ABSTRACT
Isolated fetal pleural effusion is typically caused by agenesis or atresia of the lymphatic duct and can lead to lung compression, pulmonary hypoplasia, polyhydramnios, mediastinal shift, cardiac dysfunction, and fetal hydrops. Medium‐chain triglycerides (MCTs), compared to long‐chain fatty acids (LCFAs), are absorbed directly into the portal venous system, bypassing the lymphatic system during digestion, which reduces chyle production. We present two cases of severe unilateral fetal pleural effusion that completely resolved after maternal intake of MCTs and a restricted LCFA diet.
Keywords: case report, fetal echocardiography, fetal pleural effusion, MCT oil
Summary.
Fetal pleural effusions resulting from impairment of the lymphatic duct and chyle accumulation cause pulmonary hypoplasia, cardiac dysfunction, and fetal hydrops.
Medium‐chain triglycerides (MCTs) are absorbed directly into the portal system, bypassing the lymphatic system and reducing chyle production.
Maternal intake of MCTs would regress severe primary fetal pleural effusion.
1. Introduction
Fetal pleural effusion is a rare abnormality resulting from fluid accumulation in the chest cavity [1]. The incidence of isolated pleural effusions in pregnancy is 1 in 10,000 to 15,000 live births [2].
The underlying causes may include genetic disorders, infections, and heart or lung malformations. Prognosis depends on etiology, gestational age at presentation, associated malformations, and disease severity. In isolated primary cases, the fluid is typically chyle, resulting from agenesis, fistula, or atresia of the lymphatic duct [3].
Severe pleural effusion can cause lung compression and may lead to pulmonary hypoplasia. It can also interfere with normal fetal swallowing, resulting in polyhydramnios. Mediastinal shift and cardiac dysfunction typically occur in severe unilateral cases, potentially leading to fetal hydrops [1, 3]. Primary fetal pleural effusions may remain stable, resolve spontaneously, or progress to severe forms and fetal hydrops during pregnancy [3]. In isolated, non‐progressive cases, pregnancy outcomes are generally favorable [4]. More than 50% of isolated primary cases remain stable or resolve without requiring intrauterine interventions. Fetal interventions, such as thoracocentesis and thoracoamniotic shunt insertion, become necessary in severe or progressive forms with cardiac impairment or fetal hydrops [3, 4]. In bilateral severe forms of pleural effusion, repeated thoracocentesis may be a diagnostic and therapeutic option to decompress the fetal lung and ensure sufficient pulmonary development and improve perinatal outcome [5]. However, thoracoamniotic shunting is an invasive method and not available in all centers.
MCTs, compared to LCFAs, are absorbed directly into the portal venous system, bypassing the lymphatic system during digestion and reducing chyle production [6]. The success of feeding with defatted milk in treating neonatal congenital chylothorax has been demonstrated in various studies [7, 8, 9, 10]. Nutrients such as LCFAs flow through the placenta from the mother to the fetus [10, 11]. Therefore, we hypothesize that maternal intake of MCTs and a restricted LCFA diet would effectively regress severe forms of primary fetal pleural effusion. We present the outcomes of two cases with severe progressive isolated fetal pleural effusion who underwent a maternal MCTs diet. In all cases, detailed fetal anatomical scans revealed no other structural abnormalities. Fetal middle cerebral artery peak systolic velocity (MCA‐PSV), fetal echocardiography, genetic testing, and TORCH panel results were normal.
2. Case 1
2.1. Case History/Examination
A 34‐year‐old woman, gravida 1, with a consanguineous pregnancy, was referred to our center at 18 weeks of gestational age (GA) with massive left‐sided pleural effusion, significant heart shifting, and minimal subdiaphragmatic ascites (Figure 1). The result of amniocentesis indicated “46.XY,inv(q31.3q.32.)mat” which is a normal variant and was also present in the mother's karyotype. Fetal anatomical scans and echocardiography revealed no other structural abnormalities. Counseling with the parents regarding the option of a fetal thoracoamniotic shunt was conducted, but they refused any intervention;
FIGURE 1.
Pleural effusion, significant heart shifting, and minimal subdiaphragmatic ascites before MCT Oil‐based diet.
