Women often undergo early caesareans or induced labour following detection of decreased amniotic fluid volume, because this is seen as a sign of foetal distress. While no gold standard exists for measuring amniotic volumes, a new Cochrane Systematic Review suggests that the single deepest vertical pocket (SDVP) technique is better than the commonly used amniotic fluid index (AFI) method.
Amniotic fluid protects unborn babies from trauma and infection. A decreased volume may indicate that a pregnancy is at risk. If doctors detect low volumes they often recommend an early delivery. Both AFI and SDVP are assessed using ultrasonography. The AFI is calculated by adding the depths at four different pockets in the amniotic cavity, whereas the SDVP method measures the single deepest pocket.
A team of Cochrane Researchers reviewed data from four trials that together involved 3,125 women. They found that when AFI is used more pregnant women are diagnosed with low fluid volumes than occurs when SDVP is used. There is, however, no indication that AFI is doing a better job of detecting distressed foetuses. As a result, when AFI is used more women will be encouraged to have early deliveries and more women will have a caesarean delivery for the so called 'foetal distress' than are needed than if SDVP was used.
"The problem is having a method that detects foetuses that are in trouble, without including many others that would happily go to term and have a spontaneous onset of delivery, and at the moment it seems that SDVP is the best available option when it comes to measuring amniotic fluid volume," says Asfraf Nabhan, who led the research at the Ain Shams University in Cairo, Egypt.