[Is uterine height able to diagnose amniotic fluid volume deviations?]

Abstract

Purpose: To evaluate the performance of a Brazilian reference curve of fundal height (FH) regarding its capacity of screening the deviations of volume of amniotic fluid using a Brazilian reference curve of amniotic fluid index (AFI) as gold standard.

Methods: This was a cross-sectional study evaluating 753 pregnant women receiving prenatal care at the public health services of João Pessoa (PB), from March to October 2006, who had a routine ultrasound exam scheduled for after 26 weeks of gestational age. Cases with diagnoses of twin pregnancy, intrauterine fetal death and major fetal malformations were excluded. Besides socio-demographic information, data regarding fundal height measured in a standard way, estimated fetal weight, AFI and gestational age at the time of the ultrasound exam were also collected. The capacity of the FH curve to predict deviations of the amniotic fluid volume was assessed using the Brazilian curve of AFI according to gestational age as the gold standard. For this purpose, sensitivity, specificity, positive and negative predictive values were estimated for different cut-off points.

Results: The measurement of FH identified 10.5% of women as having low FH possibly associated with oligohydramnios and 25.2% as having high FH possibly associated with polyhydramnios. Using a Brazilian reference curve of AFI, the FH was able to poorly predict the occurrence of oligohydramnios (sensitivity ranging from 37 to 28%) and to reasonably predict the occurrence of polyhydramnios (sensitivity ranging from 88 to 69%).

Conclusions: The measurement of fundal height showed a poor performance for predicting oligohydramnios and a reasonable performance for predicting polyhydramnios. Its use for this purpose is then only supported in settings where the ultrasound exam is not easily or routinely available in order to help define priorities for cases that should have this exam performed.