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This is a condition which means there is an inadequate amount of amniotic fluid surrounding the baby in the uterus. This watery compound supports the baby in a number of different ways, and it is important that there is the correct volume i.e. not too much and not too little, so there is no compromise to the baby’s well being.
Early in the pregnancy, amniotic fluid is formed in the amniotic sac. Fluid comes directly from the mother’s circulating fluid volume and helps to support the baby before their kidneys take over this role. From around 20 weeks of gestation, the baby’s kidneys produce urine which is the source of the majority of amniotic fluid.
Amniotic fluid or liquor is generally clear and has a distinctive, almost ammonia type smell. If a baby passes a bowel motion (meconium) whilst still in the uterus, the amniotic fluid changes from being clear to speckled with black fragments or to a greenish colour, caused by the baby’s black meconium.
There are a few ways that the volume of amniotic fluid can be measured. An Amniotic Fluid Index (A.F.I.) can be carried out under ultrasound. This is when the deepest, most unobstructed, vertical fluid level in the uterus is measured.
Oligohydramnios is suspected when there is less than 500mls of amniotic fluid between 32-36 weeks of pregnancy. Though it is important to bear in mind that every pregnancy is unique and a smaller volume of amniotic fluid is not always a cause for concern. It is normal, for example, for the amniotic fluid to reduce in volume as the expected date of confinement (E.D.C.) comes closer. According to The American Pregnancy Association, around 8% of pregnant women can have low levels of amniotic fluid though only 1/2 (4%) of them end up being diagnosed with oligohydramnios.
Mothers with oligohydramnios may not appear as large as they would normally be at their level of gestation. Appearing small and undersize can provide a clue as to whether there is sufficient fluid surrounding the baby. There may also be a change in the level of foetal movements, with a slowing down of activity, particularly of whole body movements. This is because amniotic fluid acts as a buffer to support the somersaults and tumble turns babies do when they are still in utero.
Most commonly in the third or final trimester of pregnancy. When it is diagnosed at the 20 week scan, the cause is usually due to renal (kidney) complications in the baby.
This depends on the stage of pregnancy. Monitoring, abdominal measurement, regular ultrasounds and recording of the baby’s movements are all fairly standard management options. If the volume is very low, then additional fluid in the form of saline, can be infused into the mother’s uterus during her labour to alleviate any potential compression on the umbilical cord. If a mother has been unwell and becomes dehydrated, then infusing her with intravenous fluids helps to restore her circulating fluid volume which in turn, increases the amniotic fluid balance to a safe level.