Back to Search Results


Nonimmune Hydrops Fetalis

Author: Ralph K. Tamura, MD

Editor: Vanessa Gregg. MD

Registered users can also download a PDF or listen to a podcast of this Pearl.
Log in now, or create a free account to access bonus Pearls features.

Hydrops fetalis is the presence of excessive fluid in two or more fetal compartments including skin edema, pleural effusion, pericardial effusion, ascites, and polyhydramnios. Fetal hydrops can be immune or nonimmune. Ninety percent are nonimmune (not the result of red cell alloimmunization).

Nonimmune hydrops fetalis (NHF) can present as uterine size greater than dates due to polyhydramnios, decreased fetal movement, fetal compromise on fetal testing, and ultrasound findings. The diagnosis is made when increased amounts of fluid are seen in at least two fetal compartments. Ascites is an early sign and must be differentiated from pseudoascites. Pleural effusions may be unilateral or bilateral. Skin edema is usually a late sign and subcutaneous or scalp edema of greater than 5 mm is pathologic. Polyhydramnios is present in the majority of cases. The placenta may be abnormal in appearance (intervillous edema) and in thickness (thicker in certain infections or thin or compressed with polyhydramnios).

When the results both antenatal and postnatal evaluation are included, etiology of NHF can be determined in 60-85% of cases. Some common etiologies are:

  1. Aneuploidy has been reported in about 13% of cases. Monosomy X is the most common chromosomal cause. Trisomies 21, 18, 13, other very rare trisomies, and tetraploidy/triploidy are associated with most of the remainder. The prognosis is poor and NHF likely results from fluid accumulation due to cystic hygromas, obstruction or abnormalities in the lymphatic system, or cardiac defects. Certain genetic syndromes may also be associated, including skeletal dysplasias.
  2. Fetal metabolic storage diseases cause hydrops due to congestion caused by accumulation of metabolites in the liver and other abdominal viscera. Recurrence in subsequent pregnancies may be as high as 25%.
  3. Cardiovascular anomalies account for 20% of cases. Common intracardiac structural defects include hypoplastic left heart and isolated ventricular and atrial septal defects. Tachy- and bradyarrhythmias may cause high or low output cardiac failure. Vascular abnormalities including chorioangiomas of the placenta, fetal tumors, hemangiomas, umbilical cord aneurysms, and obstruction of the vena cava, portal vein, or femoral vessels can cause high output failure.
  4. Thoracic abnormalities such as congenital adenomatoid malformations of the lung increase intrathoracic pressure and obstruct venous return to the heart, resulting in peripheral venous congestion. Lymphatic obstruction may cause lymphedema.
  5. Anemia from hemorrhage, hemolysis, defective red cell production or abnormal hemoglobin production accounts for up to 25%. The pathogenesis involves high output cardiac failure. Hydrops may resolve in some cases when the anemia is corrected.
  6. Congenital Infections with toxoplasmosis, rubella, cytomegalovirus, and herpes (TORCH) organisms, parvovirus B19, syphilis, varicella, adenovirus, and coxsackie virus cause up to 8% of NHF. The mechanism is not clearly understood with all infections. Parvovirus causes hemolysis, hepatitis, and myocarditis.
  7. Gastrointestinal tract anomalies such as midgut volvulus result in ascites, edema, and polyhydramnios.
  8. Twin-to-twin transfusion syndrome in monochoroionic twins may result in NHF.


Evaluation includes:

  • Patient history regarding ethnicity, genetic abnormalities, metabolic diseases, and recent exposure to infections
  • Ultrasound examination for structural defects
  • Doppler assessment for middle cerebral artery peak systolic velocity for detection of anemia
  • Laboratory tests include:
  • Complete blood count with RBC indices
  • Blood type and screen
  • Serologic evaluation for infection
  • Kleihauer-Betke acid elution
  • Fetal karyotype
  • Amniotic fluid assessment
  • Umbilical blood sampling as indicated


Management depends on the cause. Mortality can be high and is generally higher with earlier gestational age at onset and with etiologies not amenable to intrauterine intervention. Management may include pregnancy termination, therapeutic interventions when appropriate, and supportive care as needed. Antenatal surveillance includes nonstress testing, biophysical profile, and Doppler studies as needed. Delivery should occur at a tertiary center with coordination by subspecialty personnel.


Further Reading:

Society for Maternal-Fetal Medicine (SMFM), Norton ME, Chauhan SP, Dashe JS. Society for maternal-fetal medicine (SMFM) clinical guideline #7: nonimmune hydrops fetalis. Am J Obstet Gynecol. 2015 Feb;212(2):127-39. doi: 10.1016/j.ajog.2014.12.018. Epub 2014 Dec 31.


Initial approval January 2009; Revised January 2018. Reaffirmed July 2019


********** Notice Regarding Use ************

The Foundation for Exxcellence in Women’s Health, Inc (“Foundation”) is committed to accuracy and will review and validate all Pearls on an ongoing basis to reflect current practice.

This document is designed to aid practitioners in providing appropriate obstetric and gynecologic care. Recommendations are derived from major society guidelines and high quality evidence when available, supplemented by the opinion of the author and editorial board when necessary. It should not be construed as dictating an exclusive course of treatment or procedure to be followed.

Variations in practice may be warranted when, in the reasonable judgment of the treating clinician, such course of action is indicated by the condition of the patient, limitations of available resources, or advances in knowledge or technology. The Foundation reviews the articles regularly; however, its publications may not reflect the most recent evidence. While we make every effort to present accurate and reliable information, this publication is provided “as is” without any warranty of accuracy, reliability, or otherwise, either express or implied. The Foundation does not guarantee, warrant, or endorse the products or services of any firm, organization, or person. Neither the Foundation, the ABOG, SASGOG nor their respective officers, directors, members, employees, or agents will be liable for any loss, damage, or claim with respect to any liabilities, including direct, special, indirect, or consequential damages, incurred in connection with this publication or reliance on the information presented.

Copyright © 2019 - The Foundation for Exxcellence in Women's Health, Inc. All rights reserved. No publication, reuse or dissemination allowed without written permission.


Back to Search Results