1. Amniotic Fluid: The Role in Fetal Health
A/Prof Henry Murray
John Hunter Hospital
University of Newcastle Australia

2. Perceived wisdom Oligohydramnios Hydramnios
Poor placental perfusion → fetal hypoxia → fetal vasoconstriction incl renal arteries → oligohydramnios
Oligohydramnios is a warning of fetal compromise
Hydramnios
Excess urine or interrupted swallowing

3. Daily contribution to amniotic fluid - near term (per 24 hours)
Fetal urine – 1200ml
Fetal lung ml
Oral-nasal secretions 25ml
Transmembranous flows 10ml
Fetal swallowing ml
Intramembranous flow – 400ml
Fetal circulation - Am Fluid interflow
Beall et al Placenta (8-9):

4. Daily contribution to amniotic fluid - near term (per 24 hours)
Fetal urine – 1200ml
Fetal lung ml
Oral-nasal secretions 25ml
Transmembranous flows 10ml
Fetal swallowing ml
Intramembranous flow – 400ml
Fetal circulation - Am Fluid interflow
But what is normal and abnormal volume??

5. Amniotic fluid volume (AFV)
Accurate measure of AFV is by direct measure at operation or dye dilution –
Dieckman et al 1933 Am J Obstet Gynecol, 25:623
Neslen et al 1954 Obstet Gynecol, 3, 598
Charles et al Am J Obstet Gynecol 93:1042
Brace et al 1989 Am J Obstet Gynecol 161:282
Weeks 18 22 28 34 40 42
AFV (mls)
482
630
785
984
836
544
n = 1067+

6. Oligohydramnios - third trimester
By definition - volume < 2.5%ile
2.5%ile at 30 weeks (300 mls)
Brace et al 1989 Am J Obstet Gynecol 161:282
By default definition in 3rd trimester
Less than 300 mls
Accurate prediction by ultrasound 10-15%

7. SONOGRAPHIC ESTIMATIONS OF AMNIOTIC FLUID VOLUME
Technique
Hydramnios
Normal
Borderline
Oligo
hydramnios
Single Deepest pocket
>8
2-8 cm
1-2 cm
<1 cm
Two-diameter pocket
>50 cm2
cm2
   --
< 5 cm2
Amniotic fluid index
>24 cm cm cm
≤5 cm
Larmon et al Obstet Gynecol Clin North Am. 1998
Oligohydramnios:- 0.5 – 5% third trimester
Up to 12% postterm

8. Oligohydramnios
Causes
vary with trimester

9. Oligohydramnios by trimester - what does it mean??
First trimester
Gestational sac diameter – CRL <5mm
Cause unknown – poor prognosis
Second trimester
Fetal anomaly - 51%
PPROM %
Placental abrupt - 7%
IUGR - 5%
Idiopathic - 3% -
Shipp et al, Ultrasound Obstet Gynecol, 1996, 7, 108.

10. Oligohydramnios by Trimester
Third trimester
53% - no obvious cause
? Associated with abnormal aquaporin molecules in placental membranes
28% PPROM/maternal disease/fetal anomaly
19% IUGR/placental insufficiency
Radius trial
Initially low risk women
Zhang et al BJOG

11. Case 1 Mrs S G1 P0 32 weeks Presents with gestational hypertension
BP 130/95, no protein
Blood testing:- normal
Started on Labetalol 100mg TDS

12. Case 1 Mrs S G1 P0 32 weeks Presents with gestational hypertension
BP 130/95, no protein
Blood testing:- normal
Started on Labetalol 100mg TDS
USS normal growth, normal Dopplers
AFI 4.8cms - Oligohydramnios
High risk??

