General obstetrics: Fish oil in various doses or flax oil in pregnancy and timing of spontaneous delivery: a randomised controlled trial

Omega-3 fatty acid addition during pregnancy

BACKGROUND

Higher intakes of foods containing omega-3 long-chain polyunsaturated fatty acids (LCPUFA), such as fish, during pregnancy have been associated with longer gestations and improved perinatal outcomes. This is an update of a review that was first published in 2006.

OBJECTIVES

To assess the effects of omega-3 LCPUFA, as supplements or as dietary additions, during pregnancy on maternal, perinatal, and neonatal outcomes and longer-term outcomes for mother and child.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (16 August 2018), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing omega-3 fatty acids (as supplements or as foods, stand-alone interventions, or with a co-intervention) during pregnancy with placebo or no omega-3, and studies or study arms directly comparing omega-3 LCPUFA doses or types. Trials published in abstract form were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data, assessed risk of bias in trials and assessed quality of evidence for prespecified birth/infant, maternal, child/adult and health service outcomes using the GRADE approach.

MAIN RESULTS

In this update, we included 70 RCTs (involving 19,927 women at low, mixed or high risk of poor pregnancy outcomes) which compared omega-3 LCPUFA interventions (supplements and food) compared with placebo or no omega-3. Overall study-level risk of bias was mixed, with selection and performance bias mostly at low risk, but there was high risk of attrition bias in some trials. Most trials were conducted in upper-middle or high-income countries; and nearly half the trials included women at increased/high risk for factors which might increase the risk of adverse maternal and birth outcomes.Preterm birth < 37 weeks (13.4% versus 11.9%; risk ratio (RR) 0.89, 95% confidence interval (CI) 0.81 to 0.97; 26 RCTs, 10,304 participants; high-quality evidence) and early preterm birth < 34 weeks (4.6% versus 2.7%; RR 0.58, 95% CI 0.44 to 0.77; 9 RCTs, 5204 participants; high-quality evidence) were both lower in women who received omega-3 LCPUFA compared with no omega-3. Prolonged gestation > 42 weeks was probably increased from 1.6% to 2.6% in women who received omega-3 LCPUFA compared with no omega-3 (RR 1.61 95% CI 1.11 to 2.33; 5141 participants; 6 RCTs; moderate-quality evidence).For infants, there was a possibly reduced risk of perinatal death (RR 0.75, 95% CI 0.54 to 1.03; 10 RCTs, 7416 participants; moderate-quality evidence: 62/3715 versus 83/3701 infants) and possibly fewer neonatal care admissions (RR 0.92, 95% CI 0.83 to 1.03; 9 RCTs, 6920 participants; moderate-quality evidence - 483/3475 infants versus 519/3445 infants). There was a reduced risk of low birthweight (LBW) babies (15.6% versus 14%; RR 0.90, 95% CI 0.82 to 0.99; 15 trials, 8449 participants; high-quality evidence); but a possible small increase in large-for-gestational age (LGA) babies (RR 1.15, 95% CI 0.97 to 1.36; 6 RCTs, 3722 participants; moderate-quality evidence, for omega-3 LCPUFA compared with no omega-3. Little or no difference in small-for-gestational age or intrauterine growth restriction (RR 1.01, 95% CI 0.90 to 1.13; 8 RCTs, 6907 participants; moderate-quality evidence) was seen.For the maternal outcomes, there is insufficient evidence to determine the effects of omega-3 on induction post-term (average RR 0.82, 95% CI 0.22 to 2.98; 3 trials, 2900 participants; low-quality evidence), maternal serious adverse events (RR 1.04, 95% CI 0.40 to 2.72; 2 trials, 2690 participants; low-quality evidence), maternal admission to intensive care (RR 0.56, 95% CI 0.12 to 2.63; 2 trials, 2458 participants; low-quality evidence), or postnatal depression (average RR 0.99, 95% CI 0.56 to 1.77; 2 trials, 2431 participants; low-quality evidence). Mean gestational length was greater in women who received omega-3 LCPUFA (mean difference (MD) 1.67 days, 95% CI 0.95 to 2.39; 41 trials, 12,517 participants; moderate-quality evidence), and pre-eclampsia may possibly be reduced with omega-3 LCPUFA (RR 0.84, 95% CI 0.69 to 1.01; 20 trials, 8306 participants; low-quality evidence).For the child/adult outcomes, very few differences between antenatal omega-3 LCPUFA supplementation and no omega-3 were observed in cognition, IQ, vision, other neurodevelopment and growth outcomes, language and behaviour (mostly low-quality to very low-quality evidence). The effect of omega-3 LCPUFA on body mass index at 19 years (MD 0, 95% CI -0.83 to 0.83; 1 trial, 243 participants; very low-quality evidence) was uncertain. No data were reported for development of diabetes in the children of study participants.

