Nitrous oxide in labour predicted newborn screening total homocysteine and is a potential risk factor for infant vitamin B12 deficiency

Abstract

Aim Risk factors for vitamin B12 deficiency in infants are not fully understood. The aim of the study was to assess predictors of total homocysteine and methylmalonic acid analysed in newborn screening dried blood spots. Methods In a Norwegian case control study, we analysed total homocysteine and methylmalonic acid in newborn screening dried blood spots of 86 infants clinically diagnosed with vitamin B12 deficiency during 2012–2018. Results were compared to 252 healthy infants and 400 dried blood spot controls. Medical records were reviewed, and mothers completed questionnaires. Results Both total homocysteine and methylmalonic acid were significantly higher on newborn screening dried blood spots in infants later clinically diagnosed with vitamin B12 deficiency than controls. Multiple regression analysis showed that the dose of nitrous oxide during labour was the strongest predictor for total homocysteine level in newborn screening dried blood spots for all infants, with larger effect in infants later clinically diagnosed with vitamin B12 deficiency than controls. Conclusion Nitrous oxide dose during labour was a predictor for total homocysteine and may impact the interpretation of total homocysteine analysis in newborn screening. Nitrous oxide is suggested as a contributing risk factor for infants prone to develop vitamin B12 deficiency.

Vitamin B12 Deficiency (Un-)Detected Using Newborn Screening in Norway

“…DBS methylmalonic acid (DBS MMA), DBS-total homocysteine (DBS tHcy) and DBS 2-methylcitrate (DBS MCA) were also analyzed in the original DBS. A combined analysis for second-tier tHcy, MMA and MCA was developed for DBS using an LC-MS/MS method adapted from Fu et al [ 28 ] and described in [ 29 ]. The method was implemented as a routine second-tier test for C3 and C3/C2 above cut-off during 2020.…”

“…Normal DBS tHcy, DBS MMA and DBS MCA percentiles were determined from assessments of 450 randomly selected DBS that were sampled and analyzed in batches in 2021. DBS from a selected group of 89 healthy newborns born between 2012 and 2018, who were sampled and matched for another study of B12 deficiency in infants, were also included as controls [ 29 ].…”

A Retrospective Evaluation of the Predictive Value of Newborn Screening for Vitamin B12 Deficiency in Symptomatic Infants Below 1 Year of Age

“…We recruited a cohort of healthy, age-matched infants, referred to as clinical controls, scheduled for postnatal clinical follow-up in 2018-2019 from the Postnatal and Neonatal Unit at Vestfold Hospital Trust, Norway [16]. Details on inclusion, background characteristics, clinical and biochemical findings have been published elsewhere [1,[15][16][17][18]. We also included NBS dried blood spot (DBS) controls, matched for date of birth, age in days, sex, hospital, birth weight and gestational age of the clinical cases and clinical controls, designated as matched NBS DBS controls.…”

“…The second-tier analyses were performed at the time of the standard NBS analyses for the unmatched controls. A combined method for second-tier analysis of tHcy, MMA and MCA in DBS was set up using an LC-MS/MS method described elsewhere [15], and systematically introduced as second-tier analysis for cystathionine β-synthase deficiency and methylmalonic-and propionic aciduria in 2020. Readings without a tHcy peak were considered unreliable and therefore excluded.…”

“…In Canada, 5% of women in fertile age has been found to have vitamin B12 deficiency [10]. Nitrous oxide (N 2 O), commonly used as pain relief in labor, accumulates in the fetus and is known to irreversibly inhibit methionine synthase by oxidizing the cobalt atom in a dose-response manner [11][12][13][14][15].…”