13. Oligohydramnios in 3rd trimester - Does it predict poor outcomes?
No evidence that oligohydramnios in the absence of abnormal Doppler flow indices in the morphologically normal fetus is an indication of significant risk or is an indication for induction or delivery
Magann et al Am J Obstet Gynaecol
Magann et al Am J Obstet Gynaecol
Unterscheider et al Am J Obstet Gynecol

14. ‘Isolated Oligohydramnios’ - a word of warning
1 prospective cohort
AFI ≤ 8cm vs normal AFI at 32 weeks
Increased risk IUGR developing
OR 5.2, 95%CI 1.6 – 22.0
Roberts et al J Perinatal Med
Need to monitor pregnancy
Maternal disease
Placental dysfunction

15. Case 1 Mrs S Remained on Labetalol BP stable Rescanned in 4 days
AFI stable, Dopplers normal
Repeat scanning 3days later AFI 6 – 8cms
Rescanned after 1 week - normal
Delivered at 38 weeks

16. Oligohydramnios Given that isolated oligohydramnios does worry us
Is there anything that we can do other than watch?

17. What can we do??? Cochrane review
Maternal hydration
4 studies, 122 women, 2L oral rehydration
Increase in AFV in normal and low AFI after 2 hours
AFI increase
Oligohydramnios cm 95%CI 1.43 – 2.60
Normal cm 95%CI 2.92 – 6.08
Hofmeyr GJ, etal. Cochrane Database of Systematic Reviews 2002, Issue 1. Art. No.: CD DOI: / CD
NB - Increase not sustained

18. Oligohydramnios in the third trimester - Management
Pregnancy with
AFI ≤ 5.0 at weeks
Assess for
PPROM
Abn Doppler
IUGR
Anomaly
Maternal disease
Fetal compromise Y
Consider admission/steroids/
delivery as appropriate
Are anomalies found? N
Consider maternal
oral rehydration
- Is AFI still ≤ 5.0
Surveillance of
mother and fetus
- rescan 3 days
Deliver if IUGR etc Y N Y
Is AFI 5-8?
Rescan in 7 days N
If AFI > 8, Monitor growth/liquor 2 weekly

19. Oligohydramnios postdates Morris et al BJOG. 2003 Nov;110(11):989-94.
An AFI <5 cm was significantly associated with
birth asphyxia
meconium aspiration,
caesarean section for fetal distress in labour,
a cord arterial pH <7.0 at delivery and
low Apgar scores
Sensitivity of AFI was low at 28.6%, 12% and 11.5% for major adverse outcome, fetal distress in labour or admission to the neonatal unit

20. Oligohydramnios postdates AFI < 5cms
Morbidity from isolated oligohydramnios increases after 41+ weeks
Morris et al BJOG. 2003 Nov;110(11):
Reasonable to induce for low AFI at weeks
Oligohydramnios at 42 weeks associated with significant pathology
Vayssiere et al Eur J Obstet Gynecol Reprod Biol

21. Increased liquor (Hydramnios)
Defined as liquor above 97.5%ile
Single pocket > 8cm or
AFI > 24cm
Mild cms
Moderate 30 – 40 cms
Severe > 40 cms
Polyhydramnios is a clinical definition
Fetal parts not felt

22. Increased liquor
Fetal morbidity and mortality is related to the degree of hydramnios
(AFI > 40cms = 60% neonatal mortality)

23. Case 2 Mrs T G1 P0 Rh neg Now 31 weeks – SHH 39cms
Uncomfortable, polyhydramnios, your USS shows AFI 34cms
She cannot eat, sleep, is dyspnoeic. Not contracting – yet
Normal USS at 18 weeks

24. Causes of anomaly found after 18 week scan
Fetal anomaly of
Swallowing
Micturition
Pressure in fetal chest/right heart

25. Abnormal Fetal Swallowing
Fetal anomaly
Neck
Teratoma, thyroid
Gut atresias
Neurological/muscular abnormalities
Myotonic dystrophy
Aneuploidy

26. Excess Fetal Micturition
Metabolic
Diabetes
Cardiac congestion
TTTS, TRAP
Immune and nonimmune hydrops
Anaemia (haemoglobinopathy, parvovirus, Rh )
CMV, Toxo etc
Renal
Nephrosis