AUTHORS' CONCLUSIONS

In the overall analysis, preterm birth < 37 weeks and early preterm birth < 34 weeks were reduced in women receiving omega-3 LCPUFA compared with no omega-3. There was a possibly reduced risk of perinatal death and of neonatal care admission, a reduced risk of LBW babies; and possibly a small increased risk of LGA babies with omega-3 LCPUFA.For our GRADE quality assessments, we assessed most of the important perinatal outcomes as high-quality (e.g. preterm birth) or moderate-quality evidence (e.g. perinatal death). For the other outcome domains (maternal, child/adult and health service outcomes) GRADE ratings ranged from moderate to very low, with over half rated as low. Reasons for downgrading across the domain were mostly due to design limitations and imprecision.Omega-3 LCPUFA supplementation during pregnancy is an effective strategy for reducing the incidence of preterm birth, although it probably increases the incidence of post-term pregnancies. More studies comparing omega-3 LCPUFA and placebo (to establish causality in relation to preterm birth) are not needed at this stage. A further 23 ongoing trials are still to report on over 5000 women, so no more RCTs are needed that compare omega-3 LCPUFA against placebo or no intervention. However, further follow-up of completed trials is needed to assess longer-term outcomes for mother and child, to improve understanding of metabolic, growth and neurodevelopment pathways in particular, and to establish if, and how, outcomes vary by different types of omega-3 LCPUFA, timing and doses; or by characteristics of women.

Adaptive thermogenesis by dietary n-3 polyunsaturated fatty acids: Emerging evidence and mechanisms

Brown/beige fat plays a crucial role in maintaining energy homeostasis through non-shivering thermogenesis in response to cold temperature and excess nutrition (adaptive thermogenesis). Although numerous molecular and genetic regulators have been identified, relatively little information is available regarding thermogenic dietary molecules. Recently, a growing body of evidence suggests that high consumption of n-3 polyunsaturated fatty acids (PUFA) or activation of GPR120, a membrane receptor of n-3 PUFA, stimulate adaptive thermogenesis. In this review, we summarize the emerging evidence that n-3 PUFA promote brown/beige fat formation and highlight the potential mechanisms whereby n-3 PUFA require GPR120 as a signaling platform or act independently. Human clinical trials are revisited in the context of energy expenditure. Additionally, we explore some future perspective that n-3 PUFA intake might be a useful strategy to boost or sustain metabolic activities of brown/beige fat at different lifecycle stages of pregnancy and senescence. Given that a high ratio of n-6/n-3 PUFA intake is associated with the development of obesity and type 2 diabetes, understanding the impact of n-6/n-3 ratio on energy expenditure and adaptive thermogenesis will inform the implementation of a novel nutritional strategy for preventing obesity.

Herbal Therapy in Pregnancy-What to Expect when you Expect?

The use of herbal therapy in pregnancy is common for pregnancy related nausea, vomiting, gestational diabetes, anxiety, insomnia, and preparation for labor, as well as for treating infections. Many conventional drugs may interfere with fetal development and herbal products are considered to be safe. However, herbal therapy requires competent healthcare professional advice before prescribing. Knowledge about the possible adverse effects of active compounds of the herbs on pregnancy outcome is limited. Interference of herbal ingredients with conventional medication or the ailment should also not be excluded. For many herbal products, the pharmacological effect is not clinically proven, and the safe usage in pregnancy is not guaranteed. Here, based on published clinical trials, an overview is given of the efficacy and safety for fetal development and pregnancy outcome of the most frequently used herbs: ginger, cranberry, echinacea, mint, chamomile, valerian, flaxseed, tea and raspberry leaf.

Maternal intake of seafood and supplementary long chain n-3 poly-unsaturated fatty acids and preterm delivery

BACKGROUND

Preterm delivery increases the risk of neonatal morbidity and mortality. Studies suggest that maternal diet may affect the prevalence of preterm delivery. The aim of this study was to assess whether maternal intakes of seafood and marine long chain n-3 polyunsaturated fatty acids (LCn-3PUFA) from supplements were associated with preterm delivery.

METHODS

The study population included 67,007 women from the Norwegian Mother and Child Cohort Study. Maternal food and supplement intakes were assessed by a validated self-reported food frequency questionnaire in mid-pregnancy. Information about gestational duration was obtained from the Medical Birth Registry of Norway. We used Cox regression to estimate hazard ratios (HR) with 95% confidence intervals (CI) for associations between total seafood, lean fish, fatty fish, and LCn-3PUFA intakes and preterm delivery. Preterm was defined as any onset of delivery before gestational week 37, and as spontaneous or iatrogenic deliveries and as preterm delivery at early, moderate, and late preterm gestations.

