Amniotic fluid disorder

obs/gyn rotation

1. Amniotic fluid disorder Hamad Emad Hamad Dhuhayr

2. Content Amniotic fluid Polyhydramnios Oligohydramnios

3. Amniotic fluid Characters of amniotic fluid : 1) Physical properties : · It is colorless fluid. · Specific gravity : 1010 - 1020. · Reaction : neutral or slightly alkaline ( pH 7-7.5). · Volume : It reaches its maximum volume at 36 weeks (about 1 - 1.5 litre ) and gradually diminishes to be 500-1000 ml at term. It is completely changed every three hours . 2 ) Chemical composition : ·Water : 98-99%. · Solids : 1-2% , half-organic and half-inorganic. Organic constituents include carbohydrates as glucose and fructose, proteins and hormones, the inorganic constituents are similar to those found in the maternal plasma as Na and Cl .

4. Origin of liquor aminii : The amniotic fluid has both fetal and maternal origin. Fetal origin : 1- Fetal urine . 2- Secretion from the amniotic epithelium. 3- Diffusion from the umbilical cord vessels . 4- Transudation through fetal skin . 5- Secretion from bronchial mucosa, buccal mucosa and salivary glands. Maternal origin : The liquor is a filtrate from maternal plasma . Fate of liquor aminii : 1- Fetal : Swallowing. 2- Maternal : Transudation into maternal circulation.

5. Functions of the liquor amnii : During Pregnancy Protection of the fetus. It keeps the fetal temperature constant. 3. It allows free fetal movements . 4 . Prevents adhesions between the amnion and fetal skin. 5. Nutrition. 6. Acts as a medium for fetal excretion . 7. Forms a closed sac around the fetus preventing ascent of infection, from the cervix or vagina . B) During Labour : 1. helps dilatation of the cervix. 2. It prevents direct compression of the placenta between the uterine wall and fetus during uterine contraction thus avoiding fetal asphyxia. 3. When the membranes rupture, the fluid washes the birth canal from above downwards thus removing away any infectious material.

6. 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 AFV throughout pregnancy.

7. Polyhydramnios Definition : It means excessive amniotic fluid, more than 2 liters . By ultrasound the vertical diameter of the largest pocket of amniotic fluid measure 8 cm or more , or the amniotic fluid index (AFI) is 25 cm or more . It can be classified into : 1- Mild : Largest vertical pocket diameter 8 – 11 c.m . 2- Moderate : Largest vertical pocket diameter 12 -15 c.m . 3- Severe : Largest vertical pocket diameter ≥ 16 c.m . Incidence : 1 - 3.5% of all pregnancies.

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

9. Pathology Acute Polyhydramnios : It is very rare , usually occurs in early pregnancy (l6weeks) .and is almost always associated with uniovular twins. A large amount of fluid accumulates in a few days; it leads to abortion or preterm labour . Chronic Polyhydramnios : Commoner than acute. Usually in late pregnancy , the fluid accumulates slowly.

10. 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 . Ultrasound: - excessive amniotic fluid. - fetal abnormalities . - assess fetal wellbeing: BPP & Doppler Fetal karyotyping.

11. Complication I. Maternal : A) During Pregnancy : 1- Abortion (as a result of overdistension of the uterus). 2- Preterm labour . 3- Premature rupture of membranes. 4- Cord prolapse. 5- Placental abruption. 6- Malpresentation . 7- Nonengagement of the presenting part. 8- Pressure symptoms : as dyspnea, palpitation and edema of lower limbs.

12. B) During Labour : 1- Premature rupture of membranes. 2- Prolapse of arm, cord or both. 3- Abruptio placentae due to rapid escape of liquor with premature separation of the placenta. 4- Splanchnic shock occurs if the fluid escapes rapidly, so the pressure exerted by the uterus on the splanchnic vessels drops suddenly leading to pooling of blood in the splanchnic area and shock. 5- Postpartum hemorrhage due to : - Uterine atony due to overdistension of the uterus. - Retained placenta. Prolonged labour . C) During Purperium : The uterus may take a longer time to involute ( subinvolution ).

13. 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 .

14. Oligohydramnios Definition : Diminished amniotic fluid less than 500 ml. By ultrasound the vertical diameter of the largest pocket of amniotic fluid measures 2 cm or less , or the amniotic fluid index is 5 cm or less . Incidence : about 0.5 % of all pregnancies. Time of onset may be : 1- Midgestation (poor prognosis). 2- Third trimester.

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

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

17. Diagnosis Diagnosis : 1- The fundal level is lower than the period of amenorrhea. 2- Breech presentation is common. 3- The fetal parts are easily felt and the fetus is almost immobile. 4- The FHS are clearly heard . Investigation : 1- Ultrasound : Values : · Confirm diagnosis : DVP ≤2 cm or AFI ≤5 cm. · Detect a cause : - Fetal growth restriction. - Congenital anomalies. · Malpresentation . · Assess fetal wellbeing : BPP and Doppler. 2- Evaluation of fetal wellbeing (serial) : DFMC – NST – BPP - Doppler. 3- Fetal karyotyping.

18. 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.

19. Management Treat the cause ( pprom , preeclampsia ). Assess fetal wellbeing ( U/S/CTG/Doppler/BPP ). Vesicoamniotic shunting ( urethral obstruction ). Amnioinfusion (no↓ in fetal death).

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