2.2. Investigations and Treatment
The option of a maternal MCTs dietary regime was discussed. After obtaining informed consent, the mother underwent a restricted LCFA diet and was advised to use MCT oils instead. Ultrasound examinations were performed weekly, evaluating amniotic fluid index (AFI), MCA Doppler, fetal growth, and the amount of fluid accumulation in the chest cavity subjectively.
2.3. Conclusion and Results
There were no significant changes in the amount of pleural effusion until 3 weeks, but after that, the amount of effusion subjectively decreased. By the sixth week of follow‐up, the ascites had completely resolved, and the pleural effusion had significantly decreased. The pleural effusion was completely absorbed by 32 weeks of gestation (Figure 2). The boy was born at 38 weeks GA with an APGAR score of 9 at 5 min, without any respiratory problems after birth. The baby was monitored for 6 months following birth and demonstrated no complications during this period.
FIGURE 2.
Regression of pleural effusion after MCT Oil‐based diet.
3. Case 2
3.1. Case History/Examination
A 31‐year‐old woman, G1, desired pregnancy after 6 years of infertility. She was referred due to left‐sided moderate to severe pleural effusion (Figure 3A) with a flattened diaphragm, heart shifting, and an AFI of 29 mm (polyhydramnios). After confirming the primary type, counseling with the parents regarding thoracocentesis and thoracoamniotic shunt was performed. Soon after drainage, both lungs expanded nicely, and the heart shift corrected completely. The mother underwent weekly follow‐up sonography. Unfortunately, a severe amount of fluid accumulation occurred on the fifth day.
FIGURE 3.
(A) Pleural effusion, flattened diaphragm, heart shifting before MCT Oil‐based diet. (B) Regression of pleural effusion after MCT oil‐based diet.
3.2. Investigations and Treatment
Parents discussed the MCTs regimen at 22 weeks GA, and she was followed up with weekly sonography scans.
3.3. Conclusion and Results
After 5 weeks, the amount of pleural effusion decreased. In the ultrasound examination at 30 weeks, the fluid was completely absorbed (Figure 3B); however, polyhydramnios remained until delivery. The boy was delivered with a good APGAR score without any complications after birth and is doing well at 2 months old.
4. Discussion
In this study, two fetuses with severe pleural effusion responded to maternal MCT oil diet treatment. Both presented with unilateral pleural effusion in severe form. Previously, a restricted fat diet and MCT oil were used for the treatment of chronic chylothorax in a patient with congenital lymphangiectasia [7, 8, 9]. In some studies, defatted breast milk was successfully used for the treatment of neonates with congenital chylothorax [7]. MCTs are absorbed directly into the portal venous system, bypassing the lymphatic system during digestion and reducing chyle production. Nutrients such as LCFAs flow through the placenta from the mother to the fetus [6, 11]. Therefore, we hypothesize that maternal intake of MCTs and a restricted LCFA diet would be helpful in regressing severe forms of isolated primary fetal pleural effusion. Although it is too early to conclude that a maternal MCT diet is a non‐invasive method for treating isolated primary fetal pleural effusion, the results of this study may be promising for future research.
Author Contributions
Shohreh Roozmeh: conceptualization, data curation, investigation, methodology, supervision, visualization, writing – original draft, writing – review and editing. Ali Mohammad Shakiba: data curation, methodology. Homeira Vafaei: conceptualization, data curation, project administration, visualization, writing – review and editing. Nasrin Asadi: data curation, writing – review and editing. Khadije Bazrafshan: data curation. Fatemeh Honar: data curation. Mozhde Ghiasi: data curation.
Ethics Statement
Informed written consent, data on epidemiology, and medical history were collected prospectively at the time of inclusion. Our study received ethics committee approval according to the ethical standards of Shiraz Medical University (No. IR.SUMS.REC.1402.206).
Consent
Written informed consent was obtained and signed from the patientregarding the use of the patient's information for the purpose of writing and publishing a case report.
Conflicts of Interest
The authors declare no conflicts of interest.
Acknowledgments
The authors would like to thank the two patients for permission to share their medical history for educational purposes and publication.
Roozmeh S., Shakiba A. M., Vafaei H., et al., “Maternal MCT Oil‐Based Diet in the Treatment of Primary Fetal Pleural Effusion: Case Reports,” Clinical Case Reports 13, no. 11 (2025): e70918, 10.1002/ccr3.70918.
Funding: The authors received no specific funding for this work.
Data Availability Statement
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.