Antibodies in Newborn Cord Blood Raise Questions but Rarely Signal Disease in First Year

Every newborn arrives carrying a molecular snapshot of the maternal immune system. Antibodies cross the placenta in late pregnancy, providing the infant with passive protection against infections the mother has already encountered. But some of those antibodies are not so benign in reputation: antinuclear antibodies, or ANAs, are the classic laboratory signature of autoimmune diseases such as lupus, and their presence in a baby’s blood has long prompted worry among clinicians. A new prospective cohort study from Tehran University of Medical Sciences, published in BMC Pediatrics, now offers one of the most detailed pictures yet of what ANA reactivity in cord blood actually means for healthy-appearing newborns during their first year of life, and the answer is largely reassuring, though the researchers themselves stress that the picture remains incomplete.

The study team, led by Mehrnaz Adib and Payman Sadeghi, enrolled 171 neonates between March 2023 and March 2024 at a single center. Crucially, they deliberately excluded babies whose mothers had active or newly diagnosed autoimmune disease, or who had experienced a disease flare during pregnancy. That design choice is what makes the study distinctive: most existing knowledge about neonatal ANA positivity comes from high-risk pregnancies where mothers have known conditions such as lupus or Sjögren’s syndrome, and where antibodies like anti-Ro/SSA can cause congenital heart block and neonatal lupus rashes. By focusing on a clinically lower-risk population, the researchers asked a more fundamental question: how often does cord blood from apparently unremarkable pregnancies test positive for antinuclear antibodies, and does that positivity translate into any detectable illness?

The technical backbone of the study was the indirect immunofluorescence assay, or ANA-IFA, performed on human epithelial type 2, or HEp-2, cells. This method remains the gold standard for ANA detection because it exposes the patient’s serum to whole cells and lets trained observers see exactly where fluorescently labeled antibodies bind within the nucleus. The assay is broad by design; it detects reactivity against many nuclear antigens at once, which makes it sensitive but not specific for any particular disease. Out of 171 cord-blood samples, 26 came back positive, a prevalence of 15.2 percent, with an exact 95 percent confidence interval ranging from 10.2 to 21.5 percent. In other words, roughly one in six newborns in this low-risk cohort carried detectable antinuclear reactivity at birth.

That number alone is striking, but the researchers went further. Each ANA-IFA-positive infant was then subjected to a multiparameter antigen-specific antibody panel, a line-immunoassay approach that probes for reactivity against individual molecular targets. Only four of the 26 positive infants, or 15.4 percent, showed reactivity on this finer-grained panel. All four carried antibodies against double-stranded DNA, a target classically associated with systemic lupus erythematosus. Two also had anti-histone antibodies, and single infants showed reactivity against anti-nucleosome, anti-Jo-1, and anti-Ro52. Notably, none of the infants had reactivity against Ro60 or La/SSB, the two antigens most tightly linked to congenital heart block and neonatal lupus when transferred across the placenta. The absence of those particular specificities is perhaps the single most clinically comforting detail in the entire dataset.

All 26 ANA-IFA-positive infants then underwent a protocol-driven evaluation that most newborn screening programs would consider exhaustive. It included hematologic assessment with complete blood counts, liver enzyme measurement, electrocardiography, echocardiography, and structured clinical examination, repeated through the first 12 months of life. The results were remarkably benign. Four infants showed transient elevations in liver enzymes, specifically alanine and aspartate aminotransferases, but these abnormalities normalized within a single month and were not accompanied by any other signs of disease. Beyond that, no clinically relevant autoimmune manifestations were detected in any of the 26 positive infants, giving a rate of zero out of 26, with an exact 95 percent confidence interval of 0.0 to 13.2 percent. Hearts were structurally normal on echocardiography, conduction was normal on electrocardiography, and blood counts stayed within expected ranges.

