Pregnancy due date based on ultrasound dating

Most dating scans are done with a trans-abdominal transducer and a fullish bladder.If the pregnancy is very early the gestation sac and fetus will not be big enough to see, so the transvaginal approach will give better pictures.

5 ½ weeks gestation means 5 ½ weeks from the first day of the last menstrual period, which is usually about 3 ½ weeks from the date of conception (confusing, isn’t it!

) the fetus is clearly seen on trans-vaginal ultrasound and the heart beat can be seen at this early stage (90 to 110 beats per minute under 6 to 7 weeks, then 110 to 200 beats per minute as the baby matures).

the baby and its heart beat can be detected relatively easily with trans-abdominal and trans-vaginal examination.

This is presuming that the pregnancy is actually at this stage of development.

Sometimes a trans-vaginal examination shows that your pregnancy is less advanced than expected.

The earlier the ultrasound is done, the more accurate it is at estimating the baby's due date.Ultrasounds performed during the first 12 weeks of pregnancy are generally within 3 - 5 days of accuracy.The most accurate time is between 8 and 11 weeks gestation.This is because the fetus is growing so quickly that there is a big difference in size from week to week.Also the fetus cannot bend and twist too much yet, so the length of the body is fairly constant.However, the accuracy of the ultrasound examination is always dependent on the skill of the sonographer and the quality of the equipment.

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