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Le amniotic liquid is the one in which the fetus evolves throughout the pregnancy. The amount of amniotic fluid in which the unborn baby evolves varies throughout pregnancy.
First secreted by the embryo itself by transudation until about the 23rd week of amenorrhea, amniotic fluid is then produced by the fetus during swallowing and urination (urine). The amniotic fluid is thus perpetually renewed and “filtered” in a way by the urinary system of the fetus.
This fluid reaches its maximum amount around the 36th week of amenorrhea, with about 800 to 1000 mL of fluid, and then decreases slightly until the end.
The amniotic fluid is therefore a good indicator of the proper functioning of the urinary and renal tract of the fetus, and its digestive tract. It is therefore systematically observed during ultrasound monitoring of pregnancy. And its quantity is evaluated using different techniques.
But as with the placenta, for which we sometimes speak of an abnormality of the placenta type “previa” or “accreta”, the amniotic fluid can also have dysfunctions.
Oligoamnios, hydramnios or anamnios: abnormalities in the amount of amniotic fluid
We thus speak ofhydramnios when there is an excessive amount of amniotic fluid,oligoamnios when this liquid is present in too small a quantity, andanamnios when he is totally absent.
All these pathologies of amniotic fluid can compromise pregnancy, but it all depends on the severity of these abnormalities and the stage of pregnancy.
It is the anamnion, the total absence of amniotic fluid, which gives the most unfavorable pregnancy prognosis. Because the fetus needs amniotic fluid to evolve and grow properly in utero, and the absence of this fluid potentially indicates fetal malformations, since the embryo is supposed to produce this fluid on its own. We speak in particular ofpulmonary hypoplasia to suggest insufficient lung development that can be observed in case of anamnios.
Oligoamnios : comment pose-t-on le diagnostic ?
There are several techniques for assessing or measuring the amount of amniotic fluid.
First of all, the gynecologist or the midwife who ensures the follow-up of the pregnancy measures the uterine height using a seamstress meter, as well as the umbilical perimeter. The movements of the fetus observed on ultrasound or the appearance of the uterus may also raise the suspicion of oligoamnios.
The oligoamnios will then be confirmed or not thanks to an ultrasound.
We can then distinguish two types of measures:
- the measurement of the largest cistern (GC), the largest black area around the baby;
- or the so-called four quadrant measurement, which will make it possible to establish the amniotic index (IA).
Obstetrician-gynecologists usually talk about“borderline” or “moderate” oligoamnios if the large cistern is between 1 and 2 cm, or if the amniotic index is between 5 and 8 cm, and“proven” or even “severe” oligoamnios if the large cistern is less than 1 cm, or if the amniotic index is less than 5 cm.
As the amount of amniotic fluid can vary from day to day, and oligoamnion may be transient, these measurements are often repeated over time to confirm and refine the diagnosis of oligoamnion.
Possible causes of oligoamnios
Leakage of amniotic fluid due to premature rupture of membranes (RPM) is the first cause sought in the presence of oligoamnios.
If the pocket of waters does not present any cracks that could explain the oligoamnios, other causes must be explored with the help of adequate examinations:
- a fetal malformation (especially in the urinary or renal system);
- a chromosomal abnormality;
- intrauterine growth retardation (IUGR);
- transfusion-transfused syndrome (TTS);
- an overrun;
- taking medications (nonsteroidal anti-inflammatory drugs or NSAIDs, ACE inhibitors or angiotensin inhibitors);
- high blood pressure in the mother-to-be;
- a maternal-fetal infection (such as cytomegalovirus for example);
- maternal smoking.
Note that, in 30% of cases, no cause to explain oligoamnios is found.
Treatment and management of oligoamnios
The treatment and management of oligoamnios depend on both the cause (s) found and the progress of the pregnancy.
If you have a premature rupture of membranes, the induction of childbirth may for example be an option to consider, if the term of pregnancy is close enough. On the other hand, if the pregnancy is not very advanced, in particular below 17 weeks of amenorrhea, the prognosis is generally unfavorable.
If the lack of amniotic fluid seems occasional, bed rest (rest) and close monitoring can help normalize the situation.
In the event of maternal hypertension, this pathology will be treated and monitored to prevent the oligoamnios from worsening.
In cases where oligoamnios is diagnosed early and / or is accompanied by a fetal malformation or chromosomal abnormality, medical termination of pregnancy (IMG) is suggested. But it is always up to the parents to decide whether or not to terminate the pregnancy.
In very rare cases, another option may be considered. It is an amnio-infusion: an injection into the amniotic fluid of physiological serum, in particular to perform an amniocentesis and an ultrasound to refine the diagnosis.
Oligoamnios: what are the risks for the unborn baby?
The earlier oligoamnios appear in pregnancy, the greater the risk to the unborn baby, since this lack of amniotic fluid can be caused by or lead to fetal malformations. The complications of oligoamnios are also all the more important as it is severe.
Complications for the baby related to oligoamnion itself can be:
- a pulmonary hypoplasia, that is, insufficient lung development;
- un lack of mobility of the fetus can cause limb malformations (clubfoot and hands, joint ankylosis);
- Potter syndrome (facial dysmorphia with flattened nose and back jaw, called retrognatism).
Depending on the progress of the pregnancy and the stage of fetal development, these complications may be reversible, if the oligoamnios disappears.
The other complications of oligoamnios are at the birth level, since it can be treated by an early onset of childbirth, often with a Caesarean to the key.