Homozygous α0-thalassemia is a serious autosomal recessive disorder with
poor fetal outcome and severe maternal complications. Conventionally, prenatal
diagnosis is performed by an invasive test. A non-invasive approach using serial
ultrasonography can effectively reduce the need for invasive tests in unaffected
pregnancies.
For two-dimensional ultrasound prediction, a total of 777 at-risk fetuses were
studied from 12 to 20 weeks between 1995 and 2006. At 12–15 weeks’ gestation, the
highest sensitivity (98.3%) was achieved by the combination of fetal cardiothoracic
ratio (CTR) and/or middle cerebral artery peak systolic velocity (MCA-PSV) at a
false-positive rate of 15.8%. At 16–20 weeks’ gestation, the sensitivity of CTR was
100.0%, but the false-positive rate was 5.2%. In contrast, the false-positive rate of
MCA-PSV alone was 1.4% and that of the combination of CTR and MCA-PSV was
0%, although their sensitivities were less than 65%.
In a cross-sectional retrospective study of 546 samples at-risk and control (268
fetal and 278 neonatal cord blood), the degree of anemia was only mild in 27.5% of
the affected fetuses (see chapter 3 for definition of mild anemia). Because MCA-PSV
is not very predictive of mild anemia, this may be one of the reasons why MCA-PSV
is not very sensitive in predicting an affected pregnancy.
A total of 832 at-risk pregnancies were studied using same noninvasive approach
at Maternal and Neonatal Hospital of Guangzhou (MNH) and Tsan Yuk Hospital
(TYH). The overall sensitivity and specificity of the noninvasive approach was 100%
and 95.6% respectively. At MNH, the need for an invasive test was reduced by 78.6%,
and all the affected pregnancies were diagnosed before 24 weeks’ gestation. After
adequate training and monitoring the quality of the subsequent ultrasound
examinations, the results achieved at MNH were comparable to TYH, with at-risk
pregnancies including the affected ones being seen at a more advanced gestation at
MNH.
In a retrospective review of 361 women at risk of carrying an affected fetus, 311
(86.2%) opted for the non-invasive approach using CTR and/or placenta. The cost
saving of this non-invasive approach was relatively small (HK$ 2,651) in comparison
to the cost of the whole prenatal screening program. On the other hand, the
non-invasive approach was more expensive than the direct invasive approach for low
MCV couples, as well as couples discordant for α-thalassemia and β-thalassemia.
ages. These results support the adoption of non-invasive approach in which routine
invasive test or karyotyping is no longer performed.
A total of 106 at-risk pregnancies and normal controls were prospectively studied
using three-dimensional ultrasonography. Placental volume (PV) at 11-14 weeks, and
PV/CRL quotient at 9-14 weeks’ gestation of affected pregnancies were significantly
greater than unaffected pregnancies (P<0.05). Using a cut-off point of 1.2ml/mm for
PV/CRL quotient to predict an affected pregnancy, the sensitivity, and specificity was
96.2%, and 100.0% respectively. / published_or_final_version / Obstetrics and Gynaecology / Master / Doctor of Medicine
| Identifer | oai:union.ndltd.org:HKU/oai:hub.hku.hk:10722/174391 |
| Date | January 2012 |
| Creators | Leung, Kwok-yin., 梁國賢. |
| Publisher | The University of Hong Kong (Pokfulam, Hong Kong) |
| Source Sets | Hong Kong University Theses |
| Language | English |
| Detected Language | English |
| Type | PG_Thesis |
| Source | http://hub.hku.hk/bib/B47454039 |
| Rights | The author retains all proprietary rights, (such as patent rights) and the right to use in future works., Creative Commons: Attribution 3.0 Hong Kong License |
| Relation | HKU Theses Online (HKUTO) |
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