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Pregnant women with low weight can transfer more organochlorine pollutants into breastmilk

Some pollutants are known to accumulate in the body's fatty tissue. How does this affect pregnant women? there a link between weight gain and the transfer of pollutants to the newborn? A new study provides new data that can help the administration and health managers in their decision making.

A study led by Joan O. Grimalt and Mercè Garí, from the Institute of Environmental Diagnosis and Water Studies (IDAEA-CSIC), shows that there is a relationship between the presence of organochlorine compounds in breast milk and women's weight gain during pregnancy. The results of the study indicate that if women do not gain enough weight during pregnancy, they will transfer more pollutants to their babies during breastfeeding.

The organochlorine compounds analysed are fungicides and pesticides that were widely used during the 1950s and 1960s.

Although they were banned by the Stockholm Convention in 2001, their chemical stability and continued use, intentional or not, means that they are still found in many environments around the world, as well as in various tissues and fluids of the human body.

Up to 376 women from hospitals in Sabadell (Catalonia) and Guipúzcoa (Basque Country) took part in the study, in which the Public Health Department of Guipúzcoa and the Barcelona Health Institute (ISGlobal) also collaborated. Of these, 26% had low gestational weight gain. All of them provided samples of colostrum (first breast milk at the start of lactation) and blood serum. Six organochlorine compounds were analysed: hexachlorobenzene, lindane, several polychlorinated biphenyls and the group of DDT.

The work is consistent with other studies that have found that pregnant women who gain less weight transfer more pollutants to their babies through the placenta.

The results show that women who did not reach enough weight during gestation, as recommended by the US National Academy of Medicine (IOM), transferred a higher amount of these compounds in their colostrum.

The explanation lies in the fact that these contaminants are mostly found in fatty tissue, as they have a biochemical affinity for lipids.

If during pregnancy, women do not incorporate enough new fat through her diet, the fat previously accumulated in mother's body, in which these contaminants have been stored for years, is mobilised to other parts of her body, thus distributing the contaminants to the bloodstream, and from there to the colostrum.

Also through the placenta

These results are consistent with previous studies, which showed that mothers with lower gestational weight gain can transfer more contaminants through the placenta to their infants. The results of the new study are consistent with them.

Furthermore, as the study explains, toxic compounds with similar physical and chemical properties would behave similarly, and it would mean a higher mon-baby transmission in the case of mothers with low gestational weight gain.

This work shows that organochlorine pollutants are still present in the environment as well as in the human body, despite they were banned more than 20 years ago.

Gynaecologists and pregnant women should be informed on the desirability of an adequate weight gain during pregnancy. Although a too high a gestational weight gain can lead to complications at delivery due to an overly large foetus, low weight gain has the disadvantage of a higher pollutant transmission to the foetus and breast milk.

Reference article

Influence of gestational weight gain on the organochlorine pollution content of breast milk Joan O. Grimalt, Mercè Garí, Loreto Santa-Marina, Jesús Ibarluzea, Jordi Sunyer. Environmental Research, https://doi.org/10.1016/j.envres.2022.112783

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