Skip to content
Inciteful Med

Diagnostic Testing: Uncovering the 'Why' Behind NIHF

Last updated:

The diagnostic workup for non-immune hydrops fetalis (NIHF) aims to identify the underlying cause of fetal fluid buildup. This process typically includes a detailed ultrasound, a fetal echocardiogram to check heart function, maternal blood tests for infections, and tiered genetic testing.

Key Takeaways

  • • A detailed ultrasound and fetal echocardiogram are critical first steps to confirm fluid buildup and assess the baby's heart function.
  • • Maternal blood tests, including the indirect Coombs test, are used to confirm the hydrops is non-immune and rule out infections like Parvovirus B19.
  • • Genetic testing is standard for NIHF and usually begins with a karyotype and chromosomal microarray (CMA) via amniocentesis.
  • • If initial genetic tests are normal, Whole Exome Sequencing (WES) is recommended and can identify the underlying cause in roughly a third of unexplained cases.
  • • Maternal health must be closely monitored throughout the diagnostic process for signs of maternal mirror syndrome, such as high blood pressure and rapid swelling.

When a baby is diagnosed with non-immune hydrops fetalis (NIHF), the medical team must act quickly to solve a complex puzzle. This process, called a diagnostic workup, is designed to uncover the “why” behind the fluid buildup [1]. Identifying the exact cause is the most important step in determining the prognosis and exploring potential treatment options [2].

The Initial Evaluation: Ruling Out the ‘Knowns’

The first steps focus on confirming the diagnosis and ruling out the most common or treatable causes.

1. Detailed Ultrasound and Fetal Echocardiogram

A specialized ultrasound confirms fluid in at least two body compartments (like the belly or lungs) and looks for other physical anomalies [3]. A fetal echocardiogram is a highly detailed ultrasound of the baby’s heart, performed by a pediatric cardiologist or a specialist in maternal-fetal medicine [4].

  • Cardiovascular Profile Score (CVPS): During this exam, doctors may use a scoring system called the CVPS to assess heart health [5]. It looks at five markers, including heart size, valve function, and blood flow [6]. A score of 10 is normal; a lower score (especially 7 or below) suggests the heart is struggling to pump effectively [7][8].

2. Maternal Blood Tests

Several blood tests are performed on the mother to rule out “immune” causes and common infections:

  • Indirect Coombs Test: This confirms the hydrops is “non-immune” by checking for maternal antibodies that could attack the baby’s red blood cells [9][4].
  • Infection Screening (TORCH and Parvovirus): Doctors test for infections like Parvovirus B19 (Fifth Disease) and CMV (Cytomegalovirus) [9][10]. Because some maternal tests can be inconclusive, doctors may also use a more sensitive test called PCR to look for the virus’s DNA [9][11].

Genetic Testing: The Deep Dive

Since many cases of NIHF are caused by genetic changes, a “tiered” approach to testing is standard. These tests usually require an amniocentesis (collecting a small sample of amniotic fluid) [12].

Tier 1: Karyotype and Chromosomal Microarray (CMA)

These are the standard first-line genetic tests:

  • Karyotype: Looks for large-scale changes, such as an extra or missing chromosome (e.g., Down syndrome) [12].
  • Chromosomal Microarray (CMA): A much more detailed look that can find tiny “micro-deletions” or “micro-duplications” of genetic material that a standard karyotype would miss [12][13].

Tier 2: Whole Exome Sequencing (WES)

If the Karyotype and CMA are normal, Whole Exome Sequencing (WES) is now strongly recommended [12][13]. While CMA looks at the “chapters” of the genetic book, WES reads the individual “words” to find single-gene changes [14].

  • Diagnostic Yield: In cases where standard tests are negative, WES can find the cause in approximately 29% to 37% of babies [15][16].
  • Critical Value: WES is particularly good at identifying conditions like RASopathies (e.g., Noonan syndrome) or metabolic disorders that may have specific treatments [16][17].

Fetal Diagnostic Completeness Checklist

To ensure no stone is left unturned, your care team should ideally complete the following for the baby:

  • [ ] Detailed Ultrasound (to confirm 2+ fluid compartments) [3]
  • [ ] Fetal Echocardiogram (including a CVPS score) [4][5]
  • [ ] Maternal Antibody Screen (Indirect Coombs) [9]
  • [ ] Infection Panel (Parvovirus B19, CMV, etc.) [10]
  • [ ] Amniocentesis for Karyotype or CMA [12]
  • [ ] Whole Exome Sequencing (if CMA is normal) [13][15]

Maternal Safety Checklist

Simultaneously, the medical team must constantly evaluate the mother’s safety.

