There have been numerous studies showing how olive oil affects pregnancy. In a recent study published in the journal Nutrition research, evidence has been collected for its effects on fetal maternal outcomes. The results are interesting, suggesting a protective effect on these outcomes.
Study: Olive oil consumption confers protective effects on maternal-fetal outcomes: A systematic review of the evidence. Image credit: Zhuravlev Andrey / Shutterstock
Nutrition plays a vital role in a pregnant woman’s health and the outcome of her pregnancy. Olive oil, an integral part of the Mediterranean diet (MD), is a healthy source of monounsaturated fatty acids (MUFAs) and phytochemicals such as polyphenols that promote favorable outcomes. Additionally, olive oil is linked to lower levels of adverse outcomes such as gestational diabetes mellitus (GDM), preeclampsia, and small for gestational age (SGA) or large for gestational age (LGA) infants.
There are various grades of olive oil, depending on the production method, nutritional content, taste and smell. These include virgin olive oil (VOO) and extra virgin olive oil (EVOO), the latter being the higher grade with evidence supporting its benefit as part of a cardioprotective protocol. It may be due to its antioxidant content and anti-inflammatory and anticancer properties.
The current review included nine studies from Spain, Denmark, Italy, the United Kingdom and Argentina. Some were so small that they included only 30 subjects, while the largest numbered over 35,000 women. All were from the period between 2008 and 2020.
These studies were interventional or randomized controlled trials (RCTs), while others were observational (case-control or cohort studies). One fifth were described as good quality, the rest as moderate quality.
Fetomaternal outcomes measured included SGA and LGA, preterm delivery, preeclampsia, and cardiovascular risk.
What did the study show?
Several studies have shown a significant reduction in SGA with EVOO supplementation compared to controls who restricted dietary fat intake. Regarding VOO intake, one study showed an increased risk of SGA, while two found no difference between EVOO or control groups.
Three RCTs concluded that EVOO supplementation reduced LGA rates, while one showed no difference in total neonatal complications. Similarly, two showed no significant association between olive oil and the risk of prematurity, one an RCT and the other a large prospective cohort study. However, another RCT showed a reduced risk of prematurity with EVOO supplementation.
This intervention also showed an association with a reduced risk of GDM in two studies, but another found no difference. Overall, the latter study failed to find a link between the risk of pregnancy complications overall, but did show an association with reduced pregnancy weight gain, which might indirectly increase the risk of pre-eclampsia. However, another paper contradicted this finding, showing that EVOO supplementation reduces risk.
Favorable cardiovascular effects in pregnancy and postpartum have also been observed in association with EVOO supplementation. This included a drop in triglyceride levels, possibly through modulation of transcriptional processes by the phenols and hydroxytyrosol in EVOO.
What are the implications?
The results of this study show that EVOO, in particular, and olive oil, in general, are associated with a reduced risk of maternal and fetal effects, including pre-eclampsia, GDM, SGA, and LGA. “To our knowledge, no systematic review summarizing the evidence on olive oil consumption and maternal-fetal outcomes has been performed.”
SGA is a marker of increased risk of adverse fetal outcomes, while LGA increases the risk of birth complications. Both have been shown to be reduced in association with EVOO intake, while an SGA study showed the same association with VOO intake.
Similarly, GDM and prematurity are linked to adverse fetal outcomes, both acute and chronic. Both were reduced results in one or more of the interventional studies. The antidiabetic effect could be due to the activity of polyphenols in EVOO as these compounds increase insulin sensitivity. However, more studies are needed as one researcher has reported an association between olive oil consumption and reduced weight gain, which may increase the risk of pre-eclampsia and SGA.
The reduced risk of pre-eclampsia reported by some studies may be due to the rich antioxidant and phenolic content of EVOO. The intervention in the only study that did not show such a benefit may have been performed too late to observe effects, because healthy placental invasion and remodeling, a crucial step in the development of the normal placenta and fetus, occurs during the first trimester of pregnancy.
This study is very early, with significant heterogeneity in many areas. “More studies focusing on the impact of olive oil consumption on reducing the possibility of adverse maternal-fetal outcomes are still neededHowever, the results suggest the value of olive oil consumption during pregnancy in relation to the reduction of the risk of SGA and LGA and of cardiovascular events, pre-eclampsia and GDM.