RESULTS

Lean fish constituted 56%, fatty fish 34% and shellfish 10% of seafood intake. Any intake of seafood above no/rare intake (>5 g/d) was associated with lower prevalence of preterm delivery. Adjusted HRs were 0.76 (CI: 0.66, 0.88) for 1-2 servings/week (20-40 g/d), 0.72 (CI: 0.62, 0.83) for 2-3 servings/week (40-60 g/d), and 0.72 (CI: 0.61, 0.85) for ≥3 servings/week (>60 g/d), p-trend <0.001. The association was seen for lean fish (p-trend: 0.005) but not for fatty fish (p-trend: 0.411). The intake of supplementary LCn-3PUFA was associated only with lower prevalence of early preterm delivery (before 32 gestational weeks), while increasing intake of LCn-3PUFA from food was associated with lower prevalence of overall preterm delivery (p-trend: 0.002). Any seafood intake above no/rare was associated with lower prevalence of both spontaneous and iatrogenic preterm delivery, and with lower prevalence of late preterm delivery.

CONCLUSIONS

Any intake of seafood above no/rare consumption was associated with lower prevalence of preterm delivery. The association was stronger for lean than for fatty fish. Intake of supplementary LCn-3PUFA was associated only with early preterm delivery. The findings corroborate the current advice to include fish and seafood as part of a balanced diet during pregnancy.

Omega-3 supplementation during pregnancy to prevent recurrent intrauterine growth restriction: systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

To evaluate the efficacy of omega-3 supplementation during pregnancy in preventing intrauterine growth restriction (IUGR) in women with apparently uncomplicated singleton pregnancy and previous IUGR pregnancy.

METHODS

For this systematic review, the research protocol was designed a priori. Searches were performed in electronic databases for studies published from inception of each database to December 2014. A combination of search terms was used including 'fish oil', 'long chain polyunsaturated fatty acids', 'intrauterine growth restriction', 'small for gestational age' and 'omega-3'. We included all randomized controlled trials (RCTs) of women with an uncomplicated singleton pregnancy and a prior IUGR pregnancy who were randomized to receive prophylactic treatment with omega-3 supplementation or either placebo or no treatment (control). Trials that included women with multiple gestations and those with only biochemical outcomes available were excluded. Pooled estimates were based on relative risk (RR) with 95% CI. Primary outcome was incidence of IUGR as defined in the RCTs.

RESULTS

Three RCTs including 575 women with uncomplicated singleton pregnancy with prior IUGR were analyzed. Women who received omega-3 supplementation during pregnancy had the same incidence of IUGR, defined as estimated fetal weight < 5(th) or < 3(rd) centiles, as had controls (22.8% vs 20.2%, respectively; RR, 1.13 (95% CI, 0.83-1.54)). Compared to controls, women who received omega-3 supplementation delivered later (mean difference, 1.4 (95% CI, 1.28-1.63) weeks), had a longer latency (mean difference, 2 (95% CI, 1.73-2.08) weeks), had a similar incidence of perinatal death (2.1% vs 3.3%, respectively; RR, 0.60 (95% CI, 0.15-2.42)) and similar birth weight (mean difference, 50 g (95% CI, -26 to 246 g)).

CONCLUSIONS

Omega-3 supplementation during pregnancy does not prevent recurrence of IUGR in women with uncomplicated singleton pregnancy and a previous IUGR pregnancy.

Omega-3 long-chain polyunsaturated fatty acids and fish oil supplementation during pregnancy: which evidence?

OBJECTIVE

The aim of this study was to provide evidence-based recommendations for omega-3 supplementation during pregnancy through a systematic review of level-1 data published on this topic.

METHODS

We reviewed all randomized-controlled trials (RCTs) including women who were randomized to treatment with either omega-3 supplementation or control (placebo or no treatment) during pregnancy and analyzed all the outcomes reported in the trials, separately. We planned to evaluate the effect of omega-3 on: preterm birth (PTB); pre-eclampsia (PE) and intrauterine growth restriction (IUGR); gestational diabetes; perinatal mortality; small for gestational age (SGA) and birth weight; infant eye and brain development; and postpartum depression.

RESULTS

We identified 34 RCTs including 14 106 singletons and 2578 twins. These level-1 data showed that omega-3 was not associated with prevention of PTB, PE, IUGR, gestational diabetes, SGA, post-partum depression or better children development. Data about birth weight, perinatal mortality and childhood cognitive outcome were limited. Women with gestational diabetes who received omega-3 had significantly lower serum C-reactive protein concentrations, low incidence of hyperbilirubinemia in newborns and decreased newborns' hospitalization rate.

