Description, Causes and Risk Factors:
Presence of an excessive amount of amniotic fluid, usually over 2,000 mL. Amniotic fluid provides the fetus a protective environment suitable for growth and development. Hydramnios is defined as deepest vertical pool of 8 cm or greater or an amniotic fluid index above 95th centile for gestational age. Polyhydramnios occurs in 2% of admitted obstetric cases. It is more common in multigravida. In 50% cases the cause could not be identified. Perinatal mortality occurred in 32% cases.
Causes of polyhydramnios are multifactorial, maternal cause is diabetes mellitus and fetal causes are duodenal atresia, sacrococcygeal teratoma, chorioangioma, twin to twin transfusion syndrome, and chromosomal anomaly. Infections that may affect your baby, such as rubella, cytomegalovirus, toxoplasmosis and syphilis, may be associated with polyhydramnios.
There is increase risk of preterm labor in polyhydramnios. Preterm delivery related to multiple gestation polyhydramnios was associated with enhanced amniotic expression and activity of cyclooxygenase type-2. The babies being delivered near term have better prognosis than the babies of less gestation. These patients require hospital admission.
Some are compatible with life and some are not. One is duodenal atresia with increased risk of prenatal asphyxia and death, even when the karyotype is normal and no associated anomalies are present. Death could be caused by vagal over activity due to distention of the upper gastrointestinal tract.
In past few years polyhydramnios has been extensively studied and it has been found that in majority of the cases the fetus is normal and there is no causative factor in the mother as well. Prognosis for such pregnancies is good.
Now-a-days intrauterine status of the fetus can be readily and confidently assessed by using a wide range of diagnostic facilities including ultrasound examination, Doppler study, echocardiography, amniocentesis, cordocentesis to check fetal chromosomal pattern and serological studies. With better facilities for detailed investigations of the mother and the fetus, more causative factors can be identified and this helps in the counseling of the parents regarding etiology of polyhydramnios, fetal prognosis, recurrence risks and different management options for the baby if it needs surgical or medical care after birth.
In older studies the incidence of polyhydramnios was 3.5% but more recent studies give an incidence of 0.2% due to earlier diagnosis and better management of pregnancies with fetal congenital abnormalities.
Polyhydramnios usually starts from about the thirtieth week of pregnancy. You may feel that your tummy is getting too large too quickly and that your skin is stretched and shiny. You might feel so breathless that it is hard to climb a flight of stairs.
Other symptoms include abdominal pain, severe heartburn and constipation, swollen legs and varicose veins. When the doctor carries out an examination, you will appear to be 'large for dates'. They may find it difficult to feel the baby or hear his heartbeat because there is so much fluid round him. Ultrasound scanning can confirm the diagnosis of polyhydramnios
Polyhydramnios is an uncommon complicationassociated with pregnancy. Such pregnancies are highrisk pregnancies and need to be thoroughly investigated.The clinical problems associated with polyhydramnios,apart from fetal anomaly, are maternal discomfort,difficult clinical examination of fetus and premature labor. Experienced operators can detect polyhydramnios subjectively.
A quantitative approach can be taken by dividing the uterine cavity into four quadrants or pockets. The largest vertical pocket is measured in centimeters and the total volume is calculated by multiplying this level by 4. This is known as the amniotic fluid index (AFI). Polyhydramnios is defined as an AFI of more than 24 cm or a single pocket of fluid of at least 8 cm deep that results in a total fluid volume of more than 2,000 mL.
AFI is one of the five component scores of a biophysical profile (a non-invasive test that detects the presence or absence of fetal asphyxia). The other components are fetal breathing movements, gross body movements, fetal tone and fetal heart monitoring.8
Enhanced modalities with the inclusion of color Doppler techniques may be required if differentiation is needed from chorioangioma.
The following may be helpful in excluding associated diseases:
U&Es (urea and electrolytes) and urine osmolality if diabetes insipidus is suspected.
If hydrops fetalis (excessive fluid in one or more fetal compartment - e.g. the pleural or abdominal space,common in rhesus hemolytic disease) is present the following may also be appropriate:
Screening for cytomegalovirus, syphilis, rubella, toxoplasmosis, parvovirus 19.
Screening for maternal antibodies against fetal red blood cells.
If you are not known to have diabetes, you will be given a glucose tolerance test to check your blood sugar levels. If these are high, you may be referred to a specialist who can get your blood sugar levels down. This will reduce the amount of fluid. Ultrasound scanning can help spot any problems with your baby.
Mild polyhydramnios can be simply monitored and treated conservatively.
Preterm labour is common due to overdistension of the uterus, and measures should be taken to minimize this complication. This includes regular antenatal checks and inspection of the uterus and bedrest towards the latter stages.
Intramuscular steroids should be given to the mother antenatally if preterm deliver is considered. This helps to improve lung maturity.
Serial ultrasound scans should be carried out to monitor the AFI and monitor fetal growth.
Fetal hydrops anemia should be treated with erythrocyte transfusion, either intravascularly or via the fetal abdomen. This reduces the likelihood of fetal congestive failure, thereby allowing prolongation of the pregnancy and improving survival.
If gestational diabetes is diagnosed, tight glycemic control should be maintained. This is usually done with dietary manipulation and insulin is rarely needed.
Indometacin is the drug of choice for the medical treatment of polyhydramnios. It is very effective, particularly in cases where the condition is related to increasing fetal urine production. The mechanism of action appears to be an effect on urine production by the fetal kidney, possibly by enhancing the effect of vasopressin. It is not effective in cases where the underlying cause is neuromuscular disease affecting fetal swallowing, or hydrocephalus. It is contra-indicated in twin-to-twin syndrome or after 35 weeks, as adverse effects outweigh benefits in these cases.
Amniocentesis is recommended in cases where Indometacin is contra-indicated, in severe polyhydramnios, or in patients who are symptomatic. It is contra-indicated in premature rupture or detachment of the placenta, or chorioamnionitis (inflammation of the chorioamniotic membranes and fluid - usually infective).
Induction of labour should be considered if fetal distress develops. Beyond 35 weeks it may be safer to deliver anyway. Induction by artificial rupture of the membranes (ARM) should be controlled, performed by an obstetrician and with consent to proceed to lower segment Caesarean section if required.
Polyhydramnios associated with twin-to-twin syndrome may benefit from laser ablation of the connecting placental vessels.1
The first step is to identify if there is an underlying cause.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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