Abnormal vaginal bleeding is frequently observed in the first trimester, occurring in more than one-third of pregnancies. Abnormalities in first-trimester pregnancy may be detected by transvaginal ultrasonography at routine examinations or in cases where abnormal vaginal bleeding occurs. Ultrasound baby scanning services Peterborough provides early dating, reassurance and viability scans from 6+ weeks.
Particularly, in high-risk patients, there is an increasing interest in the detection of structural abnormalities in the first trimester of pregnancy, if any. There are several factors that have contributed to this shift of interest from the second and third trimesters of pregnancy to the first one. The most 2 prominent causes are:
• Nuchal translucency measurements have now become available as an effective screening tool for Down Syndrome. As a result, more structural abnormalities are being detected in the late first trimester.
• Ongoing technical development of ultrasound equipment continues to improve the visualization of first-trimester fetal anatomic structures.
First-trimester ultrasound is done to confirm pregnancy and determine the location of the fetus; to identify the number of gestations and their viability, and most importantly to date the pregnancy since this stage is less prone to biological variations. The screening of the first trimester is done to assess aneuploidies and for the early detection of fetal anomalies.
The maternal age and gestational age of the fetus was the traditional method for screening of aneuploidies which led to increased invasive testing and ineffective identification of aneuploidies.
The risk of miscarriage is also associated with invasive testing. A combination of fetal nuchal translucency and maternal serum biochemistry is used to achieve screening for major aneuploidies. This strategy yields the identification of fetuses with major aneuploidies in about 90% of the cases with a false positive rate of 5%. Inclusion of other factors such as nasal bone, flow across the tricuspid valve, and flow in the ductus venosus, results in improving the detection rates (93–96 % ) and decreasing the false positive rates (2.5%).
Highly sensitive and specific additional first trimester markers such as nasal bone, facial angle, tricuspid regurgitation and impedance to the flow in ductus venosus are used in ultrasound baby scanning services Peterborough. Proper assessment of these additional markers improves the effectiveness of combined screening by increasing the detection rate and decreasing the false positive rate.