Amniotic fluid Normal & abnormal Dr. Abdalla H. Alsadig MD

IMPORTANT TOPICS Amniotic fluid function Amniotic fluid function Clinical importance of AF Volume and composition Volume and composition Amniotic fluid abnormalities Amniotic fluid abnormalities

Amniotic fluid function: Allow room for fetal growth, movement and development. Ingestion into GIT→ growth and maturation. Fetal pulmonary development (20 weeks). Protects the fetus from trauma. Maintains temperature. Contains antibacterial activity. Aids dilatation of the cervix during labour.

Clinical importance of AF: Screening for fetal malformation (serum α-fetoprotien). Screening for fetal malformation (serum α-fetoprotien). Assessment of fetal well-being (amniotic fluid index). Assessment of fetal well-being (amniotic fluid index). Assessment of fetal lung maturity (L/S ratio). Assessment of fetal lung maturity (L/S ratio). Diagnosis and follow up of labour. Diagnosis and follow up of labour. Diagnosis of PROM (ferning test). Diagnosis of PROM (ferning test).

Amniotic fluid formation and composition: First & early second trimester : First & early second trimester : Amount is 5-50 ml & arises from: 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 ml 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 volume : About 500 mls enter and leave the amniotic sac each hour. About 500 mls enter and leave the amniotic sac each hour. gradual ↑ up to 36 weeks to around 600 to 1000 ml then↓ after that. gradual ↑ up to 36 weeks to around 600 to 1000 ml then↓ after that. The normal range is wide but the approximate volumes are: The normal range is wide but the approximate volumes are: ml at 18 weeks ml at 18 weeks ml at 34 weeks ml at 34 weeks ml at term ml at term.

Amniotic fluid volume assessment Clinical assessment is unreliable. Clinical assessment is unreliable. Objective assessment depends on U/S to measure: Objective assessment depends on U/S to measure: - deepest vertical pool (DVP). - 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 AFV throughout pregnancy. - 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 AFV throughout pregnancy.

Amniotic fluid abnormalities  Oligohydramnios: Defined as reduced amniotic fluid i.e. amniotic fluid index of 5 cm or less or the deepest vertical pool < 2 cm.  Polyhydramnios: Defined as Defined as excessive amount of amniotic fluid of 2000 ml or more (AFI of > 25 cm or the deepest vertical pool of > 8 cm).

Causes of oligohydramnios: 1. Fetal causes: * Renal cause (57%): * Renal cause (57%): - Renal agenesis (Potter’s syndrome). - Renal agenesis (Potter’s syndrome). - polycystic kidney. - polycystic kidney. - Urethral obstruction (atresia/posterior urethral valve). - Urethral obstruction (atresia/posterior urethral valve). * Fetal growth restriction. * Fetal death. * Postterm pregnancy. * Preterm premature rupture membranes

Causes of oligohydramnios: 2. Maternal causes: Uteroplacental insufficiency. Uteroplacental insufficiency. Preeclampsia. Preeclampsia. 3. Placental causes: twin-twin transfusion. twin-twin transfusion. 4. Drug causes: Prostaglandin synthase inhibitor as NSAID. Prostaglandin synthase inhibitor as NSAID. 5. Idiopathic 5. Idiopathic

Complications of oligohydramnios: In early pregnancy: In early pregnancy: Amniotic adhesions or bands→ amputation/death. Amniotic adhesions or bands→ amputation/death. Pressure deformities (club feet). Pressure deformities (club feet). Pulmonary hypoplasia: Pulmonary hypoplasia: - Thoracic compression. - Thoracic compression. - No breathing movement. - No breathing movement. - No amniotic fluid retain. - No amniotic fluid retain.  Flattened face.  Postural deformities.

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

Oligohydramnios:  Diagnosis: - Fundal > date. - AF I < 5CM, DVP < 2. - IUGR: abdominal circumference < 10 th centile. - Doppler abnormalities - Congenital fetal anomalies.  Management: - Treat the cause (pprom, preeclampsia). - Assess fatal wellbeing (U/S/CTG/Doppler/BPP). - Vesicoamniotic shunting (urethral obstruction). - Amnioinfusion (no↓ in fetal death).

Polyhydramnios

  types 1. Mild hydramnios (80%): a pocket of amniotic fluid measuring 8 to 11 cm. a pocket of amniotic fluid measuring 8 to 11 cm. 2. moderate hydramnios (15%): a pocket of amniotic fluid measuring 12 to 15 cm. 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. a pocket of amniotic fluid measuring 16 cm or more.

Causes of polyhydramnios Fetal malformation: Fetal malformation: - GIT: esophageal/duodenal atresia, tracheoesophageal fistula. - GIT: esophageal/duodenal atresia, tracheoesophageal fistula. - CNS: anencephaly (↓swallowing, exposed meninges, no antidiuretic hormone). - CNS: anencephaly (↓swallowing, exposed meninges, no antidiuretic hormone). Twin-twin transfusion → fetal polyuria. Twin-twin transfusion → fetal polyuria. Hydrops fetalis: congestive heart failure, severe anaemia or hypoproteinemia → placental transudation diabetes mellitus (osmotic diuresis). Idiopathic.

diagnosis of polyhydramnios Symptoms: Symptoms: - dyspnea. - edema. - edema. - abdominal distention - abdominal distention - preterm labour. - preterm labour. Abdominal examination: Abdominal examination: - ↑uterus than expected. - ↑uterus than expected. - difficult to palpate fetal parts. - difficult to palpate fetal parts. - difficult to hear fetal heart sound. - difficult to hear fetal heart sound. - ballotable fetus. - ballotable fetus. Ultrasound: - excessive amniotic fluid. - fetal abnormalities.

management Minor degrees: no treatment. Minor degrees: no treatment. Bed rest, diuretics, water and salt restriction: ineffective. Bed rest, diuretics, water and salt restriction: ineffective. Hospitalization: dyspnea, abdominal pain or difficult ambulation. Hospitalization: dyspnea, abdominal pain or difficult ambulation. Endomethacin therapy:. Endomethacin therapy:. - impairs lung liquid production/enhances absorption. - impairs lung liquid production/enhances absorption. - ↓fluid movement across fetal membranes. - ↓fluid movement across fetal membranes. * complications: premature closure of ductus arteriosus, impairment of renal function, and cerebral vasoconstriction. So not used after 35 weeks * 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. Amniocentesis: to relieve maternal distress and to test for fetal lung maturity. Complications: ruptured membrane, chorioamnionitis, placental abruption, preterm labour.