This blogpost is the summary of the recent TOG article published in January 2026. It provides an overview of polyhydramnios / oligohydramnios; various cause; its impact on mother & fetus and management of pregnancy/delivery. This is an important resource for exam questions.
I hope this blog post is helpful. Feel free to leave your feedback in the comments.
To download the original article (free access) : Click here
To Access ALL TOG articles: Click here
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Introduction
- Amniotic fluid volume (AFV) - vital measurement for fetal well-being
- Amniotic fluid - produced by fetus & comprises fetal urine and lung fluid; protects fetus from trauma, allows fetal movements & prevents cord compression
- Pathologies disrupting swallowing ± urine production or flow can directly affect AFV
- AFV correlated with gestational age & size
- Abnormal AFV could be due to placental, fetal or maternal pathology or a combination
Measuring AFV
- Most accurate method to measure AFV - dye dilution test (limited diagnostic value as it requires amniocentesis)
- Clinically AFV measured in 2 ways - Single Deepest Vertical Pocket (SDVP) or Amniotic Fluid Index (AFI)
- SDVP preferred choice for AFV assessment
- AFI measurement increases rates of oligohydramnios diagnosis
Polyhydramnios
- Defined as - increase AFV, SVDP ≥8 cm or AFI ≥24 cm
- No universal agreed classification
- Complicate 1-2% of pregnancies
- Most common cause of mild-to-moderate polyhydramnios - Idiopathic
- Fetal abnormalities account for over 30% of severe polyhydramnios
- Early severe polyhydramnios or in context of FGR or SGA confers poor prognosis
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| Ref: TOG |
- Most common cause of polyhydramnios - Idiopathic (isolated polyhydramnios)
- Accounts for 60-70% of all cases & 1% of pregnancies overall
- Most cases identified in 3rd tri - mild-to-moderate make up 80% overall & 90% of cases at term’