CONCLUSIONS

There was not enough evidence to support the routine use of omega-3 supplementation during pregnancy. Given the 73% significant decrease in perinatal death in the singleton gestations who started omega-3 supplementation ≤ 20 weeks, further research is needed. Large RCTs in multiple gestations and longer follow-up are also required.

The Effect of Omega-3 Docosahexaenoic Acid Supplementation on Gestational Length: Randomized Trial of Supplementation Compared to Nutrition Education for Increasing n-3 Intake from Foods

OBJECTIVE

DHA supplementation was compared to nutrition education to increase DHA consumption from fish and DHA fortified foods.

DESIGN

This two-part intervention included a randomized double-blind placebo controlled DHA supplementation arm and a nutrition education arm designed to increase intake of DHA from dietary sources by 300 mg per day.

SETTING

Denver Health Hospitals and Clinics, Denver, Colorado, USA.

POPULATION

871 pregnant women aged 18-40 were recruited between 16 and 20 weeks of gestation of whom 564 completed the study and complete delivery data was available in 505 women and infants.

METHODS

Subjects received either 300 or 600 mg DHA or olive oil placebo or nutrition education.

MAIN OUTCOME VARIABLE

Gestational length.

RESULTS

Gestational length was significantly increased by 4.0-4.5 days in women supplemented with 600 mg DHA per day or provided with nutrition education. Each 1% increase in RBC DHA at delivery was associated with a 1.6-day increase in gestational length. No significant effects on birth weight, birth length, or head circumference were demonstrated. The rate of early preterm birth (1.7%) in those supplemented with DHA (combined 300 and 600 mg/day) was significantly lower than in controls.

CONCLUSION

Nutrition education or supplementation with DHA can be effective in increasing gestational length.

Omega-3 supplementation to prevent recurrent preterm birth: a systematic review and metaanalysis of randomized controlled trials

The purpose of this study was to evaluate the efficacy of omega-3 supplementation for the prevention of recurrent preterm birth (PTB) in asymptomatic singleton gestations with previous PTB. We searched fish oil, long chain polyunsaturated fatty acids, pregnancy, and omega-3 in MEDLINE, OVID, Scopus, ClinicalTrials.gov, the PROSPERO International Prospective Register of Systematic Reviews, EMBASE, and the Cochrane Central Register of Controlled Trials from inception of each database to December 2014 with no limit for language. In addition the reference lists of all identified articles were examined to identify studies that were not captured by electronic searches. We performed a metaanalysis of randomized controlled trials of asymptomatic singleton gestations with previous PTB who were assigned randomly to prophylactic omega-3 supplementation vs control (either placebo or no treatment). The primary outcome was predefined as PTB at <37 weeks of gestation. The pooled results were reported as relative risk (RR) with 95% confidence interval (95% CI). The protocol of this review was registered with PROSPERO (registration number: CRD42015016371). Two randomized controlled trials that included 1080 women were analyzed. The mean gestational age at randomization was approximately 134 days in both groups (mean difference, 0.01 days; 95% CI, -0.13 to 0.14). Women who received omega-3 had similar rates of PTB at <37 weeks of gestation (34.5% vs 39.8%; RR, 0.81; 95% CI, 0.59-1.12) and PTB at <34 weeks of gestation (12.0% vs 15.4%; RR, 0.62; 95% CI, 0.26-1.46) compared with control subjects. The omega-3 groups had a statistically significantly longer latency (mean difference, 2.10 days; 95% CI, 1.98-2.22) and higher birthweight (mean difference, 102.52 g; 95% CI, 20.09-184.95) compared with control subjects; the other secondary outcomes (which included gestational age at delivery, spontaneous PTB at <37 and 34 weeks of gestation, admission to the intensive care unit, intraventricular hemorrhage, necrotizing enterocolitis, sepsis, and perinatal death) were similar. Omega-3 supplementation during pregnancy does not prevent recurrent PTB in asymptomatic singleton gestations with previous PTB. The benefits in longer latency and higher birth weight may deserve further study.

Maternal prenatal and/or postnatal n-3 long chain polyunsaturated fatty acids (LCPUFA) supplementation for preventing allergies in early childhood

BACKGROUND

Allergies have become more prevalent globally over the last 20 years. Dietary consumption of n-3 (or omega 3) long chain polyunsaturated fatty acids (LCPUFA) has declined over the same period of time. This, together with the known role of n-3 LCPUFA in inhibiting inflammation, has resulted in speculation that n-3 LCPUFA may prevent allergy development. Dietary n-3 fatty acids supplements may change the developing immune system of the newborn before allergic responses are established, particularly for those with a genetic predisposition to the production of the immunoglobulin E (IgE) antibody. Individuals with IgE-mediated allergies have both the signs and symptoms of the allergic disease and a positive skin prick test (SPT) to the allergen.

