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PubMed This is a summary of 20 peer-reviewed journal articles Updated
Maternal-Fetal Medicine · Spina Bifida

Diagnosis: Prenatal Findings and Newborn Screenings

At a Glance

Spina bifida is typically diagnosed during pregnancy using MSAFP blood tests, high-resolution ultrasounds, and fetal MRIs. For newborns, doctors look for skin markers like deep sacral dimples or hair tufts, which may prompt further imaging like spinal ultrasounds or MRIs.

Diagnosis often begins during pregnancy with routine screenings, but for some families, the journey starts in the delivery room. Whether your child’s condition was identified through a blood test, a detailed ultrasound, or a physical exam after birth, these diagnostic tools provide a roadmap for your care team. Understanding the technical language in these reports can help you advocate for your child and prepare for the next steps.

Prenatal Screening and Imaging

During pregnancy, several tests are used to screen for and diagnose spina bifida. These tools work together to create a detailed picture of your baby’s development.

  • MSAFP (Maternal Serum Alpha-Fetoprotein): This is a blood test typically offered between 15 and 20 weeks of pregnancy [1]. It measures a protein made by the baby. If the baby has an open neural tube defect, this protein can leak into the amniotic fluid and then into the mother’s blood, causing high levels on the test [2].
  • High-Resolution Ultrasound: This is the primary tool for visualizing the spine. Radiologists look for specific “markers” in the baby’s anatomy:
    • The “Lemon Sign”: A slight inward curving of the frontal bones of the skull, which can be an early indicator of spina bifida [3].
    • The “Banana Sign”: An abnormal shape of the cerebellum (the part of the brain that controls balance), which may be pulled downward toward the spinal canal [4].
    • The Lesion Level: Doctors identify exactly which bone in the spine (vertebra) is affected. This is crucial because “lower” levels (closer to the tailbone) generally mean more preserved movement in the legs [5][6].
  • Fetal MRI: While ultrasound is excellent for screening, a fetal MRI provides much clearer details of the brain and spinal cord [7]. It is often used to confirm the diagnosis and to help families decide if they are candidates for surgery before the baby is born (in-utero repair) [8][9].

Key Findings in Imaging Reports

If you are looking at an imaging report, you may see terms related to how spina bifida affects the brain.

  • Chiari II Malformation: This occurs when the lower part of the brain is pulled down into the upper spinal canal [10]. It is very common in children with the “open” form of spina bifida [11].
  • Hydrocephalus and Ventriculomegaly: These terms describe the buildup of cerebrospinal fluid in the brain’s “ventricles” (fluid-filled spaces) [12]. If the fluid causes the ventricles to enlarge, it is called ventriculomegaly. If the pressure becomes too high, it is called hydrocephalus, which may require a small tube called a shunt to drain the fluid after birth [13][14].

Postnatal Diagnosis: The Newborn Exam

In some cases, especially with “closed” (occult) forms of spina bifida, the condition is not seen on prenatal scans and is only suspected after the baby is born [15].

Doctors look for cutaneous markers—telltale signs on the skin over the lower spine:

  • Sacral Dimples: Many babies have a small “simple” dimple near the tailbone that is perfectly normal. However, “atypical” dimples—those that are deep, large, or located higher up the back—may need further investigation [16][17].
  • Other Markers: A tuft of hair (hypertrichosis), a patch of discolored skin (hemangioma), or a fatty lump under the skin can also be signs of an underlying spinal issue [15][18].

Follow-up Screenings for Newborns

If a doctor finds a suspicious marker, they may order:

  1. Spinal Ultrasound: This is a quick, painless way to look at the spinal cord in infants under 6 months old, before the bones of the spine fully harden [7][16].
  2. Postnatal MRI: This is the “gold standard” for diagnosing tethered cord—a condition where the spinal cord is attached to surrounding tissues and cannot move freely as the child grows [19][20]. It provides the most detailed information for surgical planning [7].

