About 5% of pregnancies are diagnosed with hydramnios, or in other words, excess amniotic fluid. The search for the cause is therefore decisive in order to initiate treatment when it is necessary. The explanations with Pr Cyril Huissoud, secretary general of the CNGOF, head of the Obstetric Gynecology Department of Croix-Rousse.
Understanding hydramnios and the role of amniotic fluid
Hydramnios is excess amniotic fluid that manifests as uterine distension in pregnant women. To better understand this phenomenon, let's start by explaining how amniotic fluid is formed and its different functions.
Amniotic fluid is necessary for a baby's development. It creates the space necessary for its growth by allowing it to mobilize to develop its joints and muscles. " The more liquid there is, the more the fetus moves because it has room to make its movements. On the other hand, when the liquid is really present in too much quantity, it can create pressure and hinder its movements. », Observes Professor Cyril Huissoud.
Amniotic fluid is also essential for the development of babies' lungs, but also the digestive tract. " Throughout the pregnancy, the fetus will swallow the amniotic fluid which partly goes to the intestines and lungs », Reports the obstetrician-gynecologist. The amniotic fluid also provides a mechanical protection function for the baby in the event of shock, or even protection against bacteria. It also helps keep the baby at an optimal temperature. Finally, when the water bag is intact before childbirth, it promotes dilation of the cervix.
How is amniotic fluid produced during pregnancy?
In early pregnancy, before 16-17 weeks of amenorrhea, the production of amniotic fluid is carried out through the epidermis of the fetus by transudation. Thereafter, 90% of the fluid is produced by the baby's diuresis (urine production), and the remainder by fluid produced by the lungs (between 5 and 10%) and extremely anecdotally by the membranes. " Around the 6th or 7th month of pregnancy, the volume of amniotic fluid is around 800ml, which roughly corresponds to the daily production of amniotic fluid, since it follows a continuous cycle of production / resorption, on pain of s' accumulate. This balance between production and resorption is quite precarious and any destabilization can lead to an excess or, on the contrary, to a defect of amniotic fluid. », Says the specialist.
How is hydramnios diagnosed?
An ultrasound can be used to diagnose hydramnios, but quantifying amniotic fluid is not always easy. " It can be suspected when the mother has a larger uterus than her gestational age would like. This allows you to subjectively assess the amount of amniotic fluid », Explains Professor Huissoud. The PHELAN index is a benchmark for assessing the amount of amniotic fluid by measuring the large cisterns of the uterus. Between 18 and 25 cm, it is estimated that there is an excess of amniotic fluid, beyond 25 cm, it is diagnosed with hydramnios. And if the measurement exceeds 35 cm, it is considered to be a severe hydramnios. " In this case, the fundal height is so important that it can cause pain, contractions and breathing difficulties because the uterus compresses the diaphragm », Continues our expert.
What are the possible causes of hydramnios?
Amniotic fluid can be found in too much for a number of reasons. " Most of the time, there is no obvious cause, and babies are fine, especially if they are diagnosed with excess amniotic fluid that is not considered hydramnios. But the more important it is, the more we will suspect an underlying cause », Says the doctor.
An important factor is the time in which the size of the uterus increases. If the interval is very quick, it is called acute hydramnios. It is then suspected that something has happened such as fetal anemia, a virus or the mother's production of antibodies to the baby. Conversely, chronic hydramnios takes hold more over the long term. In either case, it should be monitored and managed if necessary, but more urgently if one is facing acute hydramnios.
-Among the other causes, we find gestational diabetes or pre-pregnancy diabetes. " In this case, when the diabetes predates the pregnancy, the hydramnios is often more severe », Notes Professor Huissoud. Because let us remember, from the second trimester, the amniotic fluid is 90% made up of the baby's urine. With diabetes, the fetus will produce a lot more urine.
-We can also find pathologies related to swallowing (neurological origin), knowing that swallowing is necessary to regulate the amount of amniotic fluid. We can also diagnose absorption problems related to digestive malformations such as atresia or compression of the esophagus, or compression of the chest.
-There are specific causes linked to twin pregnancies, especially when babies share the same placenta, and there is a transfusion-transfused syndrome.
-An excess of amniotic fluid can be observed in case of macrosomia (large baby).
-Fetal heart failure, vascular malformation, kidney dysfunction, chromosomal abnormality or metabolic disease may also be the cause of hydramnios.
Additional examinations
Sometimes doctors will offer an amniocentesis. " When we see that this is a big baby with a light hydramnios, we are not very worried. But if the baby is small and bathed in a large amount of amniotic fluid, we will investigate further ”, says Professor Huissoud. Depending on the suspected causes, additional blood tests may also be taken, or serological tests performed to look for possible infection.
Hydramnios: What are the health risks for mother and child?
For the mother, pain may occur, difficulty breathing, as well as edema in acute hydramnios. But most of the time, the pregnant woman does not experience any symptoms.
The main risk for the baby is premature delivery as hydramnios can cause contractions, rupture of membranes, and opening of the cervix. Of course, all the causes inherent in the occurrence of hydramnios can cause more or less significant complications, and affect the health of the fetus, especially if abnormalities and malformations are detected.
What treatments to put in place in hydramnios vas?
If no cause is identified, no treatment will be put in place. If a premature labor is threatened, the mother has difficulty breathing, and acute hydramnios, the doctor may consider amniovidange to lower the pressure. " The problem is that the liquid quickly replenishes behind and that we cannot multiply the use of this gesture », Says our specialist.
Some vascular malformations, especially in the placenta, can be treated in utero. If the fetal heart rate is disturbed, the mother may be given medication to indirectly treat the baby. Finally, if it is diabetes that is the cause of hydramnios, then we will treat the mother and indirectly the baby.