Fetus = approximately 1.25 mm long An experienced sonographer can detect a yolk sac with transvaginal ultrasound when the gestational sac has reached a mean diameter of 8 mm to 10 mm.The presence of a yolk sac confirms the diagnosis of an intrauterine pregnancy and excludes ectopic pregnancy, except in rare cases of simultaneous intrauterine and extrauterine gestations.You may have a earlier scan, if you are experiencing pain or bleeding for example or unsure of LMP dates.Transabdominal ultrasound (TAU) and also the transvaginal ultrasound (TVU) are valuable diagnostic tools in obstetrics and gynecology.One gestational sac seen with 2 yolk sacs visible inside it Identical (monozygotic) twins.This results from an early embryo dividing into 2 genetically identical embryos.The yolk sac is first visible at 5 weeks and it is always present by 5 weeks and 4 days.
First trimester ultrasonic scans may show 'soft' markers for chromosomal abnormalities, such as the absence of fetal nasal bone or an increased fetal nuchal translucency (back of the neck) to enable detection of Down syndrome fetuses.
With transvaginal ultrasonography, cardiac motion can sometimes be seen in a 2-mm to 3-mm embryo, and is invariably detected in normal pregnancy when the length of the embryo reaches 5 mm.
At the end of week 5, the heart rate is about 60 – 90 bpm.
Measurements taken at these early scans will help to; confirm a pregnancy, date the pregnancy and to see any problems that may occur in the pregnancy ( low lying placenta, twins etc.).
Scans in early pregnancy are usually performed in the first trimester around 12 weeks.