When a woman is said to have too little amniotic fluid she has oligohydramnios. This is defined as having less than 200 ml of amniotic fluid at term or an AFI of less than 5 cm. This means that during an ultrasound the largest pocket of fluid found did not measure 1 cm or greater at its largest diameter. It is clinically very hard to prove prior to delivery. After the birth, examining the placenta for the presence of amnion nodosum on the placenta is highly correlated with oligohydramnios.
Depending on when the woman is diagnosed with oligohydramnios, there are different complications to look for, although the majority of women diagnosed will not have problems.
In early pregnancy there is the worry of amniotic adhesions causing deformities or constriction of the umbilical cord. There is also concern about pressure deformities, like clubfeet, from not having enough free space in the womb.
Even with oligohydramnios, ultrasound resolution and screening for anomalies is very adequate. So ultrasound is still an effective way to screen for deformities both associated and non-associated with the oligohydramnios.
Later in pregnancy oligohydramnios is one of the signs of fetal distress. This occurrence can cause compression of the cord, which can lead to fetal hypoxia, meaning that the baby is not getting enough oxygen.
Induction is not always the best option when oligohydramnios is present. There are many factors that need to be taken into consideration.
Meconium, if passed cannot be diluted in cases of true oligohydramnios, however, one study found that there were fewer incidences of meconium staining when low amniotic fluid volumes were reported. However, there was an increase in the numbers of babies having fetal distress requiring a cesarean birth.
Other concerns with oligohydramnios:
- Intrauterine Growth Retardation
- Prolonged Rupture of Membranes
- Fetal Malformations (Renal Agenesis, polycystic kidneys, urethral obstruction, etc.)
- Postmaturity Syndrome
Diabetes is commonly thought of as a reason for oligohydramnios, it does not have to cause a problem with the pregnancy with proper treatment.
What treatment options are available for women with oligohydramnios?
Originally we felt that replacing the fluid through amnioinfusion was a great idea. However, this did not appear to be beneficial. We do know that immersion works well at reversing the signs of oligohydramnios.
In the absence of IUGR and fetal anomalies, women diagnosed with oligohydramnios can have an appropriate sized baby with no health problems.