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Ask Dr. D. Love Your Own Question
Dr. D. Love
Dr. D. Love, Doctor
Category: Medical
Satisfied Customers: 18772
Experience:  Family Physician for 10 years; Hospital Medical Director for 10 years.
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I think Im 6 weeks 3 days pregnant. I had a transvaginal ultra

Resolved Question:

I think I'm 6 weeks 3 days pregnant. I had a transvaginal ultra sound. They found a gestational sac measuring 16mm x 6 x 6. They don't think I'm as far pregnant as I thought. No yolk sac yet. How far pregnant am I ???? Do you take mean diameter and add 30. This would mean I'm 5.5 weeks pregnant. ( 16 +6+6 divided by 3 plus 30) is it normal not to see yolk sac yet.?? They said come back in two weeks. Should the gestation sac not be round ???
Submitted: 3 years ago.
Category: Medical
Expert:  Dr. D. Love replied 3 years ago.
Thank you for using JustAnswer. I will be glad to assist you today.

There are two factors that can affect assessments of gestational age - sac size and appearance of the yolk sac.

Our hospital uses a chart to determine gestational age based on the average sac. It actually is programmed into the software, so that there is no need for human calculation. With an average diameter of 9 (or 9 1/3), that would correspond to a gestational age of 5.5 weeks.

A yolk sac is usually visible by the fifth week of pregnancy, although there can be some slight variability.

Therefore, since a yolk sac is not visible, it is possible that you are actually 4-4.5 weeks, although it is possible that you simply have a later development of a visible yolk sac.

When the two measures are not in agreement, then the usual approach is to repeat the ultrasound, as your doctors are doing.

Gestational sacs are frequently not round, which is why we average the three dimensions. If the gestational sac was round, then we could simply use any diameter, since they would all be the same.

If you have any further questions or need clarification, please let me know.

Customer: replied 3 years ago.

If I was only 5 weeks could the sac measure the size it is ?? I'm worried in case nothing develops, I have morning sickness and tender breasts

Expert:  Dr. D. Love replied 3 years ago.
Yes. The ability to assess gestational sac size can be affected by many variables, including several that have nothing to do with the developing fetus, such as the specific equipment used, the relative position of the uterus, or whether there are any other anatomic structures, such as small fibroids in the uterus.

This is why we typically use both the sac size and the fact that there is not yet a visible yolk sac to give an idea of gestational age.

I can understand your concern about whether something will develop, but we typically are not worried about the absence of a yolk sac until the gestational sac average diameter has grown to 12 mm. At this point, though, this still could be an early pregancy, and the follow-up ultrasound will be better at assessign the pregnancy and determining gestational age.

In reality, once the fetus is visible, the crown-rump length is the measure that is most accurate in assessing dates, and the gestational age as determined by the crown-rump length will usually be considered the accurate assessment, and if there is not agreement between this ultrasound measurement of the gestational sac and a later ultrasound measurement of the crown-rump length, then the determination of gestational age by the crown-rump length will be used.

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