The diagnosis of missed abortion is usually made by serial ultrasound scans demonstrating lack of gestational development.For example, if ultrasound scan demonstrates a 7mm embryo but cannot demonstrable a clearcut heartbeat, a missed abortion may be diagnosed.A short history of the development of ultrasound in pregnancy can be found in the History pages.Ultrasound scan is currently considered to be a safe, non-invasive, accurate and cost-effective investigation in the fetus. The gestational sac can be visualized as early as four and a half weeks of gestation and the yolk sac at about five weeks.Movements such as fetal heart beat and malformations in the feus can be assessed and measurements can be made accurately on the images displayed on the screen.Such measurements form the cornerstone in the assessment of gestational age, size and growth in the fetus.Dating with the CRL can be within 3-4 days of the last menstrual period.(Table) An important point to note is that when the due date has been set by an accurately measured CRL, it should not be changed by a subsequent scan.
The information obtained from different reflections are recomposed back into a picture on the monitor screen (a sonogram, or ultrasonogram).c) The Femur length (FL) Measures the longest bone in the body and reflects the longitudinal growth of the fetus. It increases from about 1.5 cm at 14 weeks to about 7.8 cm at term.(Chart and further comments) Similar to the BPD, dating using the FL should be done as early as is feasible.At 5-8 weeks a bradycardia (less than 90 bpm) is associated with a high risk of miscarriage.Many women do not ovulate at around day 14, so findings after a single scan should always be interpreted with caution.