Episode 164 - All about Polyhydramnios

So a little bit of a mouthful.

As always with these types of episodes, this is just about giving you clear evidence-based information so that hopefully you can feel informed, and you can make decisions that feel right for you and your baby.

So let's start with what polyhydramnios actually is.

Polyhydramnios is the term used when there is more amniotic fluid around your baby than expected for your stage of pregnancy.

So amniotic fluid is the fluid that surrounds your baby in the womb, and it plays a really important role.

It cushions your baby, allows them to move around, supports their lung development, and helps regulate their temperature.

The amount of fluid naturally increases as pregnancy progresses, and then it usually stabilizes or slightly decreases towards the end.

Polyhydramnios is diagnosed when the fluid level goes above what is considered the normal range.

So in the UK, this is typically measured using ultrasound, and there are two main methods.

One is called the amniotic fluid index, often called AFI, where the uterus is divided into four sections, and the deepest pocket in each is measured and added together.

And then the other one is the deepest vertical pocket measurement, which looks at the single largest pocket of fluid.

Generally speaking, polyhydramnios is diagnosed when the AFI is greater than 24 or 25 centimeters or when the deepest vertical pocket measures more than eight centimeters.

Mild polyhydramnios tends to fall just above these thresholds, while moderate and severe cases are higher.

Now, hearing that you have too much fluid can understandably sound quite alarming, but it is really important to stress that most cases of polyhydramnios are mild, and in many cases, there is no clear cause, and outcomes are still very positive.

In terms of how common it is, polyhydramnios affects around 1 to 2% of pregnancies overall, so not hugely common, and the majority of those are mild cases.

Moderate and severe cases are much less common.

So why does polyhydramnios happen? Amniotic fluid is constantly being produced and removed.

So your baby swallows the fluid and then passes urine, and this balance helps regulate the volume.

So anything that affects that balance can potentially lead to an increase in fluid.

In some cases, there is an identifiable cause, and one of the most common associations is gestational diabetes.

So when blood sugar levels are higher, this can lead to increased fetal urine production, which can increase the fluid levels.

Another possible cause is related to the baby's ability to swallow.

Certain conditions that affect swallowing or digestion, such as gastrointestinal blockages, can result in fluid building up.

There can also be associations with fetal conditions, including some chromosomal differences and infections, although these are much less common.

So it's really important to emphasize, in a large portion of cases, especially mild ones, no cause is actually found.