Fetal hydrops – a review and a clinical approach to identifying the cause

ABSTRACT

Introduction: Fetal hydrops describes abnormal fluid accumulation in two or more extravascular fetal compartments. It is a poor prognostic sign in a fetus, and many will not survive to term. Fetal hydrops is a clinical sign rather than a diagnosis and has a multitude of different causes.

Areas covered: This review focusses on nonimmune fetal hydrops. We discuss in detail the most common etiologies such as infection and chromosomal abnormalities and cover rarer presentations of congenital malformation and single-gene disorders. We present a decision tree for the investigation of affected pregnancies.

Expert opinion: The current approach to the investigation of fetal hydrops largely revolves around identifying the abnormal pathophysiology via ultrasound imaging. We believe that as genomic testing of a pregnancy can be undertaken with increasing accuracy, speed, accessibility and at reduced cost, genetic testing will feature earlier in the future diagnostic pathway.

KEYWORDS:

• Fetal
• prenatal
• nonimmune fetal hydrops
• genomic
• exome
• lymphatic
• rasopathy
• ultrasound
• hydrops
• noninvasive prenatal diagnosis

Article highlights

• Fetal hydrops is the abnormal accumulation of fluid in two or more extravascular fetal compartments.

• Fetal hydrops confers a high risk of morbidity and mortality.

• Fetal hydrops can be divided into immune (largely materno-fetal alloimmunisation) and nonimmune.

• Nonimmune fetal hydrops can be caused by a multitude of different causes including infection, congenital malformation, chromosome abnormalities and single-gene disorders.

• The identification of fetal anemia from the second trimester is crucial to guiding further investigations.

• Many cases of fetal hydrops remain undiagnosed and we believe a significant proportion of these have underlying genetic lymphatic dysplasias.

• As exome or whole genome sequencing becomes increasingly available, genetic testing will feature earlier in the diagnostic pathway.

Acknowledgments

Prof. John Simpson acknowledges support by the Department of Health through the National Institute for Health Research comprehensive Biomedical Research Centre award to Guy’s and St Thomas’ National Health Service Foundation Trust in partnership with King’s College London and King’s College Hospital National Health Service Foundation Trust.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

E Dempsey is supported by the British Heart Foundation (FS/18/78/33932).