  • [ ] Maternal Mirror Syndrome Screening (closely checking the mother’s blood pressure, breathing, and looking for rapid weight gain/swelling) [18]

Return to Introduction

Frequently Asked Questions

Why is an indirect Coombs test done for hydrops fetalis?
An indirect Coombs test is performed on the mother's blood to check for antibodies that could be attacking the baby's red blood cells. A negative result confirms that the fluid buildup is 'non-immune' rather than caused by an immune system response.
What is a Cardiovascular Profile Score (CVPS) in a fetal echocardiogram?
The CVPS is a 10-point scoring system used during a fetal echocardiogram to evaluate the baby's heart health. It looks at factors like heart size and valve function to determine if the heart is pumping effectively, which is crucial for managing NIHF.
What genetic tests are used to find the cause of NIHF?
Doctors usually begin with a karyotype and chromosomal microarray (CMA) using fluid from an amniocentesis. If those initial tests do not find an answer, Whole Exome Sequencing (WES) is strongly recommended to search for single-gene changes.
How do doctors check for maternal mirror syndrome during an NIHF pregnancy?
The medical team monitors the mother for sudden, severe swelling, high blood pressure, and rapid weight gain. These symptoms can indicate maternal mirror syndrome, a serious complication that requires immediate medical attention to protect the mother's health.

Questions for Your Doctor

  • • How many fetal compartments currently show fluid, and has this changed since the last ultrasound?
  • • Was the maternal antibody screen (indirect Coombs) negative, confirming this is 'non-immune'?
  • • What was the baby's Cardiovascular Profile Score (CVPS), and which specific heart functions (like valve leakage or heart size) affected the score?
  • • If the initial chromosomal microarray (CMA) is normal, what is the plan and timeline for starting Whole Exome Sequencing (WES)?
  • • Have we ruled out infections like Parvovirus B19 using both maternal blood work and PCR testing?

Questions for You

  • • Has the doctor mentioned any other structural findings, like a small chin or a heart defect, besides the fluid?
  • • Am I experiencing any new symptoms like sudden, severe swelling, high blood pressure, or unusual weight gain?
  • • Do we have a family history of blood disorders (like thalassemia) or genetic conditions that we should share?
  • • How are we feeling about the timeline for testing? Do we need more information to decide on an amniocentesis for genetic testing?

Want personalized information?

Type your question below to get evidence-based answers tailored to your situation.

References

  1. 1

    No. 363-Investigation and Management of Non-immune Fetal Hydrops.

    Désilets V, De Bie I, Audibert F

    Journal of obstetrics and gynaecology Canada : JOGC = Journal d'obstetrique et gynecologie du Canada : JOGC 2018; (40(8)):1077-1090 doi:10.1016/j.jogc.2017.12.011.

    PMID: 30103882
  2. 2

    Nonimmune hydrops fetalis: Genetic analysis and clinical outcome.

    Deng Q, Fu F, Yu Q, et al.

    Prenatal diagnosis 2020; (40(7)):803-812 doi:10.1002/pd.5691.

    PMID: 32267001
  3. 3

    Outcome and etiology of fetal pleural effusion, fetal ascites and hydrops fetalis after fetal intervention: retrospective observational cohort from a single institution.

    Wu WJ, Ma GC, Chang TY, et al.

    Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology 2024; (63(4)):536-543 doi:10.1002/uog.27501.

    PMID: 37767652
  4. 4

    A Rare Association of Non-Compaction of the Ventricular Myocardium, and Non-Immune Hydrops Fetalis.

    Nandyal R, Moorthy G

    The Journal of the Oklahoma State Medical Association 2016; (109(4-5)):146-50.

    PMID: 27328555
  5. 5

    The Cardiovascular Profile Score in Patients with Non-immune Hydrops Fetalis and Cardiac Anomalies - a Pilot Study.

    Dionysopoulou A, Pirih E, Macchiella D, et al.

    Reproductive sciences (Thousand Oaks, Calif.) 2023; (30(9)):2805-2812 doi:10.1007/s43032-023-01216-w.

    PMID: 36988903
  6. 6

    Fetal Cardiovascular Profile Score (CVPs) in Fetal Anemia, Using Fetal Hemoglobin Bart's Disease at Mid-Pregnancy as a Study Model.

    Hantrakun P, Srisupundit K, Tongsong T

    Diagnostics (Basel, Switzerland) 2025; (15(18)) doi:10.3390/diagnostics15182303.

