Altered materno-fetal transfer of 13C-polyunsaturated fatty acids in obese pregnant women

Background & aims: Maternal obesity at conception is considered a major predictor of offspring obesity. This could by driven at least in part by an altered placental fat transfer. However, the pathophysiological mechanisms involved are not fully understood. We investigated the in vivo materno-fetal transfer of fatty acids (FAs) in obese pregnant women using stable isotopes. Methods: Ten obese and ten normo-weight pregnant women (control) received orally a bolus of 13 C-labeled FAs 12 h before elective caesarean section: oleic acid ( 13 C-OA), linoleic acid ( 13 C-LA) and docosahexaenoic acid ( 13 C-DHA). Maternal blood samples were collected at −12 (basal), −8, −4, −2, 0 h relative to the time of cesarean section. At the time of birth, arterial and venous cord bloods as well as placental tissue were collected. FAs composition was determined by gas-liquid chromatography and isotopic enrichment by gas chromatography-combustion-isotope ratio mass spectrometry. Results: Maternal plasma insulin and placental weight tended to higher values in obese pregnant women although they did not present serum hyperlipidemia. Higher concentrations of 13 C-LA and 13 C-DHA were found in non-esterified FAs fraction in maternal plasma of obese mothers. The ratio of placental uptake for 13 C-LA and 13 C-DHA was lower in obese women compared to normal weight pointing toward a limited capacity of FA placental transfer, especially of essential FAs. Maternal insulin was associated to this lower placenta/maternal plasma ratio for both 13 C-LA (R = −0.563, P = 0.012) and 13 C-DHA (R = −0.478, P = 0.033). In addition, the ratio cord/maternal plasma of 13 C-LA was significantly lower in obese women compared to controls. Conclusions: In conclusion, obese mothers without hyperlipidemia showed a reduced materno-fetal transfer of polyunsaturated FAs which could affect fetal development. This affect dietary recommendation for obese pregnant women. Trial registry number: ISRCTN69794527