Fat intake recommendations before, during and after pregnancy

VIDEO 9

Distinct biological functions of fat (e.g. fats as energy source or structural component), and the timing of exposure (e.g. fetal life, infancy or adulthood), determine related health outcomes. These outcomes can be suboptimal as a result of either too low or excessive fat intake. Total fat intake should comprise 20–35% of daily calories, similar to that for non-pregnant women. One of the most actively investigated research areas concerns the effects of polyunsaturated fatty acid intake during pregnancy and infancy in relation to a wide range of pregnancy and birth outcomes, infant neurodevelopment and various long-term outcomes.

Maternal nutrition and lifestyle are important determinants of intrauterine growth and infant health both in the short and long term and into adulthood. Maternal preconception predictors of reproductive outcome are well known. Maternal BMI is a key determinant of pregnancy outcome, as higher body fat levels are associated with increased inflammation, which in turn is linked to a greater risk of major pregnancy-related complications. Moreover, maternal diet and nutritional status are key predictors of pregnancy outcome, as they are associated with intake of essential nutrients, such as micronutrients (vitamins and minerals) and omega-3 fatty acids. The proportion of macronutrients required during pregnancy does not change, however, the type does. In the case of fat, a pregnant woman should aim to have fewer saturated fats and more essential long chain fatty acids, including omega-3 and omega-6 fatty acids and, in particular, their precursors, linoleic acid (LA), for the omega-6 arachidonic acid (ARA), and alpha-linolenic acid (ALA) for the omega-3 DHA. Due to substrate competition in the metabolic pathway, high levels of omega-6 fatty acids can reduce the conversion of ALA to DHA, potentially leading to insufficient DHA levels.

A biomagnification process occurs in the placenta, resulting in higher concentrations of long-chain polyunsaturated fatty acids (LC-PUFAs), such as ARA and DHA, in the fetal compared to the maternal circulation.

There have been many observational studies correlating maternal intake of fish, the main food containing omega 3 and therefore DHA, and pregnancy duration. Maternal blood analysis as early as in the first trimester of pregnancy, has shown DHA levels to correlate with embryonic length and volume, indicating that the mother’s diet, in particular, intake of fish, regulates embryo growth in the early stages of pregnancy.

DHA is necessary for fetal brain growth in the final months of pregnancy, with data showing an exponential increase in the DHA content of the fetal brain in the second half of pregnancy. Studies have investigated the effects of omega3/DHA supplementation on pregnancy outcomes, showing a significant effect on pregnancy prolongation and prevention of preterm birth (PTB), both in general (decrease by 11%) and of early preterm birth (decrease by 42%).

In recent years, two independent well-powered studies have shown that women with low baseline DHA status or intake benefit most from high doses of DHA supplementation¹,². These doses were as high as 1000 mg/day and, in the low baseline DHA status group, the decrease in early preterm birth reached 51%.

There are many plausible physiological mechanisms for DHA or DHA + EPA (eicosapentaenoic acid) to reduce PTB and early PTB. These include effects on eicosanoids involved in parturition, electrical activity of the myometrium, regulation of oxytocin signaling, effects on inflammatory pathways switching to a less pro-oxidant status, as well effects on reducing maternal stress, a known risk factor for PTB.

A practical guideline supported by several scientific societies was published in 2024, providing recommendations on general intake of DHA and EPA before and during pregnancy³. Notably, no safety concern of DHA intake up to 1000 mg/day was observed. This guideline stated that women of childbearing age should aim to obtain a regular supply of omega-3 fatty acids, from foods such as fish and oily fish and/or from supplements providing DHA and EPA, or DHA alone, with a regular intake of at least 250 mg/day. For pregnant women, there is, in general, a need for an additional intake of 100–200 mg/day.

In pregnant women with low DHA intake and/or low DHA blood levels, because they are at increased risk of PTB and early PTB, they should receive an additional supply of about 600–1000 mg/day, starting from 20 weeks and continuing until about 37 weeks of gestation.

It is therefore a goal to identify these women at increased risk of PTB due to low DHA intake and/or low DHA levels, and this is achievable by screening with a few questions on dietary intake of foods rich in DHA and EPA and on use of omega-3 supplements or with a DHA measurement from a blood lipid component, although this needs further standardization. This information should be provided to all women of childbearing age, as well as to pregnant women and their partners.

After pregnancy, a balanced diet with adequate fat intake is also important, aiming for 20–35% of daily calories to be from fat, similar to non-pregnant women, while focusing on healthy fats and limiting saturated and trans fats. In this period, women should follow a healthy diet and, in addition to limiting saturated fats, they should increase their intake of foods containing antioxidants.

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