The prenatal diagnosis of fetal anomalies started with the development
of X-ray. In 1943, Hartley and Burnet, Radiologists in Manchester (J
Obstet Gynaecol Brit Empire,1943;50:1-12), reported a series of 11 cases
of “croaniolacunia” or lacunar skull, a condition often associated at
births with spina bifida or encephalocele. These cases were all
diagnosed in the third trimester of pregnancy and the radiograph
features believed to be due to the effect of increased intracranial
pressure on the fetal skull of hydrocephaly. Until the end of the 1960s,
radiography remained the main technique to diagnose congenital
abnormalities. In 1969, Russell (J Obstet Gynaecol Br
Commonw,1969;76:345-50), also a consultant radiologist from Manchester,
compared the accuracy of antenatal radiology examinations with
paediatric reports in the diagnosis of anencephaly and other major
neural tube defects, skeletal abnormalities such as achondroplasia and
severe exomphalos when associated with rib deformities. Overall, the
accuracy of the radiological diagnosis was considered as “strikingly”
accurate for neural tube defects with 88 out of 113 cases of anencephaly
diagnosed before delivery. Although, the author did not provide the
gestational age at diagnosis, the images included in the article
indicate that these were obtained in the third trimester. As neonatal
care and surgery were in their infancy at the time, the main objective
in diagnosing these anomalies was not the fetus but the need to identify
antenatally mothers at risk of obstructed labour.
Not surprisingly, some of the first publications by the team of Ian
Donald in Glasgow were on the antenatal use of ultrasound imaging in the
evaluation of the size of the fetal head (Willocks et al., J Obstet
Gynaecol Br Commonw,1964;71:11-20). The fetal head was the only
structure that could be measured and biparietal diameter the only
measurement that could be obtained with the “ultrasound beam” of the
first ultrasound machine (Figure). The technique called “cephalometry”
was used at the end of the third trimester to assess “growth and
maturity” of the fetus and “disproportion” and was found to be more
reliable with ultrasound than X-ray. It would be another decade, before
ultrasound imaging could reliably identify fetal anomalies such as
spina-bifida in the second trimester of pregnancy (Campbell et al.,
Lancet,1975;1(7920):1336-7). However, the use of ultrasound imaging in
the mid-seventies to search for major neural tube defects was always
triggered by high levels of maternal serum alpha-fetoprotein. As there
were few ultrasound equipment available and few trained operators, this
biomarker was to remain for two decades the first line of action in the
antenatal screening strategy for spina-bifida. The advent of
high-resolution imaging, access low-cost and mobile ultrasound equipment
and the training of more specialists and sonographers has moved the
antenatal screening and diagnosis of many fetal anomalies to 11-14 weeks
of gestation (Ushakov et al., UOG,2019;54:740-5).
The systematic review by Drukker et al. (BJOG 2020) brings the focus
back to late pregnancy: even in our exciting modern era of early anomaly
scanning, a fetal abnormality will still be found in about 1 in 300
women scanned in the third trimester.
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