Salmon In Pregnancy Study (SIPS): the effects of increased oily fish intake during pregnancy on maternal and cord blood fatty acid composition, cord blood immunity and atopy outcomes in infants at 6 months of age

Abstract

Parallel increases in many inflammatory diseases including atopy over the last 40 years suggest that common environmental changes may be promoting inflammatory immune responses. Modern diets have become increasingly rich in n-6 polyunsaturated fatty acids (PUFAs) and relatively deficient in n-3 PUFAs. These dietary changes are believed to promote a pro-sensitisation, pro-allergic and pro-inflammatory environment. Exposure to such an environment during pregnancy and in the very early life period is considered to influence subsequent patterns of the immature and developing neonatal immune system, and this may contribute to the increase in allergic disease in early life. As allergic diseases often first manifest in infancy, prevention strategies need to be targeted early, even in utero. Epidemiologic and experimental data provide a plausible link between dietary changes and increased incidence of childhood atopic disease. Although there have been studies examining the potential benefits of giving n-3 PUFA-rich fish oil supplements during pregnancy, there are no studies examining the effects of increased consumption of oily fish in pregnancy on neonatal immune responses and subsequent clinical outcomes.

The Salmon in Pregnancy Study (SIPS) is the first randomised controlled trial of oily fish intervention during pregnancy. The hypotheses being investigated in SIPS is that increased intake of salmon, a source of long chain (LC) n-3 PUFAs (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)), in pregnancy will a) increase maternal LC n-3 PUFA intake, b) increase maternal and infant blood LC n-3 PUFA status, c) modulate fetal/neonatal immune responses and d) lower the risk of infant atopy determined at 6 months of age. The primary outcome measures of SIPS were the clinical signs of atopy in the offspring.

Pregnant women (n=123) at high risk of having atopic offspring, and with low habitual intake of oily fish (? 2/month) were randomised at 20 weeks of pregnancy to either consuming 2 portions/week of farmed salmon (n=62) or continuing their habitual diet (n=61) until the end of pregnancy. The woman attended a clinic at 20 (n=123), 34 (n=110) and 38 (n=91) weeks of gestation at which fasting blood was collected and a food frequency questionnaire (FFQ) was administered (at 20 and 34 weeks). At delivery umbilical cord blood was collected (n=101) for fatty acid and immunological analysis. Infants attended a clinic at 6 months of age (n=86) for assessment of allergic sensitisation by skin prick testing (SPT) using various allergen extracts and of atopic dermatitis (SCORAD index).

Maternal and cord plasma and cord blood mononuclear cell (CBMC) fatty acid compositions were determined by gas chromatography. Neonatal (cord) immune cell subsets were identified by flow cytometry. Ex-vivo cytokine production by CBMC in response to stimulants (allergen, mitogen, and toll-like receptor (TLR) ligands) was determined by cytometric bead array and flow cytometry. Ex-vivo prostaglandin E2 production by CBMC was determined by enzyme-linked immunosorbent assay. Immunoglobin E concentration was measured in cord blood plasma and in 6 month infant blood plasma.

Eating oily fish twice a week during pregnancy resulted in a higher maternal intake of LC n-3 PUFAs (both EPA and DHA) and in higher maternal and cord blood plasma status of LC n-3 PUFAs (both EPA and DHA). LC n-3 PUFA content of CBMC was not significantly affected. CBMC production of interleukins-2, -4, -5, and -10 and tumour necrosis factor-? was lower in the salmon group. There was no effect of salmon on the atopic outcomes assessed at 6 months.

More information

Identifiers

ORCID for P.C. Calder: orcid.org/0000-0002-6038-710X

Catalogue record

Export record