Determining a threshold for amniotic fluid as a predictor of perinatal outcome at term.
OBJECTIVE
To determine a threshold level of amniotic fluid in low-risk term pregnancies predictive of adverse perinatal outcome.


METHODS
Prospective cohort study of low-risk patients at term undergoing amniotic fluid volume measurement. Amniotic fluid index (AFI) remained blinded unless ≤ 1 cm or ≥ 25 cm. Primary outcome was a positive fetal vulnerability index (FVI). The last AFI was evaluated as predictor of a +FVI. We estimated that we needed to perform ultrasounds on 620 women.


RESULTS
Patients were enrolled through 2004-2008. There were 24 (7.8%) patients delivering a neonate with +FVI. An AFI < 8 cm increased the risk of a +FVI (risk ratio 2.70 [95% CI 1.2, 6.0]; p = 0.01); however, the area under the receiver operating characteristics curve was 0.60. Enrollment was stopped at 308 patients due to enrollment challenges.


CONCLUSIONS
An AFI cutoff <8 cm was associated with an increase in FVI outcomes but had a low positive predictive value for a +FVI. Isolated incidentally found low fluid in uncomplicated pregnancies may not be an indication for immediate intervention.
Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Lehigh Valley Health Network, Allentown, PA 18105, USA. joanne_n.quinones@lvhn.org
Joanne N
JN
Quiñones
Anthony O
AO
Odibo
Marilyn
M
Stringer
Meredith L
ML
Rochon
George A
GA
Macones
D000293:Adolescent; D000328:Adult; D000653:Amniotic Fluid / Q000000981:diagnostic imaging / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000175:diagnosis / Q000209:etiology; D007744:Obstetric Labor Complications / Q000175:diagnosis* / Q000209:etiology; D011247:Pregnancy; D011256:Pregnancy Outcome; D011379:Prognosis; D012016:Reference Values; D012189:Retrospective Studies; D047929:Term Birth / Q000502:physiology; D016216:Ultrasonography, Prenatal / Q000592:standards*; D055815:Young Adult