Diet during pregnancy and levels of maternal pregnancy hormones in relation to the risk of breast cancer in the offspring.

Birth weight is positively associated with the risk of breast cancer in the offspring and the underlying process is likely to involve the pregnancy endocrine milieu. We have examined the association of diet and related factors during pregnancy with the levels (at the 16th and 27th gestational week) of maternal pregnancy oestradiol, oestriol, sex hormone-binding globulin (SHBG), progesterone and prolactin, in a cohort of 270 Caucasian women who delivered in a major hospital in Boston, USA. Oestradiol and oestriol were not strongly associated with any of the diet-related variables, but SHBG was significantly and consistently related inversely to pre-pregnancy body mass index and weight gain during pregnancy, and positively to vegetable and pulses intake. Pregnancy progesterone was associated positively with alcohol and inversely with polyunsaturated lipid and vitamin B12 intake, whereas pregnancy prolactin was inversely associated with cereal consumption. If the pregnancy hormones studied are indeed involved in the intra-uterine origin of breast cancer, these findings, if confirmed, would focus dietary advice to pregnant women, with a view to reducing the risk of breast cancer in the offspring, towards avoidance of excess energy intake and an emphasis on plant foods. This advice does not contradict current dietary advice on prudent diet during pregnancy and throughout life.