Common questions in this guide

What do the lemon and banana signs mean on my prenatal ultrasound?
The lemon and banana signs are specific shapes seen in the baby's skull and brain during a prenatal ultrasound. They indicate changes in brain structure that are strongly associated with open spina bifida.
What does the lesion level mean for my baby?
The lesion level identifies exactly which vertebra on the spine is affected by the opening. A lower level on the spine, closer to the tailbone, generally means the child will have more preserved movement and function in their legs.
Does a sacral dimple mean my baby has spina bifida?
Many babies have simple, shallow sacral dimples near the tailbone that are completely normal. However, if a dimple is deep, large, or located higher up the back, doctors may order a spinal ultrasound to check for closed spina bifida or a tethered cord.
What is ventriculomegaly?
Ventriculomegaly is a buildup of cerebrospinal fluid that causes the fluid-filled spaces in the brain to enlarge. If the pressure from this fluid becomes too high, it develops into hydrocephalus, which may require a shunt to drain the fluid after birth.
Why would my doctor order a fetal MRI for spina bifida?
A fetal MRI provides highly detailed images of your baby's brain and spinal cord that ultrasounds might miss. It helps confirm the diagnosis, reveals the exact severity of the condition, and helps determine if you are a candidate for fetal surgery before birth.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.On our ultrasound report, what is the exact 'lesion level' (e.g., L3 or S1), and how does that affect future walking or bladder function?
  2. 2.Can you explain the 'lemon' and 'banana' signs on my scan and what they tell us about my baby's brain development?
  3. 3.Is there evidence of ventriculomegaly, and what is the current measurement of the ventricles?
  4. 4.If our baby has a sacral dimple, what specific features (like location or depth) make it 'atypical' or 'high-risk' enough to need an MRI?
  5. 5.Does the fetal MRI show any evidence of 'tectal beaking' or other signs of Chiari II malformation?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (20)
  1. 1

    Laboratory screening and diagnosis of open neural tube defects, 2019 revision: a technical standard of the American College of Medical Genetics and Genomics (ACMG).

    Palomaki GE, Bupp C, Gregg AR, et al.

    Genetics in medicine : official journal of the American College of Medical Genetics 2020; (22(3)):462-474 doi:10.1038/s41436-019-0681-0.

    PMID: 31700163
  2. 2

    Screening for Open Neural Tube Defects.

    Krantz DA, Hallahan TW, Carmichael JB

    Clinics in laboratory medicine 2016; (36(2)):401-6.

    PMID: 27235920
  3. 3

    [Prenatal diagnosis of neural tube defects: Correlation between prenatal and postnatal data].

    Matuszewski L, Perdriolle-Galet E, Clerc-Urmès I, et al.

    Journal of gynecology obstetrics and human reproduction 2017; (46(3)):291-296 doi:10.1016/j.jogoh.2016.10.009.

    PMID: 28403928
  4. 4

    Prenatal diagnosis of spina bifida: from intracranial translucency to intrauterine surgery.

    Sepulveda W, Wong AE, Sepulveda F, et al.

    Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery 2017; (33(7)):1083-1099 doi:10.1007/s00381-017-3445-7.

    PMID: 28593553
  5. 5

    Brain malformations and spina bifida.

    Fletcher JM, Kulesz PA

    Developmental medicine and child neurology 2021; (63(3)):244 doi:10.1111/dmcn.14745.

    PMID: 33236354
  6. 6

    Thalamic connectivity topography in newborns with spina bifida: association with neurological functional level but not developmental outcome at 2 years.

    Ji H, Payette K, Speckert A, et al.

    Cerebral cortex (New York, N.Y. : 1991) 2024; (34(1)) doi:10.1093/cercor/bhad438.

    PMID: 37991274
  7. 7

    Comparative diagnostic accuracy of ultrasound and magnetic resonance imaging for spinal dysraphism in infants: insights from a single-center study.

    Daqqaq TS

    Radiologie (Heidelberg, Germany) 2025; (65(Suppl 1)):93-99 doi:10.1007/s00117-025-01494-2.

    PMID: 40864245
  8. 8

    Impact of the cystic neural tube defects on fetal motor function in prenatal myelomeningocele repairs: A retrospective cohort study.

