According to data provided by the Brazilian Ministry of Health (MH), approximately 21% of all live births in 2007 were born of adolescents . Pregnancy in this age group has been identified as a public health problem in Brazil and other countries, mainly because of possible adverse outcomes for both mother and child . In this study we asked if there are differences between the fatty acid profile in maternal and fetal biological compartments of adolescent and adult mothers and if there are relationship between this profile and the growth parameters of newborns in Brazilian pregnant woman.
A large percentage of the pregnant adolescents and adults evaluated had at least six prenatal medical visits, meeting the recommendations of the MH . This may have contributed to the greater proportion of newborns with adequate anthropometric nutritional status at birth in both age groups, confirming the positive association between quality of prenatal care and good outcome for the newborns as previously proposed in others studies [20, 24–26].
It has been reported that the maternal and fetal fatty acid status varies widely and is influenced by the mother’s dietary lipid intake . However, we found that relative concentrations of EFA in the maternal and umbilical cord plasma of both adolescents and adults were equivalent to those observed by Pankiewicz et al. , which were also identified for total lipids in the maternal and umbilical cord plasma of mothers.
We observed lower concentrations of LA and ALA and greater proportions of AA, EPA and DHA in the umbilical cord plasma than the maternal plasma in both age groups. These findings are consistent with the results of most previous studies which had also evaluated relative concentrations of FAs in these biological compartments [27–30]. These differences could be accounted for the presence of the placental membrane proteins which boost LC-PUFA uptake in such a way that these fatty acids are transported more efficiently than the shorter-chain variety . The existence of a specific transport system for fatty acids, which includes multiple proteins, facilitates the preferential transport of LC-PUFAs via the placenta and proves to be the mechanism that allows the needs of the fetus to be met .
In our study the proportion of SFA was significantly higher in the umbilical cord plasma than in the maternal plasma. This is in agreement with a previous study . The intense fetal lipogenesis which is reflected in the active synthesis of SFA  could provide the biochemical basis for these results.
Elias & Innis  found that dietary t FA intake related significantly and positively to t FA concentrations in the plasma of pregnant women. In addition, these authors found a significant relationship in the proportions of this fatty acid in maternal plasma and that of the umbilical cord. These findings are consistent with our results, which revealed similar concentrations of t FAs in the maternal and fetal plasma of the adult group. Additionally, other authors suggest that placental transfer of t FAs occurs selectively, because they are found in a greater percentage in the maternal plasma than the umbilical cord plasma [33, 35], which is in agreement with our results for the adolescent mothers.
Both the maternal plasma and the umbilical plasma of the adolescents presented higher proportions of AA when compared to the adults. We could not find similar results in existing literature; however, one can surmise that distinct dietary intake patterns may exist between the different groups. On the other hand, considering the fundamental role that AA plays in promoting growth during the fetal and postnatal period , the assumption can be made that the difference found in levels of this LC-PUFA between age groups could be due to the adolescents’ stage of growth and development. Indeed, this hypothesis demands further research.
Examining the umbilical cord plasma, we found that EPA content was higher in the adults than in the adolescents. These results suggest that, comparatively, the higher AA status of the adolescents may affect mother-fetal n-3 LC-PUFA transfer, contributing to the lesser proportion of EPA in the umbilical cord plasma of this age group . Previous report had pointed out that despite the scarcity of information regarding the impact of pregnancy and lactation on EFA and LC-PUFA status in adolescents, these two physiological situations may affect the status of these fatty acids differently in adults and adolescents .
With regard to the correlations between fatty acids in the maternal plasma of adolescents and adults, we found that total t FA and SFA were inversely correlated to relative concentrations of LA and to total EFA and n-6 PUFA levels. However, total t FA and SFA correlated positively with each other. These results can be justified by the mother’s habitual consumption of dietary sources of these fatty acids . An increase in consumption of processed products and fast food, which carry elevated levels of SFAs and t FAs, is generally accompanied by a reduction in consumption of n-6 and n-3 FAs food sources . In addition, a high intake of t FAs may alter maternal LC-PUFA status by reducing synthesis of AA, EPA and DHA fatty acids, especially by inhibiting the ∆6 desaturase enzyme, decreasing availability of these fatty acids to the fetus and, thus, compromising intrauterine development . Proper nutritional guidance during the prenatal stage could be a strategy to overcome the potential metabolic harms of these poor dietary practices .
Analysis of relative FA levels in the total lipids of the adolescent maternal plasma further revealed a negative correlation between LA and EPA proportions. In this regard, it is noteworthy that the ∆5 and ∆6 desaturase enzymes that act on PUFA desaturation have a greater affinity with the more unsaturated substrates, i.e., the n-3 family, followed by the n-6 and n-9 families. However, an increase in LA availability for these enzymes may impair desaturation of ALA to EPA and to DHA .
The standard diet of pregnant adolescents and adults in Brazil shows a prevalence of n-6 series fatty acid food sources, like vegetable oils, mainly soy oil, as opposed to n-3 sources, like fish and fish oil, resulting in a high n-6/n-3 ratio in their diet [37, 40].
Consistent with the inhibitory effect of t FA, as well as the fact that concentrations of this fatty acid in the fetal plasma are determined by maternal diet, a negative correlation was found between total t FA and total EFA and n-6 PUFA in the umbilical cord plasma of the adolescents, following the pattern of the maternal plasma. In the case of the cord plasma of the adult mothers, total t FA was shown to be inversely associated with AA and total n-6 PUFA, also similar to the maternal plasma of this group. Elias & Innis  observed an inverse relationship between dietary t FA and AA in the cholesterol esters of the umbilical cord plasma, as well as between t FA and DHA in the triacylglycerols, also in the umbilical cord plasma. It has been reported that trans isomers hamper placental transfer of LC-PUFA as they compete for the fatty acid-binding protein of the placental plasma membrane (FABPpm), lowering the fetal LC-PUFA status .
Our results do not indicate that t FAs interfere with the growth parameters of the newborn. These findings are consistent with data from previous studies which do not found an association between trans isomers and restricted intrauterine growth [12, 13, 29]. However, regarding n-3 LC-PUFA series, the relative concentration of DHA in the plasma of the adolescents associated positively with the weight and head circumference of the newborns. Recently, another study carried out by our group  found a positive and significant association between total n-3 PUFA in maternal milk and weight and length gain in preterm babies. This suggests that n-3 fatty acids have a greater influence on the proper development of the newborn, especially in situations of greater nutritional risk, like adolescent pregnancy and preterm birth.