We welcome the valuable comments on the article ‘A Correlative Study of Maternal Haemoglobin and Birth Weight” . We would like to respond to the comments as under:
In our study 500 consecutive pregnant mothers who satisfied the inclusion and exclusion criteria and resulted in live births (as primary outcome of interest was birth weight) were included from each of the two centres. By ‘cross sectional population” it was meant to indicate that a cross section of pregnant woman fulfilling the elgibility criteria were followed prospectively till the time of livebirth. It was not a cross sectional study in the sense (as implied in the letter to editor) that a single evaluation of a cross section of pregnant women was carried out only once.
(i) We agree that randomization is a statistical procedure used in interventional study for eliminating bias by ensuring that investigator has no control over allocation of participants to study and control group. In the present study there was no control group. Selecting consecutive pregnant women fulfilling predefined eligibility criteria amounted to a random selection and eliminated any bias in selection of patients.
(ii) There was no stratified randomization in the study. The women were stratified at the time of analysis in to various groups based on the socioeconomic status to determine the influence of socioeconomic, status on haemoglobin levels and birth weight.
(iii) As explained above, it was a prospective study of pregnant mothers who went on to deliver a live baby and not a case control study.
A medical illness in mother constituted an exclusion criterion. We agree that multiple pregnancy and shorter interpregnancy interval (< 2 years) are also known to influence the birth weight.
Haemoglobin estimation was done by cyanmeth haemoglobin method, a standardised method for haemoglobin estimation, in both the hospitals. The primary objective of the study was to see the correlation between maternal haemoglobin levels and birth weight in different socioeconomic groups and not maternal anaemia and birthweight. A haemoglobin value of less than 11 gm/dl at any time during gestation was labelled as anaemia. This study showed a significant inverse relationship of maternal haemoglobin concentration to birth weight, in agreement with the hypothesis that a higher blood viscosity with rising haemoglobin levels is responsible for sub optimal placental perfusion and decreased delivery of nutrients to the foetus
1. RaghuRaman TS, Parimala V, Bhulla M, Venkateshwar V, Iyengar A. A correlative study of maternal haemoglobin and birth weight. MJAH. 2001;57:110–113.
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