OBJECTIVES

To assess the effect of n-3 LCPUFA supplementation in pregnant and/or breastfeeding women on allergy outcomes (food allergy, atopic dermatitis (eczema), allergic rhinitis (hay fever) and asthma/wheeze) in their children.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (6 August 2014), PubMed (1966 to 01 August 2014), CINAHL via EBSCOhost (1984 to 01 August 2014), Scopus (1995 to 01 August 2014), Web of Knowledge (1864 to 01 August 2014) and ClinicalTrials.gov (01 August 2014) and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) evaluating the effect of n-3 LCPUFA supplementation of pregnant and/or lactating women (compared with placebo or no treatment) on allergy outcomes of the infants or children. Trials using a cross-over design and trials examining biochemical outcomes only were not eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed eligibility and trial quality and performed data extraction. Where the review authors were also investigators on trials selected, an independent reviewer assessed trial quality and performed data extraction.

MAIN RESULTS

Eight trials involving 3366 women and their 3175 children were included in the review. In these trials, women were supplemented with n-3 LCPUFA during pregnancy (five trials), lactation (two trials) or both pregnancy and lactation (one trial). All trials randomly allocated women to either a n-3 LCPUFA supplement or a control group. The risk of bias varied across the eight included trials in this review with only two trials with a low risk of selection, performance and attrition bias.N-3 LCPUFA supplementation showed a clear reduction in the primary outcome of any allergy (medically diagnosed IgE mediated) in children aged 12 to 36 months (risk ratio (RR) 0.66, 95% confidence interval (CI) 0.44 to 0.98; two RCTs; 823 children), but not beyond 36 months (RR 0.86, 95% CI 0.61 to 1.20; one RCT, 706 children). For any allergy (medically diagnosed IgE mediated and/or parental report), no clear differences were seen in children either at 12 to 36 months (RR 0.89, 95% CI 0.71 to 1.11; two RCTs, 823 children) or beyond 36 months of age (RR 0.96, 95% CI 0.84 to 1.09; three RCTs, 1765 children).For the secondary outcomes of specific allergies there were no clear differences for food allergies at 12 to 36 months and beyond 36 months, but a clear reduction was seen for children in their first 12 months with n-3 LCPUFA (both for medically diagnosed IgE mediated and medically diagnosed IgE mediated and/or parental report). There was a clear reduction in medically diagnosed IgE-mediated eczema with n-3 LCPUFA for children 12 to 36 months of age, but not at any other time point for both medically diagnosed IgE mediated and medically diagnosed IgE mediated and/or parental report. No clear differences for allergic rhinitis or asthma/wheeze were seen at any time point for both medically diagnosed IgE mediated, and medically diagnosed IgE mediated and/or parental report.There was a clear reduction in children's sensitisation to egg and sensitisation to any allergen between 12 to 36 months of age when mothers were supplemented with n-3 LCPUFA.In terms of safety for the mother and child, n-3 LCPUFA supplementation during pregnancy did not show increased risk of postpartum haemorrhage or early childhood infections.

AUTHORS' CONCLUSIONS

Overall, there is limited evidence to support maternal n-3 LCPUFA supplementation during pregnancy and/or lactation for reducing allergic disease in children. Few differences in childhood allergic disease were seen between women who were supplemented with n-3 LCPUFA and those who were not.

Omega-3 long chain polyunsaturated fatty acids to prevent preterm birth: a systematic review and meta-analysis

OBJECTIVE

To evaluate the efficacy of omega-3 in reducing the incidence of preterm birth.

DATA SOURCES

Searches were performed in MEDLINE, OVID, Scopus, ClinicalTrials.gov, the PROSPERO International Prospective Register of Systematic Reviews, EMBASE, and the Cochrane Central Register of Controlled Trials with the use of a combination of keywords related to "fish oil," "pregnancy," and "omega-3."

METHODS OF STUDY SELECTION

We included all randomized controlled trials of asymptomatic women with singleton gestations who were randomized to prophylactic treatment with either omega-3 supplementation or control (either placebo or no treatment). Exclusion criteria included trials in women with multiple gestations, intrauterine growth restriction, gestational hypertension or preeclampsia at randomization, prior preterm birth, and trials with polyunsaturated fatty acids as control.

TABULATION, INTEGRATION, AND RESULTS

Nine randomized trials including 3,854 eligible women were identified. Women who received omega-3 had a similar rate of preterm birth before 37 weeks of gestation compared with women in the control group (7.7% compared with 9.1%, respectively; relative risk 0.90, 95% confidence interval [CI] 0.72-1.11). There were no significant differences in birth weight, neonatal intensive care unit admission, necrotizing enterocolitis, sepsis, or perinatal death in the omega-3 compared with control groups, respectively. There were no significant differences in the subgroup analyses, except for the rate of perinatal death, which was lower (0.3% compared with 1.2%; relative risk 0.27, 95% CI 0.09-0.80) in the women who received omega-3 before 21 weeks of gestation and in trials with low risk of bias (0.3% compared with 1.0%; relative risk 0.28, 95% CI 0.09-0.89) compared with women in the control group. However, in no randomized controlled trial was perinatal death the primary outcome.

