Fish and pregnancy: which ones can you eat?

Fish contains a significant amount of omega-3s, including DHA and EPA. These fatty acids are very important for health, as numerous studies show they help reduce mortality and the incidence of cardiovascular disease, particularly when they come from fish. They have, among other things, an anti-inflammatory effect and an impact on immunity [1]. 

Regarding heart health, research has shown that EPA and DHA contribute to normalising plasma lipid levels (i.e. reducing triglycerides), and to reducing blood pressure and the tendency towards thrombosis [1]. 

DHA is also a physiologically essential nutrient in the brain for the normal functioning of neural tissue (particularly for cognitive performance, learning ability, memory, etc.), and in the retina of the eye for visual acuity [1]. Furthermore, EPA consumption may potentially reduce the risk of pre-eclampsia and influence the timing of delivery [2].

After birth, omega-3 deficits can persist for up to six weeks following delivery, particularly in breastfeeding mothers [3]. Several studies have demonstrated a link between low omega-3 intake in the mother and depressive symptoms in the postpartum period [4]. Changes in the long-chain polyunsaturated fatty acid status of the brain, in particular a reduction in DHA, are associated with postnatal depression [5].
Furthermore, an imbalance between omega-6 and omega-3 in early pregnancy increases the risk of postnatal depression during the year following birth [6]. Fish consumption levels, and EPA and DHA intake, may be inversely associated with depressive symptoms during pregnancy [7].

The milk content of omega-3 DHA is solely dependent on maternal dietary intake. It can be synthesised in the body from alpha-linolenic acid (ALA), which is found mainly in oils (linseed, walnut, rapeseed and soya) and in seeds (flax, chia, walnut). However, as this synthesis is very limited in the foetus and placenta, the mother's nutritional status and placental function are essential for its supply to the foetus.

Maternal diet can have a significant impact on the qualitative profile of milk lipids, including DHA content [8], which makes it all the more important to pay close attention to our omega-3 and DHA intake during these periods — both for ourselves and our child.

Maternal and foetal thyroid hormones regulate key processes in the development of the foetal brain and nervous system, including nerve cell growth and neuron formation [11]. Nervous tissue begins to develop at 2 months of pregnancy. A low intake during this period can slow children's physical growth and have detrimental effects on mental development.

Iodine is also one of the rare minerals, along with selenium, where the level in breast milk is entirely dependent on the mother's status — hence the importance of adequate iodine intake for the breastfeeding mother, both for her own health and that of her baby. If needed, you can take a post-partum supplement per container. 

Dietary intake of fatty acids from fish, particularly long-chain polyunsaturated fatty acids such as DHA and EPA, is important during pregnancy to meet the needs of the developing foetus. The baby's brain is composed of 60% lipids, notably DHA, which may influence the development of the foetal brain and retina [11]. This intake is particularly important during the third trimester due to the rapid development of the foetal brain. Furthermore, other studies have shown that consuming one or more portions of fish per week during pregnancy had a positive effect on the child's cognitive development [12].

Consuming more than two portions of fish per day during pregnancy has also been shown to have a protective effect against attention disorders (impulsivity and hyperactivity) in children aged 8, according to data gathered from the New Bedford birth cohort [13].

The association between fish consumption during pregnancy and birth outcomes has been studied. One study found that women who eat fish more than once a week have a lower risk of premature birth than women who eat fish less than once a week. The potential benefit of fish consumption on the risk of premature birth may be attributed to their omega-3 content [14]. 

A prospective study, the subject of two publications, found an increased risk of premature birth in women who do not consume fish during pregnancy [15].
ANSES considers the relationship between fish consumption and a reduced risk of premature birth to be probable.

ANSES also suggests that, based on certain studies, eating fish during pregnancy may reduce the risk of eczema in the child. 

These are the fish most likely to contain the highest levels of methylmercury. Because these fish are at the top of the food chain, they accumulate the mercury found in their environment as well as that present in the smaller fish they consume.