Maternal dietary ratio of linoleic acid to alpha-linolenic acid during pregnancy has sex-specific effects on placental and fetal weights in the rat

BACKGROUND: Increased consumption of linoleic acid (LA, omega-6) in Western diets coupled with the pro-inflammatory and adipogenic properties of its derivatives has led to suggestions that fetal exposure to this dietary pattern could be contributing to the intergenerational cycle of obesity. METHOD: This study aimed to evaluate the effects of maternal consumption of a LA to alpha-linolenic acid (ALA) ratio similar to modern Western diets (9:1) compared to a lower ratio (1:1.5) on placental and fetal growth, and to determine any cumulative effects by feeding both diets at two total fat levels (18% vs 36% fat w/w). Female Wistar rats (n = 5–7/group) were assigned to one of the four experimental diets prior to mating until 20d of gestation. RESULTS: Fatty acid profiles of maternal and fetal blood and placental tissue at 20d gestation were different between dietary groups, and largely reflected dietary fatty acid composition. Female fetuses were heavier (2.98 ± 0.06 g vs 3.36 ± 0.07 g, P < 0.01) and male placental weight was increased (0.51 ± 0.02 g vs 0.58 ± 0.02 g, P < 0.05) in the low LA:ALA groups. Female fetuses of dams exposed to a 36% fat diet had a reduced relative liver weight irrespective of LA:ALA ratio (7.61 ± 0.22% vs 6.93 ± 0.19%, P < 0.05). These effects occurred in the absence of any effect of the dietary treatments on maternal bodyweight, fat deposition or expression of key lipogenic genes in maternal and fetal liver or maternal adipose tissue. CONCLUSION: These findings suggest that both the total fat content as well as the LA:ALA ratio of the maternal diet have sex-specific implications for the growth of the developing fetus.