27. Excess pressure in the fetal chest/Right heart
Skeletal dysplasias
Cardiac anomalies
Cardiac arrhythmias
SVT
Chest lesions
CCAM
Pulmonary sequestration etc

28. Causes of anomaly found after 18 week scan
Fetal anomaly
Placental
Haemochorioma
Idiopathic

29. Idiopathic Intramembranous fluid production ? Anomalous fluid channels
60+% transient and resolve before delivery
Commoner in multips
Genetic
Fetal macrosomia (?epigenetics)

30. Excess liquor – Management of Mrs S
Assessment
Full history for ? familial muscular disorder, ? Infection, ? antibodies from transfusion
Tertiary USS as AFI > 30cms
Anomaly, fetal anaemia, congenital infection etc
Aneuploidy assessment esp if IUGR present

31. Excess liquor – Management of Mrs S
Assessment
Full history for ? familial muscular disorder, ? Infection, ? antibodies from transfusion
Tertiary USS as AFI > 30cms
Anomaly, fetal anaemia, congenital infection etc
Aneuploidy assessment esp if IUGR present
Bloods for
Haemoglobinopathy, Group and antibodies, GTT, Infection (Toxoplasmosis, CMV, Parvovirus)

32. Excess liquor – Management
Appropriate intervention to avoid early delivery
Fetal transfusion for anaemia
Karyotype/Counselling for fetal anomaly
Serial Amniorereduction/ nonsteroidals to 33 weeks
If true symptomatic polyhydramnios only
Deliver as close to term as possible with appropriate paediatric presence

33. Hydramnios is high risk - (AFI > 30cms)
Perinatal mortality rate 4x increased
49 per 1000 births vs 14 per (P < .001).
Prematurity, Anomaly,
Asphyxia – poor placental perfusion
Anomaly rate 25x increased
8.4% versus 0.3%; P < .001
Caesarean rate 3x increased
47.0% versus 16.4%; P < .001
Biggio et al Obstet Gynecol 1999;94:773-7

34. Amniotic fluid Window onto fetal health Oligohydramnios and Hydramnios
Nonspecific
Need close investigation

36. Risks - other Risks to mother Risks to fetus
Discomfort, preterm labour, maternal mirror syndrome (esp in fetal hydrops), preeclampsia, respiratory compromise, PPROM +/- abruption,
Labour dystocia, PPH
Risks to fetus
Decreased placental perfusion, prematurity

37. Issues with measurement
Fetal position/movements
Better to use Single deepest pocket/2D pocket
Pressure of transducer
Error
Intraobserver error 11%
Interobserver error 15%
Better to use Amniotic fluid index
NB:- AFI will increase the diagnosis of oligohydramnios compared with SDP (RR 1.7, 95% CI )
Magann et AM J Obstet Gynecol, 1999, 180, 1330)

38. Correlation with AFV
No Ultrasound technique can accurately measure AFV
Is USS assessment of amniotic fluid any use?

39. Isolated Oligohydramnios – is intervention justified?
What do the experts do?
Survey of MFM/perinatologists
92% respondents would induce before 39 weeks
Only 33% believed there would be a better outcome due to the induction
Schwartz et al J Mat Fetal Med

40. Outcomes - High risk pregnancies - AFI ≤ 5
Outcomes - High risk pregnancies - AFI ≤ 5.0cms vs normal (antenatal to 41 weeks)
Metaanalysis Chauhan et al 1999 Am J Obstet Gynecol
18 reports, 10,551 women
Raised LUSCS for FHR anomaly RR 2.2 (1.5 – 3.4)
Apgar < 5min RR 5.2 ( )
pH < ns
Historical comparative study Casey et al Am J Obstet Gynecol
6423 women – 2.3% low AFI
Raised induction - 42 vs 18% (p<0.001)
Stillbirth vs 0.3% (p<0.03)
Abnormal FHR - 48 vs 39% (p<0.03)
NICU - 7 vs 2% (p<0.001)
Neonatal death vs 0.3% (p<0.001)

41. Isolated oligohydramnios
It is clear that isolated oligohydramnios worries us
Can we do anything about it other than induce?

