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Pregnant. Done with ultrasound scan. What are the findings in the report?

Mar 2013
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Practicing since : 1998
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My wife is pregnant second time, we have a healthy boy at 3 years. I took her for a 8 week ultrasound scan.

The report is below

Single alive intrauterine fetus seen with unstable lie at present with presence of cardiac activity HR - 143bpm.

Fetal Parameters :

CRL - 10.6mm - 7 wk 1 days
GS - 33mm - 8 wk 3 days
Yolk sac measures approx 6.4mm
No evidence of subchorionic hemorrhage
Cervical Length measures approx 41mm XXXXXXX os is closed.
Corpus luteum is seen in left ovary.
Bilateral adnexae appear normal.
Average GA by AUA is 8 wk 0 days
EDD by AUA is 31/05/2014

Average GA by LMP is 7 wk 3 days
EDD by LMP is 04/06/2014

Doc sais everything is fine and suggested for NT scan five weeks from now.

What concerns me is the Yolk sac when I read on the net, all the info points that Yolk sac should not measure more than 6 mm. Please let me know if I should be worried and if I need to go for a subsequent scan not to wait until NT scan.
Posted Fri, 8 Nov 2013 in Pregnancy
Answered by Dr. Aarti Abraham 1 hour later
Brief Answer:

Detailed Answer:
Hello XXXX
Thanks for your query.
the ultrasound report is absolutely normal, except for the yolk sac as you rightly noticed.
The yolk sac is normally the first structure visible within the gestational sac. A normal yolk sac is round and measures less than 6 mm, between the 5th and 10th week of pregnancy.

Yolk sacs larger than 6 mm are usually indicative of an abnormal pregnancy.
Also, a yolk sac diameter of greater than 5 mm is associated with an increased risk of spontaneous abortion.
However, in 5 % of cases, a large yolk sac ( even upto 8 mm ) has been observed in normal live pregnancies also.

Thus, a large yolk sac is an aberration, not the norm, but not necessarily indicative of abnormality or an impending abortion.
Given its association with poor obstetric outcome, pregnancies with a large yolk sac shold be vigilantly monitored - they require more intensive surveillance compared to other pregnancies with a yolk sac < 6 mm.

As the cardiac activity is normally seen in your case, I would say that there is very less chance that the pregnancy would be abnormal ( specially since the yolk sac is just borderline large, not very large, and some amount of error can occur while measuring it, after all we are talking about 0.4 mm, and you can imagine the margin of error in measuring such a small precision of size ).

The NT scan should be done 5 weeks later, but in your case , I would recommend confirmation of the cardiac activity every week by ultrasound, that will reduce the risk of abortion or any adverse developmental event in the fetus.
Also, please have a thorough NT scan, double marker at 13 weeks, triple marker test / quad test between 16 - 18 weeks and a TIFFA ( targeted imaging for fetal anomalies ) scan at 18 - 20 weeks.

Also, as there is no previous history of miscarriages / abnormal babies, do not worry and stress about the yolk sac right now, which is just 0.4 mm more than the textbook recommendations.
However, there is no harm in being vigilant and watchful.

I congratulate you on your research and observation , even though the doctor did not point out this specific detail.

All the best with your pregnancy and impending parenthood !
Take care, and please feel free to ask for further clarifications.
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