The placenta is also called the afterbirth. It is this that allows your baby to get all its oxygen and nutrients from you. Normally the placenta implants or buries itself into toward the middle or top of the womb. This means that it is well out of the way of the ‘exit’ when it comes to labour, and the baby has an easy passage out. When this doesn’t happen, though, and an ultrasound scan reveals that the placenta has implanted in the lower part of the womb, you are said to have a ‘low lying placenta’. This can potentially cause complications when it comes time to give birth.
How Common is This and How Often Does it Stay Low Lying?
A low-lying placenta is not an uncommon finding on second trimester ultrasound scan. As many as 15% to 20% (one in five to six) of pregnancies have a low lying placenta. Fortunately, only 5% (one in 20) of these remain low lying at 32 weeks and only one third of those are low lying at term (37 weeks). After 28 weeks, a low lying placenta is known as placenta praevia.
The vast majority of pregnant women will have their placenta issues resolved by the time labour starts and will not have any problems.
How Does the Placenta Move?
It doesn’t actually ‘move’ but the growth of the womb and placenta relative to each other mean that it appears to do this.
The lower part of the womb – the lower segment – grows a great deal in mid to late pregnancy. After 28 weeks, its size increases by more than ten-fold. In addition, the placenta grows most toward the top of the womb, where the blood supply is best.
It is because of these two events that most women with a low lying placenta have no problems.
How Will I Know if it Has Moved or Not?
You will be asked to come back for another scan, probably around 32 weeks, by which time most women will be reassured that all is well and the placenta is now positioned toward the top of the womb.
What do I Need to do Now?
If your placenta remains near the bottom of your uterus, then there is nothing you can do to try and encourage the placenta to move.
Unfortunately, because of the placenta’s position over the cervix, there is an increased risk of early labour and bleeding. Very rarely the bleeding can be quite heavy.
If you notice any fresh blood or regular pains, it is important to contact your doctor or delivery suite right away. This is not something that is common.