Regarding the association between iron status during pregnancy and congenital heart defects

We are delighted to read the comments about our recent publication [ [1] Yang J. Kang Y. Cheng Y. et al. Iron intake and iron status during pregnancy and risk of congenital heart defects: a case-control study. Int. J. Cardiol. 2020; 301: 74-79 Abstract Full Text Full Text PDF PubMed Scopus (9) Google Scholar ]. Our study mainly focused on different maternal sources and types of iron intakes and congenital heart defects (CHDs). We also observed that maternal iron status before delivery was low among mothers whose fetuses had CHDs, which was consistent with maternal lower iron intake in the cases in our study. It was true that we did not observe significant differences in neonatal iron biomarkers between the cases and controls, although the SF value seemed to be lower among the CHDs fetuses. This situation may be due to the fact that fetuses win the competition of iron in pregnancy [ [2] Rasmussen K.M. Stoltzfus R.J. New evidence that iron supplementation during pregnancy improves birth weight: new scientific questions. Am. J. Clin. Nutr. 2003; 78: 673-674 Crossref PubMed Scopus (39) Google Scholar ]. However, we cannot exclude the possibility of CHDs fetuses having lower iron status during the critical period of cardiac development in the 3rd-8th week of gestation. It is regretful that we cannot obtain the information about iron nutritional metabolism during the early stage of pregnancy because of the case control design. It is important to further explore the mechanism through prospective cohort study.