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PubMed This is a summary of 25 peer-reviewed journal articles Updated
Pediatrics · Sickle Cell Disease

What Does a Positive Sickle Cell Newborn Screen Mean?

At a Glance

A newborn screening test checks your baby's blood for abnormal hemoglobin shortly after birth. If positive for sickle cell disease, a confirmatory DNA test identifies the exact subtype. Early diagnosis allows doctors to start life-saving preventative treatments, like daily penicillin, by two months of age.

In this answer

4 sections

01

The Initial Screen: What to Expect

02

How the Screening Tests Work

03

Confirming the Exact Type

04

Why Early Diagnosis is Crucial

Receiving a positive newborn screen can be frightening for new parents, but you are not alone, and early treatments are highly effective. In the United States, you will typically know if your baby has a form of sickle cell disease (SCD) within the first one to two weeks after birth [1][2]. Every state requires a universal newborn screening test, which checks for sickle cell disease and other conditions using a few drops of blood collected from your baby’s heel shortly after they are born [1][3]. If the initial screen shows signs of sickle cell disease, your doctor will order follow-up testing, often involving genetic tests, to confirm the exact type (such as HbSS, HbSC, or HbS beta thalassemia) within the first month of life [4][5].

The Initial Screen: What to Expect

Universal newborn screening for sickle cell disease is a standard public health practice across the US [1][6].

  • The Heel Prick: Before your baby leaves the hospital—usually at 24 to 48 hours of age—a nurse will prick their heel to collect a small blood sample on a special paper card [3].
  • State Laboratories: The sample is sent to a state public health lab for analysis. Because programs are run by individual states, the exact testing methods and reporting times can vary slightly [2][7].
  • The Results: If the screen is positive for a hemoglobin disorder, the lab immediately notifies your baby’s pediatrician, who will then contact you to discuss the next steps [8]. Tip: Make sure the hospital has your correct, up-to-date phone number and address before discharge so there are no delays in reaching you.

How the Screening Tests Work

The initial newborn screen looks at the types of hemoglobin (the oxygen-carrying protein in red blood cells) present in your baby’s blood. Most state labs use specialized tests to separate and identify the different hemoglobin proteins [9].

These tests check if your baby has standard adult hemoglobin (HbA) or abnormal hemoglobins, such as sickle hemoglobin (HbS) or hemoglobin C (HbC) [9][10]. The lab will report a pattern of letters based on what they find. Some common patterns include:

  • FA: Normal (Fetal and Adult hemoglobin).
  • FAS: Indicates Sickle Cell Trait. Your baby is a healthy carrier, does not have sickle cell disease, and will live a normal life.
  • FS: Indicates the baby has fetal hemoglobin and sickle hemoglobin, but no normal adult hemoglobin. This pattern suggests sickle cell anemia (HbSS) or sickle beta-zero thalassemia (HbS beta-0 thalassemia) [4][11].
  • FSC: Indicates fetal, sickle, and C hemoglobin, pointing to HbSC disease.

Note: If your baby was born prematurely or received a blood transfusion shortly after birth, it can alter the screening results, which is why your doctor must know your baby’s full medical history [12].

Confirming the Exact Type

While the initial protein tests are excellent for flagging a problem, they cannot always provide the definitive exact diagnosis [4][11]. For example, the “FS” pattern looks identical for both HbSS and HbS beta-0 thalassemia on the initial screening [4][11].

Because knowing the exact subtype guides your baby’s lifelong medical care, a positive newborn screen must be followed by confirmatory testing [4][13]. Today, this often involves molecular genetic (DNA) testing [4][14]. DNA testing looks directly at your baby’s genes to identify the specific genetic mutations they inherited, offering a definitive and highly precise diagnosis of their exact sickle cell genotype [14][15][16].

Why Early Diagnosis is Crucial

The main goal of newborn screening is not just to provide a diagnosis, but to get your baby into a comprehensive care program before they ever experience symptoms [17][18]. Finding out the exact sickle cell type early allows doctors to start preventative care immediately, which helps children with SCD live much longer, healthier lives [19][20][21].

Once a diagnosis is confirmed, your care team will likely initiate the following measures by the time your baby is two to three months old:

  • Prophylactic Penicillin: Daily doses of this antibiotic are given to prevent severe bacterial infections (like pneumococcal disease). This is typically taken daily until at least age 5 [19][22].
  • Specialized Immunizations: Babies with SCD receive an augmented vaccination schedule for extra protection against infections [23].
  • Referral to a Specialist: You will be connected with a pediatric hematologist (a doctor specializing in children’s blood disorders) who will monitor your child’s health and discuss future treatments, such as hydroxyurea therapy (a daily medication that helps prevent red blood cells from sickling) [24][25].

