiology, a 2002 review of the safety of ultrasound in human studies stated: "Continued research is needed to evaluate the potential adverse effects of ultrasound exposure during pregnancy. Until long-term effects can be evaluated across generations, caution should be exercised when using this modality during pregnancy."
"...the biggest uncontrolled experiment in history..."
Moreover, a 2015 Cochrane Collaboration's study on routine late pregnancy ultrasound screening and its effects on maternal and infant outcomes concluded: "Based on existing evidence, routine late pregnancy ultrasound in low-risk or unselected populations does not confer a benefit on mother or baby. There was no difference in the primary outcomes of perinatal mortality, preterm birth less than 37 weeks, caesarean section rates, and induction of labour rates if ultrasound in late pregnancy was performed routinely versus not performed routinely."
The American College of Obstetrics and Gynecology (ACOG) issued a technical bulletin in 1984 stating, "No well-controlled study has yet proved that routine scanning is of benefit in the outcome of pregnancy."
This statement still holds true today.
The RADIUS (routine diagnostic imaging with ultrasound) trial evaluated the use of ultrasound in 15,151 pregnant women and concluded that routine scanning did not improve perinatal outcomes in low-risk women; and that while more fetal anomalies were detected in the group that had the most scans, this did not influence newborn survival rates (Ewigman, et al., 1993).
Both the Canadian OB-GYN Society and American Institute for Ultrasound in Medicine (AIUM) stand with believing that evidence is lacking to correlate human bio-effects and ultrasound exposure, they otherwise state that ultrasound should only be used for diagnostic purposes when clearly indicated (Gregor, 1993).
Needless to say, a substantial bulk of research explores the physical aspects of the implications of ultrasound imaging on the body, almost deducting the emotional and psychological effects of these results on the mother from the total equation. Variables such as training and skill of the sonographer, the quality of the instrument used, possibilities of false positive and false negative findings, as well as a huge gap in acquiring accurate detections for fetal abnormalities--that can range from 4-70% in detecting cardiovascular defects (Nolan, 1993) for example--all of these expose 'the expectant mother to uncertainty and possible anxiety about the health of her baby that has implications that may be far reaching. In addition, little is known about how the baby that was compromised in the uterus develops after birth and in the first years of life' (Bricker et al., 2015).
References:
- Salim Al-G, Angela D. Transforming pregnancy since 1900.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4726727/
2. Merry-K M. Prenatal Care: Limitations and Opportunities.
https://drive.google.com/file/d/1AEv6s0q8W71R7-OZH7p3y6fLUyiSCrlh/view?usp=drivesdk
3. https://m.acog.org/Patients/FAQs/Routine-Tests-During-Pregnancy
4.Bernard G. Ewigman, James P. Crane, Fredric D. Frigoletto, Michael L. LeFevre, et al. Effect of Prenatal Ultrasound Screening on Perinatal Outcome.
https://www.nejm.org/doi/full/10.1056/nejm199309163291201
5. Michael L.LeF, et al.,, RADIUS (Routine Antenatal Diagnostic Imaging with Ultrasound) Study Group. A randomized trial of prenatal ultrasonographic screening: Impact on maternal management and outcome.
https://www.sciencedirect.com/science/article/abs/pii/000293789390605I
6. Bricker L, Medley N, Pratt JJ. Routine ultrasound in late pregnancy (after 24 weeks' gestation) to assess the effects on the infant and maternal outcomes.
Image Credits:
[Top: Edward Cisneros at Unsplash]
[Bottom: Sharon McCutcheon at Unsplash]