Contents
The fluid in which the fetus evolves during the nine months of pregnancy is called amniotic fluid. The amount of this fluid varies during pregnancy, from about 20 ml at 7 weeks of gestation, to about 980 ml between 32 and 36 weeks of gestation, and then decreases slightly until term.
First secreted by the embryo itself by transudation, amniotic fluid is then produced by the fetus during swallowing and urination. The amniotic fluid is thus filtered and renewed by the urinary system of the fetus. Fact, it is a good indicator of the proper functioning of the urinary, renal and digestive tracts of the fetus, this is why it is systematically observed during ultrasounds of pregnancy.
If a lack (oligoamnios) or an absence (anamnios) of amniotic fluid can occur, the reverse also exists. We speak of hydramnios when the amniotic fluid is present in too much quantity. Hydramnios is believed to be present in 0,5 to 6% of pregnancies, although estimates differ depending on the source.
Note that doctors generally distinguish chronic hydramnios, which is the most frequent hydramnios, the onset of which is progressive and the onset of late, acute hydramnios, which appears earlier during pregnancy, the progression of which is considerable and the volume large. Chronic hydramnios is more favorable in terms of pregnancy outcome than acute hydramnios, although the latter can be treated urgently.
Hydramnios : comment pose-t-on le diagnostic ?
Several approaches coexist to measure the amount of amniotic fluid, and therefore diagnose hydramnios.
The uterine height measured by the gynecologist or midwife can be a first indication, just like the umbilical height.
Next comes ultrasound, where two types of measurements can be performed:
- 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).
A “normal” amniotic index is between 5 and 24 cm. We usually talk about hydramnios above 24 cm. As for the measurement of the large cistern, it indicates an “excess of liquid” when it is between 8 and 12 cm, and a proven hydramnios when it exceeds 12 cm.
We also speak of “excess amniotic fluid”When it is between 1 and 2 liters, and hydramnios found when the amniotic fluid exceeds 2 liters.
What are the causes of a hydramnios?
The possible causes for the occurrence of hydramnios are varied, but must be methodically identified, the underlying cause can sometimes be treated to overcome the excess amniotic fluid.
There are four main categories concerning the causes of hydramnios:
- fetal causes (40%): malformations (central nervous system, digestive system, lungs, heart, spina bifida…), chromosomal anomaly (in particular trisomy), cervical or sacrococcygeal tumor;
- maternal-fetal causes (20%): gestational diabetes, fetal-maternal blood incompatibility, severe anemias, fetal infections (toxoplasmosis, cytomegalovirus, herpes, syphilis);
- placental and cord-related causes (10%): anomalies of the placenta, transfusion-transfusion syndrome in twin pregnancy, obstacles to the circulation of the cord (knot, torsion, tumor, thrombosis);
- undetermined causes (30%), especially because of a fetus of higher than average weight, which may explain the excess amniotic fluid as a result.
It is understood, in view of these different cases, that numerous examinations can be carried out in order to identify the cause (s) of hydramnios: blood test for diabetes research, amniocentesis for karyotype of the fetus, blood test. Kleihauer-Betke (for fetal-maternal hemorrhage), serological tests in the expectant mother to look for an infection …
Hydramnios: what treatment?
When there is a maternal-fetal cause that can explain the appearance of hydramnios, such as gestational diabetes or an infection, this cause will be treated with a view to treating the hydramnios.
In the case of chronic hydramnios, the treatment consists primarily of increased monitoring of pregnancy, with resting to ensure that it runs smoothly despite this excess liquid.
In critical cases, when there is premature labor, severe symptoms or in the presence of acute hydramnios, it may be considered to reduce the volume of amniotic fluid by performing evacuating punctures. We speak of amnio-reduction or amnio-drainage.
Hydramnios: what complications for pregnancy?
Hydramnios is not without consequences on pregnancy. Here is what it can cause in pregnant women:
- premature contractions or even premature labor, therefore a threat of premature delivery;
- premature rupture of membranes;
- a retroplacental hematoma;
- an abnormal presentation of the fetus during childbirth;
- maternal respiratory disorder;
- umbilical cord procidence;
- uterine atony which prevents scarring of the uterus after childbirth;
- death of the fetus.
These risks and complications of hydramnios are however only indicative, because they depend very much on the degree of accumulation of amniotic fluid, the stage of pregnancy, the underlying cause (s) …
Note also that hydramnios usually does not cause symptoms for the future mother. With severe hydramnios, some pregnant women may experience difficulty breathing or painful contractions at most. Unusual weight gain or leg swelling may also occur.