    PMID: 41008675
  7. 7

    Fetal Surveillance in High-Risk Fetal Cardiac Disease: Frequency, Results and Relationship with Survival.

    Samuel R, Trakulmungkichkarn T, Hornberger LK, et al.

    Journal of obstetrics and gynaecology Canada : JOGC = Journal d'obstetrique et gynecologie du Canada : JOGC 2024; (46(12)):102690 doi:10.1016/j.jogc.2024.102690.

    PMID: 39413873
  8. 8

    Fetal Echocardiographic Variables Associated with Pre-Surgical Mortality in Truncus Arteriosus: A Pilot Study.

    Cox K, Husain N, Jhaveri S, et al.

    Pediatric cardiology 2023; (44(6)):1397-1405 doi:10.1007/s00246-023-03099-9.

    PMID: 36854855
  9. 9

    Human parvovirus B19 vertical infection and hydrops fetalis. A case report.

    Boggio GA, Moreno L, Di Cuatro N, et al.

    Archivos argentinos de pediatria 2025; (123(3)):e202410420 doi:10.5546/aap.2024-10420.eng.

    PMID: 39401166
  10. 10

    Progressive non-immune hydrops fetalis associated with RASA1 mutation: prenatal imaging and genomic insights.

    Borthakur K, Mali N, Borthakur I

    BMJ case reports 2026; (19(2)) doi:10.1136/bcr-2025-270831.

    PMID: 41763666
  11. 11

    Dual pathology of parvovirus B19 infection and Aicardi-Goutières syndrome complicating non-immune hydrops fetalis.

    Shekhawat DS, Das S, Sharma C, et al.

    BMJ case reports 2025; (18(7)) doi:10.1136/bcr-2025-266781.

    PMID: 40744631
  12. 12

    Fetal Hydrops: Genetic Dissection of an Unspecific Sonographic Finding-A Comprehensive Review.

    Mastromoro G, Guadagnolo D, De Luca A, et al.

    Diagnostics (Basel, Switzerland) 2025; (15(4)) doi:10.3390/diagnostics15040465.

    PMID: 40002616
  13. 13

    An Investigation of the Etiologies of Non-Immune Hydrops Fetalis in the Era of Next-Generation Sequence-A Single Center Experience.

    Wei X, Yang Y, Zhou J, et al.

    Genes 2022; (13(12)) doi:10.3390/genes13122231.

    PMID: 36553497
  14. 14

    Exome sequencing vs targeted gene panels for the evaluation of nonimmune hydrops fetalis.

    Norton ME, Ziffle JV, Lianoglou BR, et al.

    American journal of obstetrics and gynecology 2022; (226(1)):128.e1-128.e11 doi:10.1016/j.ajog.2021.07.014.

    PMID: 34331894
  15. 15

    Fetal hydrops and the Incremental yield of Next-generation sequencing over standard prenatal Diagnostic testing (FIND) study: prospective cohort study and meta-analysis.

    Mone F, Eberhardt RY, Hurles ME, et al.

    Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology 2021; (58(4)):509-518 doi:10.1002/uog.23652.

    PMID: 33847422
  16. 16

    Diagnostic yield from prenatal exome sequencing for non-immune hydrops fetalis: A systematic review and meta-analysis.

    Al-Kouatly HB, Shivashankar K, Mossayebi MH, et al.

    Clinical genetics 2023; (103(5)):503-512 doi:10.1111/cge.14309.

    PMID: 36757664
  17. 17

    Genetic etiologies associated with non-immune hydrops fetalis delineated by whole exome sequencing: A pilot series and its implications in prenatal genetic counseling.

    Lim ZW, Ma GC, Chang TY, et al.

    The journal of obstetrics and gynaecology research 2025; (51(8)):e70039 doi:10.1111/jog.70039.

    PMID: 40789765
  18. 18

    Mirror syndrome and placental ectopic liver in association with de novo SOS1 variant.

    Tanaka Y, Ikenoue S, Ueno A, et al.

    European journal of medical genetics 2025; (77()):105039 doi:10.1016/j.ejmg.2025.105039.

    PMID: 40829732

This page explains diagnostic testing for non-immune hydrops fetalis for educational purposes. Always consult your maternal-fetal medicine specialist or genetic counselor for interpretation of your specific ultrasound and genetic test results.

Stay up to date

Get notified when new research about Non-immune hydrops fetalis is published.

No spam. Unsubscribe anytime.