AMNIOTIC FLUIDFahad zakwan

Amniotic fluid formation and composition:

First & early second trimester:

• Amount is 5-50 ml & arises from:• ultrafiltrate of Maternal plasma through the vascularized

uterine decidua (in early pregnancy).• Transudation of fetal plasma through the fetal skin &

umbilical cord (up to 20 weeks' gestation).

* It is iso-osmolar with fetal & maternal plasma, though it is devoid of proteins.

Volume and composition• From 20 weeks up to term (mainly fetal urine):

• At 18th week, the fetus voids 7-14ml/day; at term fetal kidneys secretes 600-700ml of urine/day into AF.

• Fetal respiratory tract secretes 250ml/day into AF.• Fluid transfers across the placenta.• Fetal oro-nasal secretions.

• Secretion is controlled by:

- Fetal swallowing at term removes 500ml/day.

- Reabsorption into maternal plasma (osmotic gradient).

• AF constituents:

- urea, creatinine & uric acid + desquamated fetal cells, vernix, lanugo hair & others→ hypo-osmolar amniotic fluid….

Amniotic fluid circulation

Amniotic fluid volume :• About 500mls enter and leave the amniotic sac each hour.• gradual ↑ up to 36 weeks to around 600 to 1000 ml

then↓ after that.• The normal range is wide but the approximate volumes

are:

- 500 ml at 18 weeks- 800 ml at 34 weeks.- 600 ml at term.

Amniotic fluid function:1. Allow room for fetal growth, movement and development.

2. Ingestion into GIT→ growth and maturation.

3. Fetal pulmonary development (20 weeks).

4. Protects the fetus from trauma.

5. Maintains temperature.

6. Contains antibacterial activity.

7. Aids dilatation of the cervix during labour.

Clinical importance of AF:1. Screening for fetal malformation (serum α-

fetoprotien).

2. Assessment of fetal well-being (amniotic fluid index).

3. Assessment of fetal lung maturity (L/S ratio).

4. Diagnosis and follow up of labour.

5. Diagnosis of PROM (ferning test).

Amniotic fluid volume assessment

•Clinical assessment is unreliable.•Objective assessment depends on U/S to measure:- deepest vertical pool (DVP).- Amniotic fluid index (AFI). • It is a total of the DVPs in each four quadrants of

the uterus. it is a more sensitive indicator of AFVthroughout pregnancy.

Amniotic fluid abnormalities

Oligohydramnios:

Defined as reduced amniotic fluid of 200ml or less i.e. amniotic fluid index of 5 cm or less or the deepest vertical pool < 2 cm.

Polyhydramnios:

Defined as excessive amount of amniotic fluid of 2000ml or more (AFI of > 25 cm or the deepest vertical pool of > 8 cm) .

POLYHYDROMNIOUS

Polyhydramnios

types

1. Mild hydramnios (80%):

a pocket of amniotic fluid measuring 8 to 11 cm.

2. moderate hydramnios (15%):

a pocket of amniotic fluid measuring 12 to 15 cm.

3. Severe hydramnios (5%) - twin-twin transfusion syndrome :

a pocket of amniotic fluid measuring 16 cm or more.

ETIOLOGY OF POLYHYDRAMNIOS

1. Idiopathic

2. Fetal Anomalies

3. Diabetes

4. Multifetal gestation

5. Immune/Non-immune hydrops

6. Fetal infection

7. Placental haemangiomas

Fetal Anomalies

•Problems with swallowing and GI absorption

• Increased transudation of fluid:• anencephaly, spina bifida

• Increased urination: anencephaly (lack of ADH, stimulation of urination centers)

•Decreased inspiration

SYMPTOMS

1. Dyspnea

2. Abdominal pain

3. Venous stasis

4. Contractions preterm labor

5. Decreased Perception of Fetal Movements

diagnosis of polyhydramnios

•Symptoms:- dyspnea.- edema.- abdominal distention- preterm labour.• Abdominal examination:- ↑uterus than expected.- difficult to palpate fetal parts.- difficult to hear fetal heart sound.

- ballotable fetus.- Decreased fetal mov’t

•Ultrasound:

- excessive amniotic fluid.

- fetal abnormalities.

COMPLICATIONS(fetus)?• Fetal prognosis worsens with more severe

hydramnios and congenital anomalies

• 15-20% fetal malformations

• Preterm delivery

• Suspect diabetes

• Prolapse of cord

• Abruption

(Mother)?

• Dyspnea

• Venous Stasis

• Placental abruption

• Uterine atony

• PPH

• Abnormal presentation -- C/S

TREATMENT

•Mild to Moderate hydramnios: rarely requires treatment

•Hospitalization, bed rest

•Amniocentesis

•NSAIDs

•Blood sugar control

OLIGOHYDRAMNIOS

DEFINITION

reduced amniotic fluid <200mls i.e. amniotic fluid index of 5 cm or less or the deepest vertical pool < 2 cm.

AETIOLOGYFETAL• PROM (50%)

• CHROMOSOMAL ANOMALIES

• CONGENITAL ANOMALIES

• IUGR

• IUFD

• POSTTERM PREGNANCY

MATERNAL• PREECLAMPSIA

• APLA SYNDROME

• CHRONIC HT

PLACENTAL• CHRONIC ABRUPTION

• TTTS

• CVS

DRUGS• PG SYNTHETASE INHIBITORS

• ACE INHIBITORS

IDIOPATHIC

Complications of oligohydramnios:

In early pregnancy:• Amniotic adhesions or bands→ amputation/death.

• Pressure deformities (club feet).

• Pulmonary hypoplasia:

- Thoracic compression.

- No breathing movement.

- No amniotic fluid retain.

Flattened face.

Postural deformities.

In late pregnancy:•Fetal growth restriction.•Placental abruption.•Preterm labour.•Fetal distress.•Fetal death.•Meconium aspiration.•Labour induction/CS.

• Extremely poor fetal prognosis, especially in early pregnancy•Adhesions between amnion and fetal parts ---malformations and amputations•Musculoskeletal deformities•Pulmonary hypoplasia• Cord Compression -- >fetal hypoxia• Passage of meconium into low AF volume: thick

particulate suspension -->respiratory compromise

management• Minor degrees: no treatment.

• Bed rest, diuretics, water and salt restriction: ineffective.

• Hospitalization: dyspnea, abdominal pain or difficult ambulation.

• Endomethacin therapy: .

- impairs lung liquid production/enhances absorption.

- ↓fluid movement across fetal membranes.

* complications: premature closure of ductus arteriosus, impairment of renal function, and cerebral vasoconstriction. So not used after 35 weeks

• Amniocentesis: to relieve maternal distress and to test for fetal lung maturity. Complications: ruptured membrane, chorioamnionitis, placental abruption, preterm labour.

Dr Mona Shroff www.obgyntoday.info

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TREATMENT• ADEQUATE REST – decreases dehydration

• HYDRATION – Oral/IV Hypotonic fluids(2 Lit/d)

temporary increase

helpful during labour,

• SERIAL USG – Monitor growth, AFI, BPP

• INDUCTION OF LABOUR/ LSCS

Lung maturity attained

Lethal malformation

Fetal jeopardy

Severe IUGR

Severe oligohydramnios

• AMNIOINFUSION

• AMNIOINFUSION

INDICATIONS

1.Diagnostic

2.Prophylactic

3.Therapeutic

• Decreases cord compression

• Dilutes meconium