The 11 - 13 week first trimester scan - more detailed information.

Throughout the nineties we have sought to identify the best use of ultrasound in the first half of pregnancy, differentiating between the limitations of ultrasound and its users, constantly trying to provide the most accurate data on the capability of this investigation. Ultrasound manufacturers have taken advantage of revolutionary developments in computer technology to produce machines and transducers with ever-greater resolution, particularly at higher frequencies.

These machines, whether transabdominal or transvaginal, have made routine investigation in early pregnancy a reality. Early pregnancy dating, confirmation of viability (see Threatened miscarriage), diagnosis of multiple pregnancy and abnormality, can now be attained with a 10-14 week scan. It is therefore apparent that much of what is currently achieved at the mid-pregnancy assessment can be fulfilled by the 12-14 week scan. Although earlier diagnosis includes pregnancies that would have been lost through the process of natural wastage, it allows women to make decisions about their pregnancy at a much earlier stage than before. Invasive prenatal diagnostic testing can also be offered at this stage, accepting the potential dangers of early chorionic villous sampling and early amniocentesis.

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