    Corroenne R, Sanz Cortes M, Johnson RM, et al.

    Prenatal diagnosis 2021; (41(8)):965-971 doi:10.1002/pd.5992.

    PMID: 34145612
  9. 9

    Magnetic Resonance Imaging Evaluation of Fetal Neural Tube Defects.

    Egloff A, Bulas D

    Seminars in ultrasound, CT, and MR 2015; (36(6)):487-500.

    PMID: 26614132
  10. 10

    Arnold-Chiari Malformation: Core Concepts.

    Fons K, Jnah AJ

    Neonatal network : NN 2021; (40(5)):313-320 doi:10.1891/11-T-704.

    PMID: 34518383
  11. 11

    Virtual navigation for the improvement of parents counseling and the planning of fetal endoscopic myelomeningocele repair.

    Werner H, Ribeiro G, Lopes J, et al.

    Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery 2021; (37(3)):969-972 doi:10.1007/s00381-020-04961-4.

    PMID: 33146768
  12. 12

    Myelomeningocele Versus Myelocele on Fetal MR Images: Are There Differences in Brain Findings?

    Nagaraj UD, Bierbrauer KS, Stevenson CB, et al.

    AJR. American journal of roentgenology 2018; (211(6)):1376-1380 doi:10.2214/AJR.18.20088.

    PMID: 30332293
  13. 13

    Detailed Analysis of Hydrocephalus and Hindbrain Herniation After Prenatal and Postnatal Myelomeningocele Closure: Report From a Single Institution.

    Flanders TM, Heuer GG, Madsen PJ, et al.

    Neurosurgery 2020; (86(5)):637-645 doi:10.1093/neuros/nyz302.

    PMID: 31432079
  14. 14

    Fetal Repair of Neural Tube Defects.

    Lee SY, Papanna R, Farmer D, Tsao K

    Clinics in perinatology 2022; (49(4)):835-848 doi:10.1016/j.clp.2022.06.004.

    PMID: 36328602
  15. 15

    Cutaneous Stigmata of the Spine: A Review of Indications for Imaging and Referral.

    Behbahani M, Lam SK, Bowman R

    Pediatric clinics of North America 2021; (68(4)):895-913 doi:10.1016/j.pcl.2021.04.017.

    PMID: 34247716
  16. 16

    Sacral dimple: clinical perspectives of lesions hidden beneath the skin.

    Eun J, Lee KS, Yang SH

    Clinical and experimental pediatrics 2026; (69(2)):103-113 doi:10.3345/cep.2025.01802.

    PMID: 41331294
  17. 17

    Screening for Spinal Dysraphisms in Newborns With Sacral Dimples.

    Wilson P, Hayes E, Barber A, Lohr J

    Clinical pediatrics 2016; (55(11)):1064-70 doi:10.1177/0009922816664061.

    PMID: 27554766
  18. 18

    Midline cutaneous anomalies of the craniospinal axis.

    Ren F, Bressler L, Pruitt L, et al.

    Journal of the American Academy of Dermatology 2023; (89(6)):1238-1244 doi:10.1016/j.jaad.2023.06.062.

    PMID: 37598328
  19. 19

    Closed spinal dysraphism: Think about it in the case of enuresis in children.

    Kessi EMCJ, Maslouhi K, Diallo ID, et al.

    Radiology case reports 2025; (20(10)):5255-5257 doi:10.1016/j.radcr.2025.06.114.

    PMID: 40791963
  20. 20

    Ultrasonography and magnetic resonance imaging evaluation of pediatric spinal anomalies.

    Dhingani DD, Boruah DK, Dutta HK, Gogoi RK

    Journal of pediatric neurosciences 2016; (11(3)):206-212 doi:10.4103/1817-1745.193374.

    PMID: 27857788

This page provides educational information about prenatal and postnatal spina bifida screening. It does not replace professional medical advice. Always discuss ultrasound, MRI, and blood test results directly with your maternal-fetal medicine specialist or pediatrician.

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