INMA: “Weight gain during pregnancy and infant contamination”


All babies come into the world with a load of pollutants that comes from those accumulated in their mother’s body. It has been observed that, in addition to the maternal contamination load, one of the factors that influences this transfer is gestational weight gain. In an article published this year in Environmental Research by IDAEA-CSIC, ISGlobal and Biodonostia [1], it is described that in cases of low weight gain, a higher concentration of organochlorine contaminants is found in colostrum. The recommended weight gain is that indicated by the US Institute of Medicine (IOM) [2] and depends on the body mass index at the beginning of pregnancy. These are values of 12.6-18 kg, 11.25-15.75 kg, 6.75-11.25 kg and 4.94-9.0 kg of weight gain throughout pregnancy for mothers with a low, normal, overweight or obese index, respectively.

The described study has been conducted on the INMA (Childhood and Environment) cohort (reference hospitals of Sabadell and Gipúzcoa), where 376 paired samples of maternal venous blood and colostrum (initial breast milk after childbirth) were collected. Gestational weight gain was calculated using several different criteria that did not lead to significant changes in the statistical significance of the results. Individual and socioeconomic data of the mothers (educational level, social class, tobacco consumption, previous breastfeeding, place of birth) were also collected to eliminate possible confounding factors in the dependence of this weight gain.

The concentrations of the organohalogen compounds in the studied mothers were comparable to the usual ones in other populations of uncontaminated areas in equivalent times. Both in the case of the concentrations of organohalogen compounds in cord blood and colostrum, it was observed, in general, that the lower the weight increase, the higher the concentrations of these compounds were found, specifically polychlorobiphenyls, and 4,4′-DDE , which is a metabolite of DDT. The use of these compounds has long been banned, but they are still present in virtually all humans due to their persistence.

The means of the proportions of organohalogen compounds in colostrum:serum correlated significantly with physical-chemical properties such as the octanol-water partition coefficient (Kow), the higher the coefficient, the greater the relative amount in colostrum. This fact is consistent with changes in fat levels during pregnancy that influence the mobilization of these pollutants.

Other properties such as molecular weight also showed remarkable consistency with the mean ratio of organohalogen compounds in the colostrum:serum ratio. This suggests that the molecular size can also modify the transport capacity of these pollutants due to the permeability of the membranes.

The results of this study indicate that gestational weight gain influences the accumulation of organohalogen compounds in colostrum. The IOM recommendations for this weight gain may have clinical value in primary care because they provide guidance for reducing concentrations of organohalogen compounds in infants.

– Grimalt JO, Garí M, Santa-Marina L, Ibarluzea J, Sunyer J. Influence of gestational weight gain on the organochlorine pollution content of breast milk. Environ Res. 2022 Jun;209:112783.
Link to the scientific article:
– IOM.