The 145 ANA-IFA-negative infants received routine clinical follow-up, with investigations ordered only when symptoms warranted. None was recorded as developing autoimmune manifestations during the first year, but the authors are careful to acknowledge an important asymmetry in their design: because the negative group did not undergo systematic laboratory and cardiac screening, subclinical abnormalities in that group cannot be formally excluded. This differential outcome ascertainment, where positive infants were scrutinized far more intensively than negative ones, is a standard feature of such exploratory designs but limits how confidently the two groups can be compared. It is one of several caveats the researchers list when explaining why their findings cannot yet be turned into firm risk estimates.

The maternal side of the equation adds another layer of complexity. Mothers of the 26 positive infants underwent ANA-IFA testing themselves, and three of the 26 came back positive. Intriguingly, all three of those mothers had infants with antigen-specific panel reactivity, suggesting some degree of mother-to-infant concordance in antibody profiles, exactly what one would expect if placental transfer were the source of the cord-blood signal. However, antigen-specific testing of the mothers was incomplete, which prevented the team from performing a comprehensive concordance analysis. Without paired, complete maternal and neonatal panels, it remains impossible to say definitively whether every cord-blood ANA reflects passive maternal transfer, fetal immune activity, or some mixture of both. The authors also note that limited run-level assay documentation constrains the interpretability of individual results.

What, then, should clinicians and anxious parents take away from this work? The authors are explicit: these findings do not support routine ANA-IFA testing of asymptomatic neonates, and they do not justify any change to established surveillance protocols for babies with confirmed maternal anti-Ro/SSA or anti-La/SSB exposure. The reason is straightforward. Cord-blood ANA positivity in a low-risk population turns out to be relatively frequent, roughly 15 percent, but almost entirely nonspecific, and in this cohort it carried no measurable clinical consequence within the first year. Screening every newborn would therefore generate a substantial number of positive results, trigger extensive and costly workups, and create parental anxiety, all in pursuit of a signal that, on current evidence, rarely means anything. The transient liver enzyme elevations seen in four infants resolved without intervention and did not correspond to any antigen-specific pattern of obvious concern.

The study’s limitations are candidly enumerated and worth understanding. Beyond the differential ascertainment between positive and negative infants, the sample size of 171, while respectable for an exploratory single-center cohort, is too small to detect rare outcomes such as congenital heart block, which occurs in only a small fraction of anti-Ro-exposed pregnancies even in high-risk populations. The single-center design means the findings may not generalize to populations with different genetic backgrounds, referral patterns, or assay practices. And the twelve-month follow-up window, though it covers the period when neonatal lupus manifestations typically appear, cannot speak to longer-term risks of autoimmunity that might emerge in childhood or later.

For that reason, the research team calls for larger multicenter studies with paired maternal-neonatal testing, uniform assessment protocols, documented assay runs, serial antibody measurements over time, and follow-up extending well beyond infancy. Such work would settle whether the 15 percent of newborns with cord-blood ANA reactivity represent a truly silent majority whose antibodies simply fade as maternal immunoglobulin is catabolized over the first months of life, or whether a small subset harbors a subtle signal that only longer observation can reveal. Until then, this study provides a valuable baseline: in babies born without any hint of maternal autoimmune disease, antinuclear antibodies in cord blood are common, their antigen-specific signatures are uncommon, and clinically meaningful illness in the first year of life appears to be vanishingly rare. The placenta, it seems, delivers far more reassurance than alarm.

Subject of Research: Cord-blood antinuclear antibody positivity and first-year clinical outcomes in newborns without maternal autoimmune disease

Article Title: Cord-blood ANA-IFA positivity and first-year clinical findings in a selected lower-risk population: an exploratory prospective cohort study

Article References: Adib, M., Sheykhian, T., Assari, R., Alimadad Tafreshi, A., Ashkboos, K., Raeeskarami, S. R., Ziaee, V., Habibi, A., & Sadeghi, P. (2026). Cord-blood ANA-IFA positivity and first-year clinical findings in a selected lower-risk population: an exploratory prospective cohort study. BMC Pediatrics. https://doi.org/10.1186/s12887-026-07735-0

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07735-0

Keywords: antinuclear antibodies, cord blood, neonates, autoimmunity, ANA-IFA, HEp-2 cells, anti-dsDNA, neonatal lupus, anti-Ro/SSA, cohort study, pediatrics, placental antibody transfer