What is oligohydramnios?
This is the term for less than expected fluid in the amniotic sac. By 36 weeks, for example, the normal volume is between 800-1000ml. Oligohydramnios is found in around 8% of all pregnancies. Even though in some cases no reason for a reduction in fluid is discovered, it's most commonly caused by a small tear in the amniotic sac, causing a slow leak of fluid, or the waters having broken early.
Sometimes certain medications, such as ACE inhibitors and ibuprofen, can cause reduced amniotic fluid.
There are implications to having too little or too much amniotic fluid (see polyhydramnios). When you have too little, these include the possibility of an abnormality in the unborn baby, especially with the kidneys, as he may be failing to pass ingested fluid back out as urine; dehydration in the mum-to-be; your waters breaking early or a puncture in the amniotic sac going unnoticed; your dates being wrong; or a failing placenta. Also, your baby may be born with a flattened face or club foot (talipes) from having been squashed in the womb.
A failing placenta can sometimes be caused by high blood pressure, lupus, diabetes or pre-eclampsia in the expectant mum. In any case, if you're found to have oligohydramnios, you'll be monitored more closely throughout the rest of your pregnancy. The condition may be discovered during a routine scan or it may be diagnosed by an extra scan after your bump measures smaller than expected at an antenatal check.
What are the symptoms of Oligohydramnios?
Symptoms occur most frequently in late pregnancy or in overdue mothers. There are usually no immediately obvious tell-tale signs a mum-to-be will notice herself, but clinical symptoms include your bump being smaller than expected for dates when measured by your midwife, or a routine scan showing less than expected fluid in the amniotic sac.
Some women report a drop in activity in their unborn babies; and sometimes there's a reduction in foetal heart rate.
What are the treatments and remedies of Oligohydramnios?
Any mum-to-be with oligohydramnios will be monitored closely throughout the rest of pregnancy. If the cause is waters breaking early, this puts both mother and baby at risk of infection, and hospital admission will be necessary.
If a baby is failing to thrive (grow properly), labour is likely to be induced before full term is reached: it's a question of weighing up the comparative risks of continuing with the pregnancy or delivering the baby early. During labour, your baby's heart rate will probably be monitored continuously.
Your doctor may decide that you need to take more fluids on board yourself, either orally or via a drip. Other procedures that may be discussed in severe cases include amnio-infusion, when fluid is injected into the amniotic sac during labour to protect the umbilical cord from becoming compressed.
This guide
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Further help
For health advice and information 24 hours a day, 365 days a year, the NHS offers call and web services. You can also visit NHS websites for services, health information and health news at nhs.uk
- England – call 111 from any landline or mobile phone free of charge, or visit nhs.uk
- Scotland – call 111 from any landline or mobile phone free of charge, or visit nhs24.com
- Wales – call 0845 4647 , or visit nhsdirect.wales.nhs.uk
- Northern Ireland – visit hscni.net