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Reply to “methodological concerns in the exclusive human milk study”

Journal of Perinatology volume 41, pages 912–913 (2021)Cite this article

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We thank Dr Razak for his commentary “methodological concerns in the exclusive human milk study” and his careful attention to our article [1]. He has allowed us the opportunity to correct a couple of unfortunate misstatements. He is correct in pointing out that we “flipped” the odds ratio. We should have stated that the incidence of severe IVH/PVL was significantly higher in the non-EHM group as opposed to the EHM group (p = 0.012; OR = 2.7) after adjusting for antenatal steroids use and NEC. In the abstract, we also mistakenly stated that rate of NEC was higher in the EHM group; of course, the reverse was true.

We somewhat disagree, though, on the rationale for adjustment for NEC when assessing the association between EHM and severe IVH/PVL. Dr Razak suggests, on the one hand, that “NEC partially mediates the association between the EHM and PVL”. He then states that controlling for NEC would be inappropriate as it would partially close “the indirect causal path”. We suggest that whether to control (or not) for NEC depends on the purpose of the adjustment and also on the role attributed to NEC in studying the association between EHM and IVH/PVL. We viewed NEC as possibly a potential confounder since EHM can affect the incidence of NEC, and the latter may be associated (possibly indirectly) with IVH/PVL. Thus we wished to examine whether EHM effects the incidence of IVH/PVL at all, separate from its possible effects on the incidence of NEC. In our study we use logistic regression to assess this. In response to Dr Razak’s comment, we wish to present our data in a somewhat different manner which may provide greater clarity. We have taken our original data (Table 3 in our article) and have reanalyzed our data after eliminating all NEC cases (and their associated IVH/PVL) [1]. Thus, we have 121 neonates in the EHM cohort and 148 babies in the non-EHM cohort. The results are in Table 1 below. The data shows a significantly reduced incidence of severe IVH and/or PVL in the EHM cohort. This demonstrates that the effects of EHM on the incidence of severe IVH/PVL extend beyond the effect of EHM on NEC.

Table 1 Severe IVH and PVL in infants fed EHM or non-EHM diet after excluding NEC.
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References

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Authors and Affiliations

  1. Westchester Medical Center, Division of Newborn Medicine, Maria Fareri Children’s Hospital, Valhalla, NY, USA

    Amanda Rahman & Boriana Parvez

  2. Department of Pediatrics, Neonatal-Perinatal Medicine, Staten Island University Hospital, Staten Island, NY, USA

    Amanda Rahman

  3. New York Medical College, Division of Newborn Medicine, Maria Fareri Children’s Hospital at Westchester Medical Center, Valhalla, NY, USA

    Katherine Carome & Boriana Parvez

  4. Department of Pediatrics, Ann and Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL, USA

    Katherine Carome

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  1. Amanda Rahman
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  2. Katherine Carome
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  3. Boriana Parvez
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Correspondence to Amanda Rahman.

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Rahman, A., Carome, K. & Parvez, B. Reply to “methodological concerns in the exclusive human milk study”. J Perinatol 41, 912–913 (2021). https://doi.org/10.1038/s41372-021-00968-0

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