CONCLUSION

Omega-3 supplementation during pregnancy does not reduce the incidence of preterm birth or improve neonatal outcome.

Effect of n-3 long-chain polyunsaturated fatty acid intake during pregnancy on maternal, infant, and child health outcomes: a systematic review

Evidence from observational studies and randomised trials has suggested a potential association between intake of n-3 long-chain polyunsaturated fatty acids (LCPUFA) during pregnancy and certain pregnancy and birth outcomes. Marine foods (e.g. fatty sea fish, algae) and select freshwater fish contain pre-formed n-3 LCPUFA, which serve as precursors for bioactive molecules (e.g. prostaglandins) that influence a variety of biological processes. The main objective of this analysis was to summarise evidence of the effect of n-3 LCPUFA intake during pregnancy on select maternal and child health outcomes. Searches were performed in PubMed, EMBASE, and other electronic databases to identify trials where n-3 LCPUFA were provided to pregnant women for at least one trimester of pregnancy. Data were extracted into a standardised abstraction table and pooled analyses were conducted using RevMan software. Fifteen randomised controlled trials were eligible for inclusion in the meta-analysis, and 14 observational studies were included in the general review. n-3 LCPUFA supplementation during pregnancy resulted in a modest increase in birthweight (mean difference = 42.2 g; [95% CI 14.8, 69.7]) and no significant differences in birth length or head circumference. Women receiving n-3 LCPUFA had a 26% lower risk of early preterm delivery (<34 weeks) (RR = 0.74; [95% CI 0.58, 0.94]) and there was a suggestion of decreased risk of preterm delivery (RR = 0.91; [95% CI 0.82, 1.01]) and low birthweight (RR = 0.92; [95% CI 0.83, 1.02]). n-3 LCPUFA in pregnancy did not influence the occurrence of pre-eclampsia, high blood pressure, infant death, or stillbirth. Our review of observational studies revealed mixed findings, with several large studies reporting positive associations between fish intake and birthweight and several reporting no associations. In conclusion, n-3 LCPUFA supplementation during pregnancy resulted in a decreased risk of early preterm delivery and a modest increase in birthweight. More studies in low- and middle-income countries are needed to determine any effect of n-3 LCPUFA supplementation in resource-poor settings, where n-3 PUFA intake is likely low.

Omega 3 fatty acids, gestation and pregnancy outcomes

Pregnancy is associated with a reduction in maternal serum docosahexaenoic acid (DHA, 22:6 n-3) percentage and its possible depletion in the maternal store. Since the synthesis of long chain polyunsaturated fatty acids (LCPUFA) in the fetus and placenta is low, both the maternal LCPUFA status and placental function are critical for their supply to the fetus. Maternal supplementation with DHA up to 1 g/d or 2·7 g n-3 LCPUFA did not have any harmful effect. DHA supplementation in large studies slightly the enhanced length of gestation (by about 2 days), which may increase the birth weight by about 50 g at delivery. However no advice can be given on their general using to avoid preterm deliveries in low or high risk pregnancies. Several studies, but not all, reported improvements of the offspring in some neurodevelopmental tests as a result of DHA supplementation during gestation, or, at least, positive relationships between maternal or cord serum DHA percentages and cognitive skills in young children. The effect seems more evident in children with low DHA proportions, which raises the question of how to identify those mothers who might have a poor DHA status and who could benefit from such supplementation. Most studies on the effects of n-3 LCPUFA supplementation during pregnancy on maternal depression were judged to be of low-to-moderate quality, mainly due to small sample sizes and failure to adhere to Consolidated Standards of Reporting Trials guidelines. In contrast, the effects of n-3 LCPUFA supplementation on reducing allergic diseases in offspring are promising.

An audit of seafood consumption awareness during pregnancy and its association with maternal and fetal outcomes in a Turkish population

This study was conducted to audit maternal seafood intake awareness during pregnancy and to determine whether there is an association between fish consumption and various pregnancy outcomes. In total, 553 low-risk and healthy pregnant women were given a questionnaire concerning fish consumption. Pregnant women who developed gestational diabetes mellitus, pre-term labour-birth, macrosomia, low birth weight and small for gestational age were analysed. Fatty fish consumers tended to have higher birth weight infants than lean fish consumers. Low fish consumption was significantly correlated with low birth weight and small for gestational age (SGA) infants. The more fatty fish that the low fish consumers consumed, the more likely they were to have SGA infants. Fish consumption did not have an impact on the development of gestational diabetes mellitus, macrosomia or pre-term labour-birth. Low fish consumption during pregnancy may be associated with the development of low birth weight and SGA infants in a Turkish population.

