Are female fetuses more reactive when mother eats chocolate?

In response to the letter published in issue 27-01 -- Tranquilli AL, Lorenzi S, Buscicchio G, Di Tommaso M, Mazzanti L, Emanuelli M. Female fetuses are more reactive when mother eats chocolate. J Matern Fetal Neonatal Med. 2013.

We read the article by Tranquilli et al. with great interest [1]. Female fetuses were found to be more reactive when the mother ate chocolate and the investigators speculated about the innate gender difference for the effects of chocolate. While we believe the results have important consequences, there are some aspects which may be criticized.

In this interesting study, there was no sample size calculation or power analysis. Power analysis is a crucial part of a good research in order to detect an effect of a given size and without this, the study may be underpowered to reach the conclusion that female fetuses are more reactive than male fetuses after chocolate ingestion.

Secondly, the design of the study did not include a control group in which the pregnant patient does not receive chocolate. In our previous study [2] we have shown that control group for non-reactive non-stress test (NST) had 66.7% reactivity after 30 min and this was not statistically different from orange juice and chocolate groups [2]. We concluded that the reactivity after a non-reactive NST is independent from what you give or not give to the pregnant patient. If you just let the patient to sit for 30 min after a non-reactive NST, you may have similar percentage of reactive NST patterns when compared with patients who were given orange juice or chocolate. Female fetuses might have been more reactive even if their mothers ate nothing. That is why, a control group, which consists of pregnant patients with female and male fetuses, but do not consume chocolate would be ideal and gave more information on this topic.