RE: "PRETERM BIRTH AND LICORICE CONSUMPTION DURING PREGNANCY"

Jenny Hughes, Sarah Sellick, Rachel King and Iain J. Robbé

College of Medicine, University of Wales, Heath Park, Cardiff CF14 4XN, Wales

We read with interest the paper on preterm birth and licorice consumption during pregnancy in which Strandberg et al. (1) reported that heavy intake of glycyrrhizin (licorice) is associated with shorter gestation.

However, we have some concerns regarding the methods of the study. The questionnaire used in this study was similar to that used in Strandberg et al.’s previous cross-sectional study (2) on licorice and birth outcome. In the original study, it was found that glycyrrhizin intake was not connected with a number of lifestyle factors, body mass index, or blood pressure, and therefore questions on these factors were omitted from the questionnaire for the present study. However, this was not a nested case-control study, because it was carried out in a different population sample, and we wonder whether it can rightly be assumed that these factors are not causally related to preterm birth in this population. The reason given for the omission in this study was to reduce the size of the questionnaire in order to improve compliance, although compliance was not reported to be a problem in the original study.

Integral to the study is the gestational age of the infant, but the methods used for consistent determination of gestational age are unclear. Ultrasound examination may be used to assess fetal age in a number of ways—for example, head circumference or humerus length. In the previous study (2), estimates of gestational age were obtained either from ultrasound measurements of biparietal diameter or from the mother’s self-report of the last menstrual period. It was not confirmed in the present study that the methods of measurement were consistent for all women.

There is also an issue about the selection of controls, because the criterion appears to be women who had given birth to full-term babies, and no further criteria for their selection are mentioned. Cases were statistically significantly younger, and therefore an analysis of odds ratios according to specific age groups may be valuable.

The authors recognize the limitation of retrospective collection of data regarding licorice consumption. Further validation from a second source, such as the woman’s partner, might be valuable in determining more accurately a woman’s licorice consumption. In addition, different types of licorice may contain different quantities of glycyrrhizin, a fact that may not have been taken into account when Strandberg et al. calculated glycyrrhizin intake.

REFERENCES

  1. Strandberg TE, Andersson S, Järvenpää A-L, et al. Preterm birth and licorice consumption during pregnancy. Am J Epidemiol 2002;156:803–5.[Abstract/Free Full Text]
  2. Strandberg TE, Järvenpää A-L, Vanhanen H, et al. Birth outcome in relation to licorice consumption during pregnancy. Am J Epidemiol 2001;153:1085–8.[Abstract/Free Full Text]




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