妊娠期补充鱼油以改善妊娠结局
生物学、行为学和背景依据
ω-3脂肪酸是维持人体健康和发育必需的长链多不饱和脂肪酸。与植物（如，亚麻子和油菜籽油）来源的ω-3脂肪酸不同，鱼油和海藻油含有长链二十二碳六烯酸（DHA）和二十碳五烯酸（EPA）。DHA和EPA被称为必需脂肪酸，因为人体自身不能生成，所以，人体须摄取足够的必需脂肪酸。
产前期孕妇体内组织所储备的ω-3脂肪酸被用于胎儿发育，造成储量趋于下降 1 导致孕妇发生ω-3脂肪酸缺乏的风险升高2, 3. 通常建议孕妇补充鱼油/海藻油，以满足其对ω-3脂肪酸的需求。
研究认为妊娠期补充鱼油/海藻油可作为一项可能的策略，用于预防早产（或延长胎龄）和子痫以及提高胎儿出生体重，其它潜在益处包括改善胎儿脑发育、降低脑瘫和产后抑郁的风险 4–7. 关于生育结局研究的理论依据是根据观察结果得出的，这些研究发现:大量食用鱼类的社区中新生儿的出生体重较大、胎龄较长 8–10.
鱼油/海藻油中所含的DHA和EPA是前列腺素的前体物质，研究发现前列腺素可影响血管收缩。服用鱼油/海藻油治疗高血压已在孕妇和非妊娠妇女中得到推广11. 这些鱼油成分也可延后分娩，因此通过抑制可促进宫颈成熟的前列腺素的生成有可能延长孕期，增加胎儿出生体重 12.
也有一些研究探讨了上述机制及其对孕产妇和儿童健康的潜在益处，但得出的结果并不一致 4, 5, 10, 13, 14. 近期一项系统综述得出了令人振奋的结论：虽然目前尚无充分的证据支持妊娠期常规补充鱼油/海藻油可降低先兆子痫、早产或低出生体重的风险，但作为延长孕期的一个手段，补充鱼油/海藻油能使孕妇获益12.
在制订关于孕妇补充鱼油/海藻油的营养建议时，应同时给出限制鱼类摄取总量的警示。虽然鱼类是ω-3脂肪酸的重要来源，但有多种鱼类可能已被甲基汞或聚氯联(二)苯污染 （PCB），反而会危害胎儿发育 15, 16. 这些潜在有害的污染物更多地蓄积于鱼肉内，在鱼油中相对较少。然而孕妇摄取未经提炼的鱼油制品时也可能存在安全性问题，因为这些制品中可能含有农药和PCB残留物 17.
来自鱼油/海藻油的DHA和EPA的剂量，依据孕产妇和儿童需要多少DHA和EPA才能获得潜在益处而不同,。研究试验中所使用的DHA和EPA的剂量为每日133毫克至3克不等，其中多数妇女每日约摄入2.7克EPA和DHA 12. 如果把这一摄入量换算为食物来源，则孕妇每日须摄入300克熟制三文鱼；由于妊娠期女性可能接触到污染物，这可能不一定符合孕妇限制食用鱼类的警示。补充鱼油似乎不会引起严重的副作用（如出血并发症或不适），但与孕妇偶尔抱怨的口感不好相比，严重的副作用更易影响依从性 12, 18, 19.
参考文献
1 Makrides M, Gibson R.S. Long-chain polyunsaturated fatty acid requirements during pregnancy and lactation. American Journal of Clinical Nutrition, 2000, 71:307S–311S.
2 Al MD et al. Maternal essential fatty acid patterns during normal pregnancy and their relationship to the neonatal essential fatty acid status. British Journal of Nutrition, 1995, 74:55–68.
3 Otto SJ et al. Maternal and neonatal fatty acid status in phospholipids: an international comparative study. European Journal of Clinical Nutrition, 1997, 51:232–242.
4 Olafsdottir AS et al. Relationship between dietary intake of cod liver oil in early pregnancy and birthweight. British Journal of Obstetrics and Gynaecology, 2005, 112:424–429.
5 Ramakrishnan U et al. Effects of docosahexaenoic acid supplementation during pregnancy on gestational age and size at birth: randomized, double-blind, placebo-controlled trial in Mexico. Food and Nutrition Bulletin, 2010, 31:S108–S116.
6 Petridou E et al. Diet during pregnancy and the risk of cerebral palsy. British Journal of Nutrition, 1998, 79:407–412.
7 Borja-Hart NL, Marino J. Role of omega-3 fatty acids for prevention or treatment of perinatal depression. Pharmacotherapy, 2010, 30:210–216.
8 Olsen SF, Joensen HD. High liveborn birth weights in the Faroes: a comparison between birth weights in the Faroes and in Denmark. Journal of Epidemiology and Community Health, 1985, 39:27–32.
9 Olsen SF, Hansen HS. Marine fat, birthweight, and gestational age: a case report. Agents Actions, 1987, 22:373–374.
10 Olsen SF et al. Randomized controlled trial of effect of fish-oil supplementation on pregnancy duration. The Lancet, 1992, 339:1003–1007.
11 Morris MC et al. Does fish oil lower blood pressure? A meta-analysis of controlled trials. Circulation, 1993, 88:523–533.
12 Makrides M et al. 等.未伴发先兆子痫或胎儿宫内生长迟缓的孕妇补充鱼油及其它前列腺素前体物质. Cochrane 系统综述数据库, 2006, 第3期, 文件编号: CD003402.
13 Harper M et al. Omega-3 fatty acid supplementation to prevent recurrent preterm birth. Obstetrics and Gynecology, 2010, 115:234–242.
14 Williams MA et al. Omega-3 fatty acids in maternal erythrocytes and risk of preeclampsia. Epidemiology, 1995, 6:232–237.
15 Nutrition in pregnancy: Scientific Advisory Committee Opinion Paper 18. London, Royal College of Obstetricians and Gynaecologists, 2010.
16 Buck GM et al. Maternal fish consumption and infant birth size and gestation: New York State angler cohort study. Environmental Health, 2003, 2:7–16.
17 Rawn DFK et al. Persistent organic pollutants in fish oil supplements on the Canadian market: polychorinated biphenyls and organochlorine insecticides. Journal of Food Science, 2008, 74:T14–T19.
18 Makrides M. Is there a dietary requirement for DHA in pregnancy? Prostaglandins, Leukotrienes and Essential Fatty Acids, 2009, 81:171–174.
19 Akabas SR, Deckelbaum RJ. Summary of a workshop on n-3 fatty acids: current status of recommendations and future directions. American Journal of Clinical Nutrition, 2006, 83:1536S–1538S.