Authors’ reply re: Global inequities in dietary calcium intake during pregnancy: a systematic review and meta-analysis

CORMICK, GABRIELA; BELIZÁN, JOSÉ M; BETRÁN, ANA PILAR; BETRÁN, ANA PILAR; CIAPPONI, AGUSTÍN; CIAPPONI, AGUSTÍN; CORMICK, GABRIELA; BELIZÁN, JOSÉ M

BJOG-AN INTERNATIONAL JOURNAL OF OBSTETRICS AND GYNAECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2019 vol. 126

1470-0328

We deeply appreciate the interest and the careful analysis of the methodology of our paper addressed by Jiang et al. in their letter.1, 2 The concerns of the authors of this letter are about duplicate populations because there are two articles from the same author and country that have the same or similar number of participants.3-6 When performing this review, we were careful to detect duplications, and for this reason we discarded 57 articles from the search that showed repeated populations. The authors mentioned two included articles from Karras et al. in Greece, carried out in the same maternity unit.3, 4 Regardless that there are many similarities, like the same sample size, the data were collected in different periods of time that overlapped by 1 or 2 months and they showed different calcium intake. In the study conducted between February 2010 and March 2011, they report a calcium intake of 283 mg/day3 whereas in the study conducted from January 2011 to December 2011 they report a calcium intake of 786 mg/day.4 The later population is one in which 36 in 60 women received calcium supplements during pregnancy, in comparison with the sample showing lower intake, who received no calcium supplements during pregnancy. The other concern of the authors regards the articles from Kumar et al. in India.5, 6 These studies were performed in the same hospital and the data collection period overlapped by 1 year; however, one study was on vegetarian women5 and the other was a randomised controlled trial that did not require participants to be vegetarian as an exclusion criterion. We agree with the possibility that in this last case the information of some vegetarian women could have been duplicated in our estimates of calcium intake. We re‐ran the meta‐analysis excluding the study on vegetarian women5 and the calcium intake in pregnant women from high‐income countries (HICs) changed from 647.6 mg/day (95% CI 568.7?726.5 mg/day) to 655.3 mg/day (95% CI 574.1?736.6 mg/day).