Placental Issues Flashcards
What is the definition of oligohydramnios?
- Decreased amniotic fluid volume surrounding the fetus for gestational age
- Can adversely affect fetal development
This is too little amniotic fluid. The normal range is 400-1500 ml.
It is defined clinically as the absence of fluid surrounding the fetus. On ultrasound scanning it is defined as a pool depth of amniotic fluid of less than 2 cm - the normal range is from 2 to 10cm.
What is the aetiology of oligohydramnios?
- reduced production of amniotic fluid
failing placental function
bilateral renal agenesis
posterior urethral valves - increased losses of amniotic fluid, as in prolonged rupture of membranes
It is common in pregnancies which have progressed many weeks beyond term.
What are the causes of oligohydramnios?
Caused by amniotic fluid production and movement imbalance
- Dec placental blood flow, Dec fetal urine production, inc amniotic fluid loss > Dec amniotic fluid volume
- Dec fluid cushioning effect > Inc umbilical cord compression risk
- Restricted fetal movement > Dec msk development
- Foetal thorax compression > Dec pulmonary development
- Dec amniotic fluid bacteriostatic effect > Inc infection risk
What are the maternal RFs for oligohydramnios?
- HT disorders
- Diabetes
- Pre eclampsia
- Abnormal placentation
- Premature rupture of membranes (PROM), amniotic fluid leak > fluid loss
- ACEi + ARBs
- NSAIDs
- Post term pregnancy
What are the fetal RFs for oligohydramnios?
- Renal/urinary tract anomalies (e.g. renal agenesis) restricted growth, fetal death > Dec fetal urine production
- Congenital anomalies (Aneuploidy, cardiac, preferential perfusion to brain at kidney’s expense)
Complications of oligohydramnios?
- Amniotic Band syndrome
- Limb position defects
- Pulmonary hypoplasia > Resp distress
- Potter syndrome
- Pulmonary hypoplasia
- Chorioamnionitis
- Low birth weight
- Meconium aspiration syndrome (MAS)
- the foetus has little room to move; as a result, an early breech presentation is more likely to deliver as a breech.
- limb deformities are more common, including talipes and ankylosis of joints
- amniotic adhesions may constrict a limb
What are the S + S for oligohydramnios?
- Uterine size/ fundal height less than expected gestational age
- Easily palpated fetus
- Dec fetal movement
What are the investigations for oligohydramnios?
- investigation of placental function
- ultrasound examination of the foetal kidneys and urogenital system
Uterine US: - Dec amniotic fluid index
- Amniotic fluid measurement in deepest pocket in each uterine quadrant
- Sum of each maximum vertical pocket = AFI
Fetal US + biophysical profile
What is polyhydramnios?
Polyhydramnios is a condition where there is too much amniotic fluid. The normal range is 400-1500 ml with an average of 800 ml.
On clinical examination, only volumes in excess of 2000 ml are reliably detected.
What is polyhydramnios empirically defined by?
Empirically, polyhydramnios is defined as the presence of amniotic fluid pool depth of greater than 10 cm on an ultrasound scan (the normal is from 2 to 10 cm).
What is the aetiology of polyhydramnios?
- aneuploidy is present in 10% of fetuses with sonographic - anomalies and in 1% when the - ultrasound examination is considered to be normal
in persistent polyhydramnios, the prevalence of aneuploidy is increased (10-20%) compared with polyhydramnios with spontaneous resolution
other major causes of polyhydramnios include maternal diabetes, isoimmunisation disease, congenital abnormalities and multiple gestations
What is unexplained polyhydramnios and what is it associated with?
In a large number of pregnancies, the polyhydramnios remain unexplained despite extensive prenatal assessment
malpresentation, macrosomia, primary caesarean delivery and an increased rate of perinatal mortality
When is polyhydramnios usually detected?
30 weeks - most cases results in chronic polyhydramnios
How do we get acute polyhydramnios?
Rarely the amniotic fluid accumulates rapidly, resulting in acute polyhydramnios. There is an increased risk of premature labour before 28 weeks, and it tends to develop earlier than the chronic form, possibly by the 16th to 20th week.
What are the foetal causes of polyhydramnios?
- twin pregnancy, especially uniovular twins
- anencephaly interferes with foetal swallowing
- oesophageal or duodenal atresia prevents foetal swallowing
- spina bifida
- chorioangioma of the placenta
hydrops foetalis - GI anomalies
- High cardiac output state
- Aneuploidy
- Trisomy 18 or 21
- Nonimmune hydrops