Association between maternal seafood consumption before pregnancy and fetal growth: evidence for an association in overweight women. The EDEN mother-child cohort

Studies in countries with high seafood consumption have shown a benefit on fetal growth and child development. The objective of our study was to determine the association between seafood consumption in French pregnant women and fetal growth. Pregnant women included in the EDEN mother-child cohort study completed two food frequency questionnaires on their usual diet in the year before and during the last 3 months of pregnancy (n = 1805). Fetal circumferences were measured by ultrasound and anthropometry at birth. Variables were compared across tertiles of the mother's seafood consumption using multiple linear regression to adjust for confounding variables. Analyses were stratified by maternal overweight status because of an interaction between maternal seafood consumption and her body mass index (P < 0.01). There was no association between seafood intake and fetal growth in the whole sample of women. For overweight women (n = 464), higher consumption of seafood before pregnancy was associated with higher fetal biparietal and abdominal circumferences and anthropometric measures. From the lowest to the highest tertiles, mean birthweight was 167 g higher (P = 0.002). No significant association was found with consumption at the end of pregnancy. In conclusion, high seafood consumption before pregnancy is positively associated with fetal growth in overweight women.

Maternal fish and shellfish intake and pregnancy outcomes: a prospective cohort study in Brittany, France

BACKGROUND

Recommendations about risks and benefits of seafood intake during pregnancy have been published in the last decade, but the specific health effects of the different categories of seafood remain unknown. Fish and shellfish may differ according to their fatty acid content and their concentration of chemical pollutants and toxins. Not taking these particularities into account may result in underestimating of both the positive and negative effects of seafood on birth outcomes and partly explains inconsistent results on the subject.

METHODS

In the PELAGIE cohort study, including 2398 pregnant women from Brittany, we fit multiple linear and logistic regression models to examine associations of fish (salt-water fish only) and shellfish intake before pregnancy with length of gestation, birthweight, and risks of preterm births, low birthweight or small-for-gestational-age (SGA) babies.

RESULTS

When fish and shellfish consumptions were considered simultaneously, we observed a decrease in the risk of SGA birth with increasing frequency of fish intake: OR = 0.57 (95%CI: 0.31 to 1.05) for women eating fish twice a week or more compared with those eating it less than once a month. The risk of SGA birth was significantly higher among women eating shellfish twice a week or more than among those eating it less than once a month: OR = 2.14 (95%CI: 1.13 to 4.07). Each additional monthly meal including fish was significantly related to an increase in gestational length of 0.02 week (95%CI: 0.002 to 0.035). No association was observed with birthweight or preterm birth.

CONCLUSION

These results suggest that different categories of seafood may be differently associated with birth outcomes, fish consumption with increased length of gestation and shellfish consumption with decreased fetal growth.

Placental transfer of long-chain polyunsaturated fatty acids (LC-PUFA)

Considerable evidence exists for marked beneficial effects of omega-3 long-chain polyunsaturated fatty acids (LC-PUFA) during pregnancy. The omega-3 LC-PUFA docosahexaenoic acid (DHA) is incorporated in large amounts in fetal brain and other tissues during the second half of pregnancy, and several studies have provided evidence for a link between early DHA status of the mother and visual and cognitive development of her child after birth. Moreover, the supplementation of omega-3 LC-PUFA during pregnancy increases slightly infant size at birth, and significantly reduces early preterm birth before 34 weeks of gestation by 31%. In our studies using stable isotope methodology in vivo, we demonstrated active and preferential materno-fetal transfer of DHA across the human placenta and found the expression of human placental fatty acid binding and transport proteins. From the correlation of DHA values with placental fatty acid transport protein 4 (FATP 4), we conclude that this protein is of key importance in mediating DHA transport across the human placenta. Given the great importance of placental DHA transport for infant outcome, further studies are needed to fully appreciate the effects and optimal strategies of omega-3 fatty acid interventions in pregnancy, dose response relationships, and the potential differences between subgroups of subjects such as women with gestational diabetes or other gestational pathology. Such studies should contribute to optimize substrate intake during pregnancy and lactation that may improve pregnancy outcome as well as fetal growth and development.

Does fish oil prevent preterm birth?

A literature review was performed on the effect of fish oil on preterm birth in observational and randomized studies. The only weak effect on preterm birth found in meta-analyses could be caused by the low compliance, and the fact that many women stop supplementation before term together with a fast acting effect on fish oil.