42. Cochrane review Conclusions
‘...may be beneficial in the management of oligohydramnios and the prevention of oligohydramnios during labour or prior to ECV. Controlled trials are needed to assess the clinical benefits....’
Given the lack of evidence that the low AFI is pathological, oral hydration is probably treating the obstetrician not the pregnancy!

43. Oligohydramnios postdates Morris et al BJOG. 2003 Nov;110(11):989-94.
An AFI <5 cm, but not a single deepest pool <2 cm, was significantly associated with
birth asphyxia
meconium aspiration,
caesarean section for fetal distress in labour,
a cord arterial pH <7 at delivery and
low Apgar scores
Sensitivity of AFI was low at 28.6%, 12% and 11.5% for major adverse outcome, fetal distress in labour or admission to the neonatal unit

44. Oligohydramnios postdates Morris et al BJOG. 2003 Nov;110(11):989-94.
Routine use of AFI is likely to lead to increased obstetric intervention without improvement in perinatal outcomes

45. Issues with measurement
Fetal position/movements
Fok et al Ultrasound Obstet Gynecol, 2006, 28, 162
Pressure of transducer
Flack et al Am J Obstet Gynecol, 1994, 171, 218
Error
Intraobserver error 11%
Interobserver error 15%
Brunner et al, Am J Obstet Gynecol, 1993, 168, 1309

46. Amniotic fluid volume vs ultrasound assessment
24 weeks – term
Detection of oligohydramnios
Sensitivity
Specificity
SDP (< 2cm)
0.18
0.68
AFI (≤ 5cm)
0.08
0.71
AFI over diagnosis of oligohydramnios 89%
Dildy et al, 1992, Am J Obstet Gynecol
Magann et al 1994 Obstet Gynecol 83, 959
Chauhan et al 1997 Am J Obstet Gynecol
Magann et al 2004 Am J Obstet Gynecol

47. Isolated Oligohydramnios – is intervention justified?
What do the experts do?
Survey of MFM/perinatologists
92% respondents would induce before 39 weeks
Only 33% believed there would be a better outcome due to the induction
Schwartz et al J Mat Fetal Med

48. Cochrane review Hofmeyer 2002
Conclusions
‘...may be beneficial in the management of oligohydramnios and the prevention of oligohydramnios during labour or prior to ECV. Controlled trials are needed to assess the clinical benefits....’
Given the lack of evidence that the low AFI is pathological, oral hydration is probably treating the obstetrician not the pregnancy!

49. Isolated oligohydramnios
It is clear that isolated oligohydramnios worries us
Can we do anything about it other than induce?

50. Hydramnios is high risk (AFI > 30 mm)
Congenital malformations 44.5%
10.3% of the infants were stillborn,
41% had more than one malformation,
14.5% had a chromosomal abnormality.
290 cases of polyhydramnios in 225,669 consecutive pregnancies
Stoll et al Community Genet 1999;2:36-42)

51. Isolated oligohydramnios - No fetal, maternal or Doppler pathology
Perinatal outcomes
Meta-analysis Rossi et al Eur J Obstet Gynecol Reprod Biol
4 articles
679 low AFI vs 3264 normal AFI
Tendency to increased intervention in low AFI
OR (95%CI – 5.29)
No differences in Meconium, Apgar scores, umbilical cord pH, SGA, NICU or Perinatal Death
Small numbers and did induction save morbidity??

52. Induction in otherwise low risk women
54 women at 40 weeks randomised to induction vs expectant management for AFI ≤ 5cm
No difference in UA pH, Apgar scores, NICU admission
Ek et al, Fetal Diag Ther
All studies have tiny numbers