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Hydramnios, oligoamnios: too much or not enough amniotic fluid?
The amount of amniotic fluid is monitored throughout pregnancy. An excess (hydroamnion) or a decrease in this fluid (oligo-amnion) can indeed be the symptom of a pathology of the unborn baby or of its mother. These abnormalities can also cause uterine contractions and complicate childbirth.
Hydramnios, an excess of amniotic fluid
Definition
Hydramnios is an excessive amount of amniotic fluid compared to the term of pregnancy. The volume of amniotic fluid varies in fact over the months: it gradually increases until it reaches its maximum (800-1000 ml) around 36-38 weeks of amenorrhea before gradually decreasing. Between 1000 and 2000 ml, doctors speak of excess amniotic fluid. Beyond that, it is hydramnios. Its incidence is 0,5 to 2% of pregnancies.
Causes
In about 15% of cases, hydramnios is explained by a maternal pathology, most often gestational diabetes. A maternal-fetal infection (toxoplasmosis, Parvovirus B19, cytomegalovirus) may also be involved.
In about 13% of cases, we find an anomaly of the fetus’s digestive system, a malformation of its nervous system (anencephaly, spina bifida, hydrocephalus, etc.), cardiac pathology, chromosomal abnormalities. So-called biamniotic monochorial twin pregnancies (embryos share a single placenta but each have their own amniotic pouch) are also more at risk.
In 2/3 of the cases, the hydramnios is idiopathic, that is to say without identified cause.
Diagnostic
Sudden weight gain, generalized edema, shortness of breath should lead to a consultation. If the doctor suspects hydramnios during the physical examination (uterus higher than normal), he will do or have an ultrasound done to accurately measure the volume of amniotic fluid to confirm it.
risks
Pressure from too much amniotic fluid can cause membranes to rupture prematurely or cause uterine contractions, increasing the risk of premature labor. Hydroamnios also favors breech presentations (head up) or transverse, which can complicate childbirth.
Supported
The management of hydramnios begins with treating the cause when it has been identified, most often gestational diabetes. If it is a fetal pathology, the mother-to-be is referred to a Multidisciplinary Prenatal Diagnosis Center or a level III maternity hospital.
At the same time, or when no cause has been identified, medical treatment with anti-prostaglandins can be implemented to limit the amount of amniotic fluid. Evacuating punctures can also be performed.
Oligoamnios, a decrease in amniotic fluid
Definition
Oligoamnios is an insufficient amount of amniotic fluid compared to the term of pregnancy. The volume of amniotic fluid varies in fact over the months: it gradually increases until it reaches its maximum (800-1000 ml) around 36-38 weeks of amenorrhea before gradually decreasing. Specialists suggest oligoamnios when the volume is less than 250 ml. Excluding premature rupture of membranes, its incidence is 0,5 to 5-8% of pregnancies.
Causes
The decrease in amniotic fluid is most often due to a cracking of the membranes, or even a premature rupture of the water bag.
It can also be linked to arterial hypertension of the mother-to-be: the placenta ensuring less well the exchanges between the pregnant woman and the fetus, the latter grows little and urinates little, hence the decrease in the volume of amniotic fluid.
Other causes, rarer, can be found such as an abnormality of the urinary tract of the fetus or chromosomal abnormalities.
Diagnostic
The decrease in amniotic fluid is detected during monthly monitoring: when the doctor or midwife palms the belly, the uterine height is lower than normal. An ultrasound then confirms the abnormality.
risks
Depending on the term of the pregnancy, an insufficient amount of amniotic fluid can compromise the proper development of the fetus’ pulmonary system and put its vital prognosis at risk. When it is due to a cracking or rupture of the membranes, it can be synonymous with miscarriage or premature labor.
Supported
The management of oligo-amnion involves the treatment of the cause when it has been identified, most often pregnancy hypertension.
If a cracking of the membranes or a premature rupture of the water bag are at the origin of the oligo-amnion, the management depends on the term of the pregnancy. In all cases, they require absolute rest and close monitoring of a possible infection of the amniotic fluid. Even if it is less systematic than in the past, they can justify inducing childbirth.