Emerging drug therapies for preventing spontaneous preterm labor and preterm birth

Preterm birth (PTB) is the main cause of neonatal mortality and morbidity in the developed world. Historically, the approach for the prevention of PTB has been reactive rather than proactive. With the introduction of new screening tests and a greater emphasis on prevention rather than treatment, a number of new approaches have been introduced that show promise. Progesterone, which is responsible for myometrial quiescence in pregnancy and is used in women with a previous history of PTB, is associated with a significant reduction in the incidence of PTB and low birth weight. Infection is an important cause of PTB in < or = 40% of women. The appropriate antibiotics administered early in pregnancy to women with abnormal genital tract flora have been associated with a 40-60% reduction in the incidence of PTB. Although there has been debate regarding the benefits of nutritional supplementation for the prevention of many complications of pregnancy, recent evidence suggests that fish oil supplementation can be shown to reduce the incidence of PTB in women at risk of PTB. Although these three proactive, preventative approaches show promise, further research is needed to establish the best agent, the optimum gestational age at commencement and cessation, the ideal candidate patient to achieve a response and the long-term feto-maternal benefits and/or side effects.

Duration of pregnancy in relation to fish oil supplementation and habitual fish intake: a randomised clinical trial with fish oil

OBJECTIVE

To examine the effect of fish oil supplementation on duration of pregnancy, conditional on the woman's habitual fish intake.

DESIGN

Multicentre 1:1 randomised clinical trial of effect of fish oil in a high-risk population of pregnant women in whom habitual fish intake was assessed at randomisation.

SETTING

Nineteen university delivery wards in seven European countries.

SUBJECTS

Pregnant women with preterm delivery, intrauterine growth retardation (IUGR), or pregnancy-induced hypertension (PIH) in a previous pregnancy (group 1, n=495); with twin pregnancies (group 2, n=367); or with suspicion of IUGR or threatening preeclampsia in the current pregnancy (group 3, n=106). Women were stratified into low, middle, or high fish consumers.

METHODS

The intervention group received fish oil capsules providing 2.7 g long-chain n-3 fatty acids per day (n-3 poly unsaturated fatty acids (PUFA)) from around week 20 (groups 1 and 2) or 6.3 g n-3 PUFA from week 33 (group 3). The control regimen was capsules with olive oil. Effect on timing of spontaneous delivery was examined by Cox regression, assuming elective delivery (occurring in 40%) as a censoring event. Analyses of effect of fish oil were intention to treat, and all analyses were adjusted for maternal smoking, age, and parity.

RESULTS

In group 1, fish oil reduced the hazard rate of spontaneous delivery (HR) by 44% (95% confidence interval 14-64%) and 39% (16-56%) in low and middle fish consumers, respectively, with no detectable effect (-56 to 33%) in high fish consumers. In groups 2 and 3, no significant effect of fish oil was detected in any of the sub-strata defined by baseline fish consumption.

CONCLUSIONS

In pregnant women with previous pregnancy complications, fish oil supplementation delayed onset of delivery in low and middle, but not in high, fish consumers.

SPONSORSHIP

March of Dimes Birth Defects Foundation, Concerted Action (ERB-BMH1-CT92-1906) and PECO (ERB-CIPD-CT94-0235) programmes of the European Commission, and the Danish National Research Foundation. Lube Ltd donated the oil capsules.

Duration of pregnancy in relation to seafood intake during early and mid pregnancy: prospective cohort

We examined the association between exposure to seafood intake during two periods of pregnancy on the one hand and risks of preterm delivery and postterm delivery on the other. In a prospective cohort of 8729 pregnant Danish women, we assessed frequency of fish meals during the first and second trimester of pregnancy by questionnaires completed around gestation weeks 16 and 30, respectively. When fish intake was based solely on intake reported for the early period of pregnancy, mean gestation length was shorter by 3.91 (95% CI: 2.24-5.58) days and odds of preterm delivery were increased 2.38 (1.23-4.61) times in those who never consumed fish (n = 308) vs. those who consumed both fish as main meal and fish in sandwiches at least once per week (n = 785). These measures were similar when fish intake was based solely on intake reported for mid-pregnancy. In the subgroup of women reporting same intake in the two trimesters, those who never consumed fish (n = 165) had 8.57 (5.46-11.7) days shorter mean gestation and 19.6 (2.32-165) times increased odds of preterm delivery, compared to high fish consumers (n = 127); odds of elective and postterm delivery were reduced by a factor 0.33 (0.11-1.02) and 0.34 (0.12-0.95), respectively, in zero fish consumers. All analyses were adjusted for potential confounding by factors such as maternal smoking, height, and prepregnant weight. We conclude that never consuming fish in the first two trimesters of pregnancy was an extremely strong risk factor for preterm delivery but was also associated with reduced risks of elective delivery and postterm delivery.