Around one pregnancy in 100 will be given a diagnosis of polyhydramnios, or too much amniotic fluid.
The average amount of fluid in the uterus is about one litre (which is 2.11 US pints).
Too much fluid is considered to be over 2 litres.
Around 95% of cases are considered mild polyhydramnios (less than 3 litres).
Most women with polyhydramnios have it mildly, but it can still be worrying to be told there are risks associated with too much amniotic fluid.
It can help to understand the causes of polyhydramnios and how it can be treated, so you can be reassured about making the best decision for you and your baby.
What Causes Too Much Amniotic Fluid (Polyhydramnios)?
At least half the time, we don’t know what causes polyhydramnios.
The rest of the time, there is usually one of the following reasons for the condition to develop:
- Diabetes, which causes fetal hyperglycemia and resulting polyuria (fetal urine is a major source of amniotic fluid)
- Problems with baby’s heart rate
- Birth defects which affect baby’s ability to swallow or kidney function, both regulate the amount of fluid in the uterus
- Rh factor incompatibility, which is a mismatch between the mother’s and baby’s blood
- Twin-to-twin transfusion syndrome (TTTS), which is when one identical twin has too much blood flow and the other has too little
- Infections involving the baby
What Are The Risks Of Polyhydramnios?
The main concern for women who have polyhydramnios is the increased likelihood of the following:
- Premature rupture of membranes
- Increased risk of interventions due to baby not being in the optimal position for birth
- Cord prolapse
- Increased risk of severe bleeding after birth
Preterm labour and birth causes significant problems for babies, including lung immaturity, respiratory distress, infections, immature digestive system, heart problems, and long term problems such as cerebral palsy, vision and hearing issues, and poor growth.
How Do I Know If I Have Polyhydramnios?
Care providers may suspect you have more fluid than normal if you are consistently measuring ‘ahead of dates’.
Most women don’t have any symptoms of polyhydramnios, although some may experience pain in their belly and possibly difficulty breathing. This can happen if excessive fluid is causing the uterus to press on organs and lungs.
If polyhydramnios is suspected, you will be sent for an ultrasound to measure the fluid levels. There are two ways to measure amniotic fluid:
- Amniotic fluid index (AFI) which checks how deep the fluid is in four areas of your uterus then the amounts are added up. The normal range for the AFI is 5-25 cms (1.97 inches to 9.84 inches).
- Single or deepest vertical pocket which measures the largest visible area of the uterus and checks the fluid level. The normal range for maximum pool is 2-8 cms (0.79 inches to 3.15 inches).
What Happens If The Levels Are High?
If an ultrasound shows there is a lot of amniotic fluid, you may be told you have polyhydramnios.
It’s important to discuss with your care provider the measurements taken and whether you are in or outside the normal range.
Even if you are on the high end of normal, you are still within the normal range and shouldn’t be given a diagnosis of polyhydramnios unless further testing shows the amniotic fluid has increased.
Your care provider may be concerned you will develop polyhydramnios, but at this point you are in the 50% of women who have more amniotic fluid than normal. It’s possible for amniotic fluid levels to correct, and if you and your baby are healthy and close to full term, it’s likely your care provider will take a wait and see approach.
If your levels are almost within or are in the range of polyhydramnios, your care provider will suggest further testing to see if a cause can be found:
- Blood test to check for diabetes
- Ultrasound to check for birth defects and TTTS if you are pregnant with twins
- Amniocentesis which can check for birth defects
Discuss your levels with your care provider and whether further testing will be likely to benefit your situation or not. Understanding the risks and benefits of all your options is important to ensure you make the best decision for your care.
Can Polyhydramnios Be Treated?
Treatment of polyhydramnios will depend on what is causing the higher levels of fluids, how close you are to full term, and if your baby is healthy.
Drainage of excessive fluid can be performed as an amniocentesis. This may have to be repeated several times and carries the risk of preterm labour, placental abruption and premature rupture of the membranes.
You may be prescribed an oral medication (indomethacin) which reduces the amount of urine your baby produces. This medication is not recommended for use beyond 31 weeks pregnancy and has a risk of causing fetal heart problems.
Side effects of the medication include nausea, vomiting, acid reflux and gastritis (inflammation of the lining of the stomach).
Before accepting any pharmaceutical drugs or preparations (pregnant or not), it’s wise to ask for the product insert, so you can be fully informed of any side effects of any medications or drugs you are given. It’s a much better option rather than being told the risks or side effects are minimal, or “it can cause [insert here], but it doesn’t happen often”. Doctors are not always up to date on drug information, and pharmacists can be a better source if you’re concerned or want a second opinion.
What Happens After Treatment?
If you decide to have treatment your care provider will want to monitor the amniotic fluid levels every 1-3 weeks, to ensure it doesn’t increase.
If the polyhydramnios is considered mild to moderate (a gradual build up during the second half of pregnancy) then it’s likely you will be able to carry your baby to full term. It’s not unusual for mild polyhydramnios to resolve without treatment.
Severe polyhydramnios can mean there is around three times the normal amount of amniotic fluid present.
If your symptoms are increasing and you are close enough to full term (or if your baby isn’t coping), your care provider is likely to recommend an induction of labour. This usually involves breaking your waters in hospital, to ensure you have access to medical assistance should complications such as cord prolapse or placental abruption occur.
Being told you have more amniotic fluid than normal can be frightening. Talk to your care provider about your options and ensure you are well informed about your options for making decisions for management and treatment.