11/14/24, 10\:53 AM Oligohydramnios

Oligohydramnios

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Oligohydramnios\: abnormally low volume of amniotic
Pathophysiology\: Amniotic
decreases near birth; protects fetus and aids organ development.
Causes\: Increased
comorbidities, placental abnormalities, fetal urinary tract anomalies, maternal drug use, post-term pregnancy).
Clinical features\: Diagnosed via ultrasound; may present with
palpate, uterus may appear small for dates.
Investigations\:
Fluid analysis\: Ferning test, Amnisure (PAMG-1), Actim-PROM (IGFBP-1).
Ultrasound\: Maximum vertical pocket (MVP) 2-8 cm, amniotic
Diagnosis\: AFI \<5 cm or MVP \<2 cm on ultrasound.
Management\:
Monitoring\: Serial fetal testing before term (biophysical pro
Intervention\: Possible therapeutic amnioinfusion.
Timing of delivery\: Induction between 36-38 weeks; earlier if co-existing risk factors; conservative management for PROM
before 34 weeks.
Complications\: Poorer prognosis if diagnosed early (\<24 weeks); limb deformities, pulmonary hypoplasia; increased risk of
chorioamnionitis, preterm labour, umbilical cord compression, meconium aspiration, caesarean delivery, non-reassuring
fetal CTG traces.
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A comprehensive topic overview

Introduction

Oligohydramnios refers to an abnormally low volume of amniotic

Aetiology

Pathophysiology
Amniotic
This clear-yellow
Throughout pregnancy, the amount of amniotic
from the fetus’ kidneys/lungs and the removal of
pregnancy to approximately 1000 ml and then decreases as birth approaches.
Amniotic
development of many fetal organs including the lungs, kidneys and gastrointestinal tract.
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Causes of oligohydramnios
Oligohydramnios develops when there is either increased
possible causes, with the most common being rupture of membranes.
Other causes of oligohydramnios include\:
1
Fetal growth restriction
Maternal medical comorbidities (e.g. hypertension)
Placental abnormalities (e.g. abruption)
Fetal urinary tract anomalies (e.g. renal agenesis, posterior urethral valves)
Maternal drug use (e.g. NSAIDs, ACE inhibitors)
Post-term pregnancy

Clinical features

History
Oligohydramnios is diagnosed via ultrasound during routine pregnancy monitoring.
The history can vary depending on the cause and each woman may experience symptoms di
no symptoms at all. If the history includes clear or light pink
be considered.
Clinical examination
During abdominal palpation, fetal parts may be easier to palpate and feel more
addition, the uterus may appear small for dates (e.g. when measuring symphyseal-fundal height).
In the context of suspected rupture of membranes (ROM), a sterile speculum examination should be performed to assess

Diagnosis of ROM can be con
tests that may be performed include a pH test of the
ferning.

Investigations

Fluid analysis
There are a number of investigations that can be used to di
Ferning test\: cervical secretions are placed onto a slide which is then allowed to dry; amniotic
pattern of crystals which can be viewed under the microscope.
Amnisure\: a vaginal swab to screen for the presence of placental alpha microglobulin-1 (PAMG-1) which is found in high
concentration in amniotic
Actim-PROM\: a swab that screens for insulin-like growth factor binding protein-1 (IGFBP-1) which is found in high
concentration in amniotic
Assessment of
Amniotic
In the
The second method calculates the amniotic
then adding together the MVP from each quadrant. A normal AFI is 5 cm to 25 cm.
2

Diagnosis

Oligohydramnios is de
2
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AFI \<5 cm or
MVP \<2 cm

Management

Monitoring
If oligohydramnios is identi
1
fetal demise and emergent delivery. Testing may include biophysical pro
testing.
Intervention
There is some evidence for therapeutic amnioinfusion, where saline or Ringer’s lactate is infused into the amniotic cavity
under ultrasound guidance, but clinical e
3
Timing of delivery
In isolated oligohydramnios, induction of labour should be o4
be considered in cases with co-existing risk factors (e.g. non-reassuring fetal testing, maternal comorbidity).
Earlier delivery may
In preterm rupture of membranes (PROM), conservative management is o
evidence of infection (i.e. chorioamnionitis) or other co-existing risk factors. In patients with otherwise normal antenatal
testing, delivery is recommended at 37 weeks gestation.

Complications

The earlier in pregnancy that oligohydramnios is diagnosed, the poorer the prognosis. If severe and early in onset (i.e. \<24
weeks), mortality rates are as high as 90%.
1
Complications when diagnosed at this gestational age commonly include limb deformities (e.g. muscle contractures,
talipes) due to fetal compression, which may or may not resolve with physiotherapy. Pulmonary hypoplasia may also occur
and is a signi
Other possible complications depend on the cause of oligohydramnios. If PROM occurs, there is an increased risk of
chorioamnionitis and subsequent preterm labour. Oligohydramnios caused by fetal growth restriction or uteroplacental
insu
Additional complications to be aware of during labour include\:
Umbilical cord compression
Meconium aspiration
Caesarean delivery
Non-reassuring fetal CTG traces

References

Payne J. O l i g o h y d r a m n i o s . Published January 2016. Available from\: [LINK]
Lord M, Marino S, Kole M. Amniotic Fluid Index. Published January 2021. Available from\: [LINK]
NICE Clinical Guideline. T h e r a p e u t i c a m n i o i n f u s i o n f o r o l i g o h y d r a m n i o s d u r i n g p r e g n a n c y ( e x c l u d i n g l a b o u r ) . November 2006. Available from\: [LINK]
Published
The American College of Obstetricians and Gynecologists [ACOG]. M e d i c a l l y i n d i c a t e d l a t e- p r e t e r m a n d e a r l y-t e r m
d e l i v e r i e s . July 2021. Available from\: [LINK]
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Reviewer

Maternal-Fetal Medicine Fellow

Related notes

Amniotic Fluid Embolism
Antenatal Screening for Down’s Syndrome
Antepartum Haemorrhage (APH)
Breech Presentation
Caesarean Section

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Contents

Introduction
Aetiology
Clinical features
Investigations
Diagnosis
Management
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