Early pregnancy body mass index modifies the association of pre-pregnancy dietary patterns with serum polyunsaturated fatty acid concentrations throughout pregnancy in Brazilian women.

Dietary patterns (DPs) have been described as an important factor that may influence polyunsaturated fatty acid (PUFA) concentrations and body mass index (BMI) during pregnancy. We aim to evaluate the association between pre-pregnancy DPs and serum PUFA percentages throughout pregnancy considering early pregnancy BMI as a possible effect modifier. A prospective cohort of 154 pregnant women was followed (5th-13th, 20th-26th, and 30th-36th gestational weeks). Serum PUFA concentrations (total n-3 and total n-6, eicosapentaenoic + docosahexaenoic acids) were measured in each trimester and expressed as percentages. The n-6/n-3 ratio was calculated. Longitudinal linear mixed-effects models including interaction terms between DPs and early pregnancy BMI were employed. Serum PUFA percentages declined, whereas the n-6/n-3 ratio, monounsaturated, and saturated percentages increased throughout pregnancy for all BMI categories. Three pre-pregnancy DPs were identified by principal component analysis (common Brazilian, healthy, and processed). Overweight women with higher adherence to the common-Brazilian and to the healthy DPs presented reduced n-3 PUFA percentage and increased n-6 percentages and n-6/n-3 ratio compared to under or normal weight women. Obese women with higher adherence to the processed DP presented a more pronounced decrease of total n-3 percentage compared to under or normal weight women. Early pregnancy BMI modified the effect of pre-pregnancy DPs on PUFA profile throughout gestation. Higher adherence to the healthy pattern was associated with increased n-3 percentage, except for overweight women. Only for processed DP was the behaviour of PUFA the same for all BMI categories, showing a worse evolution profile, that is, increased n-6 and reduced n-3 fractions.