Introduction
Hydrothorax is a rare disease of the fetus. Although the outbreak in the community is unclear, its prevalence in treatment centers at level 3 is reported to be about one in every 15000 pregnancies [1, 2]. Although this disease is very rare, in some cases, it is associated with abnormalities of the lymph system or abnormalities of the thoracic duct [2]. Causes of pleural effusion in the neonate include immune and non-immune Turner and congenital syndrome, pulmonary, and pulmonary fluid accumulation [3]. Although low levels of pleural effusion may spontaneously be absorbed or cause no problems in the fetus and the infant, high levels of fluid can cause fetal hydrops, pulmonary hypoplasia, polyhydramnios due to pressure on the esophagus, preterm labor, and even intrauterine death [4-6]. About 9-27% of the cases are absorbed spontaneously [7], and others require treatment interventions during fetal development. Prognosis is more difficult in cases of the disease accompany with hydrops fetalis, the gestational age less than 35 weeks, and bilateral effusion [8]. The rate of postnatal mortality has been reported to be 37% [9].
In general, hydrothorax is primary or secondary. In the primary cases, the main cause is lymphatic vascular malformation and there is often a thoracic duct involvement that causes the accumulation of lymphatic fluid in the pleura (chylothorax) [10]. In secondary cases, hydrothorax is usually a component of hydrops that can have immunological or non-immunological causes. Thoracentesis is through skin, diagnostic and therapeutic method [11] that it has been shown that one time thoracentesis can remove the problem in 27% of the cases, and there is no requirement for any other therapeutic action [5]. However, in most cases, fluid is re-accumulated and the risk of formation of hydrops remains with the lupus hypoplasia. In these cases, administration of the thoracoamniotic shunt is helpful.

Patient and methods
The 29-year-old mother in the second pregnancy at the age of 31 weeks of gestation, with a diagnosis of severe pleural effusion in the right side of the embryo chest, was referred to the perinatology group of the Sarem Specialized Hospital. In the ultrasound, severe pleural effusion was seen on the right side, along with the right role collapse, which caused the heart and mediastinum to move to the opposite side (Fig. 1). Amniotic fluid level was higher than normal (AFI=220) and anomalies or abnormality were not reported in the ultrasound. In embryonic echocardiography, mild pericardial effusion with mild right ventricular hypertrophy was reported without congenital heart anomalies and normal heart rhythm. Screening tests for the fetus were normal. The result of the first pregnancy is a healthy two year old girl.

Fig. 1) Embryonic ultrasound image, severe pleural effusion with lung collapse

Regarding severe hydrothorax, right lung collapse, compressive effects on the heart and lungs were performed by the simultaneous ultrasonography of the embryo and thoracentesis through the mother`s skin and a clear liquid of about 100 cc was removed from the pleural space and was sent to the laboratory for examination (Fig. 2). Ultrasonography while doing thoracentesis revealed a drainage of the right hemi thorax and the opening of the right lung with the modification of the heart and mediastinal shift. In the study, aspirated fluid contained 95% lymphocyte indicating fluid chilotouracticity. The performed karyotype was 46xy and normal and the presence of Turner syndrome was also ruled out. After 2 days, an ultrasound scan was performed again in which accumulation of fluid in the right pleural space with mild left hydrothorax, generalized skin edema and bilateral hydrocele were observed.

Fig. 2) Pleural effusion aspiration via the mother`s skin through ultrasound, lung opening at the same time as fluid drainage

The next day, the mother was referred to Caesarean Section because of the rupture of amniotic sac and early labor pain. At birth, the baby was placed in the operation room and under tracheal tube for lack of proper respiration and heart rate under 60, and received an adrenaline injection. At the same time, the fluid in the thoracic space was aspirated with an angiocatheter and about 120cc of fluid was removed from the pleural space. After that, the baby`s heart rate and respiration were better and then the baby was transferred to the NICU.
The examination, showed the edema throughout the skin and the sclerotium. In the NICU, the baby was given a double-sided chest tube and he was attached to the ventilator, given the continued respiratory distress and fluid retention in the pleural space. In abdominal ultrasonography, medium bilateral hydronephrosis was shown and the baby had no evidence of hemolysis or anemia in the tests. Echocardiography also did not show structural abnormalities or functional defects. The mother and baby were examined for rubella, cytomegalovirus, HIV, and herpes simplex viruses, as well as toxoplasma, chlamydia, and mycoplasma injections, which were not detected.
Gradually, the edema was resolved within a week and with lower discharge of the chest tube, first the left tube and then the right tube were removed and finally the infant was discharged with a good general condition.
 
Discussion
Chylothorax or the accumulation of lymph fluid in pleural space is the most common cause of the occurrence of opioid pleural effusion during embryonic development [12]. In the patient, the other causes of hydrothorax were fully evaluated. Serology for congenital infections (TROCH) was negative in mother and infant and there was no evidence of hemolysis in the infant. Karyotype and echocardiography were normal and according to the analysis of aspirated fluid from the pleural space, the presence of chylothorax was confirmed. The cause of chylothorax is often an abnormality in the thoracic duct. Embryo hydrothorax can be rarely absorbed spontaneously [12]. In mild cases, therapeutic treatments is serial sonography from the embryo. However, in cases where hydrothorax causes pressure on the lungs and heart, lung collapse and ultimately pulmonary hypolysis may occur, and in the pressure on cardiovascular system can lead to hydrops in the fetus. Hydrops cases are followed by mortality in 50% of the cases. In the patient we considered, due to the severity of hydrothorax and lung collapse, fluid drainage was important in reducing pressure on the lungs, heart and mediastinum arteries and eventually preserving the fetus. In these cases, thoracosynthesis is initially performed with ultrasound [5], which in our patient was removed by drainage of the collapse fluid and the fluid pressure on the heart. However, after a few days, the fluid was re-accumulated and the fetus involved with hydrops due to pressure on the heart and mediastinum vessels. Hydrothorax is a common complication of thoracosynthesis that insertion of shunt between pleural space and amniotic fluid is the next stage of treatment that in this particular case, before placing the shunt, the mother experienced premature labor pain and rupture of amniotic sac.
Most studies have suggested thoracosynthesis as a primary action in the treatment of hydrothorax, and it is recommended that thoracoamniotic shunt be administrated in case of recurrence of the diseases [12]. However, cases of hydrothorax treatment with two stages of thoracosynthesis in fetus have also been reported.
 
Conclusion
Hydrothorax is a rate fetal disease that if is not treated promptly can lead to fetal hydrops or pulmonary hypoplasia and is accompanied with high mortality after birth. In such cases, early discharge of pleural fluid plays an important role in treating the disease and preventing complications. Given the high risk of recurrence of hydrothorax, serial sonography is recommended after thoracosynthesis. It seems that the age of the diagnosis of hydrothorax and its timely treatment play an important role in the prognosis of the disease.
 
Acknowledgements
The case was not found by the authors.
Ethical permissions
The case was not found by the authors.
Conflict of interests
The case was not found by the authors.
Financial support
This study was supported by Sarem Fertility and Infertility Research Center.
Contribution of authors
Abotaleb Saremi (First author), author of the article/ main author (%40); Seyed Maziyar Mortazavi (Second author), author of the article/ methodology/ main author/ author of discussion (%40); Hassan Ali Ahmadi (third author), author of the article/ helper author (%20).