Placenta Covering Internal OS

Jane Foley's picture


Dear Ms Ultrasound,
I am in Delhi, India. My 11 week ultrasound report says that the "placenta is on posterior wall and just covering internal os." What does that mean?

My doctor has asked me to go for the second ultrasound during weeks 16 to 20 and then one in the 7th month. Is there any requirement to go for three ultrasounds in a pregnancy?

With regards,


Hello Anjana,
Your pregnancy is not at all worrisome yet. Diagnosing a low lying placenta at 11 weeks is too early. The placenta is not completely formed yet.It is proper to have you come back into the second trimester to be rescanned. Officially you cannot diagnose a placenta previa (low lying placenta that is near or covering the cervix) until the third trimester. All they will be doing is monitoring you. If at the second ultrasound the placenta completely covers the os (and odds are it won't) you will most probably be put on bed rest.

Then you will have your third ultrasound to see if the placenta has moved away from the os.

Usually as the pregnancy grows, the placenta moves up with the wall of the uterus, away from the internal os. I have a strong suspicion your next ultrasound will be normal.

Don't worry about having more ultrasounds. They are not harmful in any way and are lots of fun.

Thanks for writing, I always love getting questions from other parts of the world.

-- Jane, RDMS