So—you just had your 20 week or so ultrasound and have been told that you have a “low-lying” placenta.
First off—relax–this is usually not a problem at all. Unless that placenta COVERS the opening, it is not going to get in the way at time of delivery.
We do ultrasounds (U/S), in two ways–by putting jelly over the belly –ABDOMINAL U/S ( AUS ),
or vaginally with a slender probe (transvaginal ultrasound, or TVUS)—use your imagination here folks—no pictures!!
At the ultrasound you get when you are 19-23 weeks, unless the placenta touches the internal opening, then there is VERY UNLIKELY to be any issue at all, and repeat U/S is not required. Now–there is a 7 % chance that a placenta previa can be missed with AUS. So if we get an “all clear ” you are good to go. Sometimes the AUS will be “unclear”. This can happen if the placenta is in the back of the uterus–it makes it harder to see. It can happen if you are fluffy–the U/S can only see so deep. It can happen if the baby gets in the way of the picture. When we get an “unclear if touching the internal opening (we call it internal os”), then we can arrange for a TVUS–up the hoohah!! TVUS is about 99% accurate for seeing how close the placenta is to the opening of the uterus (womb).
Now–you can see that IF the placenta is really across the opening to your womb–you are going to have a problem!
With the regular U/S, you are looking at only about 5% need to get TVUS, and 98% of those will rule out a placenta previa. Really about 3 in a thousand will end up with a previa.
SO–IF YOU ARE A PREVIA FOR REAL, you will likely be advised to stop sex–although no studies on this–and who wants to do THAT study–“Well we don’t know if you’ll bleed like stink with sex–how about you 50% try it, and you 50% don’t. If you bleed badly, then you may end up with a premature baby and blood transfusions etc”.
NOBODY is going to agree to that study!
So, now that you know you are a previa, you have to think about delivery–and it will be by C. Section for sure! There are things that even a previa can do to make things even more difficult.
You MAY get an MRI later in the pregnancy (like about 32 weeks), to see if the placenta has actually grown Into the wall of the womb. This is called PLACENTA INCRETA. Very rarely, the placenta can grow right through the wall of the uterus, and this is called a PERCRETA. Either of these can mean you are at high risk for losing your uterus at time of C. Section, because the bleeding can be REALLY HEAVY!! We prefer you live to raise your child!
Sometimes if we anticipate really difficult case–like you are really fluffy or have other medical problems or you don’t agree to blood transfusion, we would prefer you deliver in a big teaching hospital where all the bells and whistles are moments away. If you are a placenta increta or percreta you may need transfer to a bigger hospital.