Amniotic Fluid Volume Assessment (500)

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Amniotic fluid volume is an important parameter in the assessment of fetal well being. Oligohydramnios and polyhydramnios are rare. When extremes of amniotic fluid volume are reported this is likely to lead to further investigations and a cascade of interventions.

When assessment of liquor volume is requested the following method of evaluation should be employed

  • Global subjective assessment of amniotic fluid volume as a guide.
  • Formal objective assessment of amniotic fluid by the measurement of a single vertical pool. This must be at least 1cm wide and contain no cord loops.
  • Determine whether normal, oligohydramnios or polyhydramnios as described below. DVP appears to perform better in the assessment of amniotic fluid volume during fetal surveillance since the use of amniotic fluid index increases the rate of diagnosis of olighydramnios and induction of labour without any improvement in perinatal outcome.

NORMAL

Deepest pool between 2 to 8 cms.

OLIGOHYDRAMNIOS

Deepest pool <2cms.

If present the likely underlying diagnosis will be IUGR, PROM/PPROM or renal pathology.

Check fetal kidneys and bladder.

ANHYDRAMNIOS

No liquor.

Likely causes as for oligohydramnios.

POLYHYDRAMNIOS

Global increase in AFV. Deepest pool greater than 8cms.

Assess

  1. Fetal biometry (HC, AC, FL)
    Skeletal dysplasias often associated with polyhydramnios
  2. Fetal anatomy
    Exclude gross fetal abnormality as per department protocol (esp thoracic/neck masses and Congenital Diaphragmatic Hernia CDH)

Look for the fetal stomach

  • The presence of >1 bubble suggests upper gastrointestinal atresia
  • Double bubble suggests duodenal atresia
  • > 2 bubbles jejunal atresia more likely
  • Absent stomach raises possibility of oesophageal atresia
    (90% will have distal fistula and the stomach will be visible)

The stomach may be in the fetal chest secondary to CDH. Check cardiac axis/chest contents

Document on Scan Report: Stomach, Kidneys, Bladder, Nose & Lips and diaphragm seen.

If no clinic appointment within a week refer to Day Care for review.

Editorial Information

Last reviewed: 23/01/2023

Next review date: 31/01/2028

Author(s): Donna Maria Bean.

Version: 2

Approved By: Obstetrics Clinical Governance Group

Document Id: 500

References

Nabhan AF, Abdelmoula YA. Amniotic fluid index versus single deepest vertical pocket as a screening test for preventing adverse pregnancy outcome. Cochrane Database of Systematic Reviews 2008, Issue 3.

Harman CR. Amniotic Fluid abnormalities. Seminars in Perinatology 32:288-294

Magann EF, Morton ML, Nolan TE, Martin JJN, Whitworth NS and Morrison JC. Comparative efficacy of two sonographic measurements for detection of aberrations in the amniotic fluid volume and the effect of amniotic fluid volume on pregnancy outcome. Obstetrics and Gynaecology. 83:959-962