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Dr. Andrew Rynne
MD
Dr. Andrew Rynne

Family Physician

Exp 50 years

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Are There Any Alternate Tests For Ultrasound?

Hello. I am having an issue with an ultrasound that I had today to determine the gestational age of my baby. My date of conception which is the one time I was sexually active in the past year is 03/26/11 so I expected to be around 5-6 weeks, however at my ultrasound today I was told with assurance I am 7 weeks and 3 days. Could it be possible for the ultrasound to be off by 2 weeks
Mon, 17 Aug 2015
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OBGYN,  's  Response
Hallow dear,

The ultrasound dating of the pregnancy is done by the different lengths and diameters of the products of conception. If the length of the embryo is larger, it will reflect more gestational age.

The ultrasound aging can very by about 1 weak + or -. As the pregnancy advances, this difference gets minimized. So 6 weeks pregnancy can be reported up to 7 weeks. Personal error or variation also has to be kept in mind.

Moreover, the pregnancy may not happen exactly on the day of intercourse. The life of sperms is 72 hours and that of egg is 24 hours. However, if fertilization has taken place later, the dating should show smaller.

If you are so confident that the pregnancy is after a single episode of intercourse, you should stick to that date for your all further calculations.
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Are There Any Alternate Tests For Ultrasound?

Hallow dear, The ultrasound dating of the pregnancy is done by the different lengths and diameters of the products of conception. If the length of the embryo is larger, it will reflect more gestational age. The ultrasound aging can very by about 1 weak + or -. As the pregnancy advances, this difference gets minimized. So 6 weeks pregnancy can be reported up to 7 weeks. Personal error or variation also has to be kept in mind. Moreover, the pregnancy may not happen exactly on the day of intercourse. The life of sperms is 72 hours and that of egg is 24 hours. However, if fertilization has taken place later, the dating should show smaller. If you are so confident that the pregnancy is after a single episode of intercourse, you should stick to that date for your all further calculations.