IMPORTANT SAFETY WARNING: For an infant with sickle cell disease, a fever is a life-threatening medical emergency. If your baby has a temperature of 100.4°F (38°C) or higher, you must seek immediate emergency medical care.

Common questions in this guide

What does the FS pattern mean on my baby's newborn screen?
The FS pattern indicates your baby has fetal hemoglobin and sickle hemoglobin, but no normal adult hemoglobin. This suggests they may have sickle cell anemia (HbSS) or sickle beta-zero thalassemia, which requires confirmatory DNA testing to diagnose exactly.
How long does it take to get newborn sickle cell screening results?
You will typically find out if your baby has a form of sickle cell disease within the first one to two weeks after birth. If the initial screen is positive, your doctor will order follow-up testing to confirm the exact type within the first month of life.
Why does my baby need another test after a positive newborn screen?
The initial blood test flags abnormal hemoglobin proteins but cannot always pinpoint the exact type of sickle cell disease. A confirmatory molecular DNA test looks directly at your baby's genes to identify their specific subtype, which is essential for guiding their lifelong medical care.
When do babies with sickle cell disease start preventative treatment?
Once the exact diagnosis is confirmed, your care team will usually start preventative measures by the time your baby is two to three months old. This standard care includes daily prophylactic penicillin to prevent severe bacterial infections.
What should I do if my baby with sickle cell disease gets a fever?
A fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher in an infant with sickle cell disease is a life-threatening medical emergency. You must seek immediate emergency medical care without delay.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What specific hemoglobin letter pattern (like FS or FSC) did my baby's newborn screen show, and what exactly does it mean?
  2. 2.When and how will we do the confirmatory DNA testing to find out my baby's exact sickle cell subtype?
  3. 3.Can you refer us to a comprehensive pediatric sickle cell clinic or hematologist?
  4. 4.When do we start the daily prophylactic penicillin, and what is the exact dosage for my baby's weight?
  5. 5.Could I please get a physical copy of the newborn screening lab report for my records?

Questions For You

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References

References (25)
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    Newborn Screening for Hemoglobinopathies and Thalassemias: Brief History, Recent Activities, and Global Status-2026.

    Therrell BL

    International journal of neonatal screening 2026; (12(1)) doi:10.3390/ijns12010008.

    PMID: 41718422
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    Newborn Screening for Sickle Cell Disease and Thalassemia.

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    JAMA health forum 2025; (6(3)):e250064 doi:10.1001/jamahealthforum.2025.0064.

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    Unveiling the Burden of Sickle Cell Anemia: A Pilot Study Validating Dried Blood Spots for Newborn Screening.

    Karra ML, Rahiman EA, Narahari M, et al.

    Indian journal of pediatrics 2025; (92(4)):405-408 doi:10.1007/s12098-024-05392-8.

    PMID: 39754675
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    Clinical Utility of the Addition of Molecular Genetic Testing to Newborn Screening for Sickle Cell Anemia.

    Shook LM, Haygood D, Quinn CT

    Frontiers in medicine 2021; (8()):734305 doi:10.3389/fmed.2021.734305.

    PMID: 34859003
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    Hemoglobin Chapel Hill masquerading as hemoglobin S in newborn sickle cell screening: A case study.

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    Newborn Screening for SCD in the USA and Canada.

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    Newborn Screening for Sickle Cell Disease in the United States: Gaps in Medical Care for the Pediatric Clinicians.

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    Process evaluation of co-designed interventions to improve communication of positive newborn bloodspot screening results.

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    Newborn Screening for Sickle Cell Disease and Other Hemoglobinopathies: A Short Review on Classical Laboratory Methods-Isoelectric Focusing, HPLC, and Capillary Electrophoresis.

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    Newborn Screening With Sickle Cell Point of Care: A Valuable Resource in Low-Income Settings.

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    Difficulties in the diagnosis of HbS/beta thalassemia: Really a mild disease?

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    New approach to accurate interpretation of sickle cell disease newborn screening by applying multiple of median cutoffs and ratios.

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    Pediatric blood & cancer 2018; (65(9)):e27230 doi:10.1002/pbc.27230.

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    Clinical Utility of Confirmatory Genetic Testing to Differentiate Sickle Cell Trait from Sickle-β+-Thalassemia by Newborn Screening.

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    [Difficulties caused by hemoglobin variants in the assessment of hemoglobin A1c regarding two cases].

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This page provides educational information about newborn screening for sickle cell disease. Always consult your pediatrician or a pediatric hematologist regarding your baby's specific test results, diagnosis, and medical care.

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