This question comes up from time to time, and since inCYST is so big on flaxseed, it's a good idea to have information at your fingertips.
Around the Internet, caution regarding the use of flax while pregnant is easy to find. The rationale for this caution is that mothers and fetuses are especially sensitive to hormones.
The Internet is also full of advice from flaxseed manufacturers promoting its use, because it can be converted to DHA, which as this blog consistently discusses, is crucial for conception, pregnancy, and development of a healthy baby.
Neither of those assertions is totally correct.
I dove into Pub Med last night and looked for any research to support the advice against flax during pregnancy. I couldn't find it. What I DID find was a whole host of animal studies, primarily done on pigs and cows, with mostly positive findings. It's always important to remember that animal studies do not always extrapolate completely to humans, but they do give us an idea of what's going on.
Effects of flaxseed consumption during pregnancy (again, in pigs and cows) included:
--healthier immune systems in babies
--better growth in babies
--after having one baby, a shorter time to ovulation (restored fertility)
--breast milk with a higher omega-3 fatty acid content and a lower omega-6 to omega-3 fatty acid ratio
--higher brain omega-3 content in babies
--increased levels of EPA, another omega-3 important for prostaglandin function and healthy blood clotting
--higher pregnancy rates
--larger follicle size
--higher conception rates
--lower miscarriage rates
--higher progesterone levels
IMPORTANT DISCLAIMERS
While I'm always excited to report positive links between nutrition and fertility, you all should know when I look through the research I am actually searching hard for the BAD news. This is such a high-risk specialty! The very last thing I would want to do is encourage our readers to make choices leading to frustration, disappointment, heartache, and loss of our own credibility. So I want to make it clear, the benefits of flax can be achieved only if it's used with respect.
Flax cannot replace fish oil. Some flax supplement manufacturers promote its use because it is converted into DHA and therefore can be used as a supplement for flax. Not true! The studies I perused found different effects for both, meaning you need both in your diet.
If your diet is imbalanced, flax won't make up for it. One study I found showed that when protein intake was low, flax supplementation was not beneficial. This would be a scenario not uncommon with our vegetarian readers, if their definition of vegetarian eating focuses more on what to eliminate rather than what to include, or is the remnant of an eating disorder. As always, supplements work best in a well-nourished environment; they cannot replace balanced, nourished eating.
Finally, if you choose to use flax…IT MUST BE GROUND. In other words, the flaxseed tortilla chips at Trader Joe's were not what made these studies work.: )
I've heavily referenced this post to save the skeptics the work.
I hope you find this helpful!
Rao SS, Kale AA, Joshi SR, Mahadik SP. Sensitivity of fetus and pups to excess levels of maternal intakes of alpha linolenic acid at marginal protein levels in Wistar rats. Reprod Toxicol. 2007 Nov-Dec;24(3-4):333-42. Epub 2007 Jul 28.
Yu B, Khan G, Foxworth A, Huang K, Hilakivi-Clarke L. Maternal dietary exposure to fiber during pregnancy and mammary tumorigenesis among rat offspring. Int J Cancer. 2006 Nov 15;119(10):2279-86.
Ambrose DJ, Kastelic JP, Corbett R, Pitney PA, Petit HV, Small JA, Zalkovic P. Lower pregnancy losses in lactating dairy cows fed a diet enriched in alpha-linolenic acid. J Dairy Sci. 2006 Aug;89(8):3066-74.
Petit HV, Twagiramungu H. Conception rate and reproductive function of dairy cows fed different fat sources. Theriogenology. 2006 Sep 15;66(5):1316-24. Epub 2006 Jun 2.
Farmer C, Giguère A, Lessard M. Dietary supplementation with different forms of flax in late gestation and lactation: Effects on sow and litter performances, endocrinology, and immune response. J Anim Sci. 2010 Jan;88(1):225-37. Epub 2009 Sep 25.
Colazo MG, Hayirli A, Doepel L, Ambrose DJ. Reproductive performance of dairy cows is influenced by prepartum feed restriction and dietary fatty acid source. J Dairy Sci. 2009 Jun;92(6):2562-71.
Farmer C, Petit HV. Effects of dietary supplementation with different forms of flax in late-gestation and lactation on fatty acid profiles in sows and their piglets. J Anim Sci. 2009 Aug;87(8):2600-13. Epub 2009 Apr 24.
Brazle AE, Johnson BJ, Webel SK, Rathbun TJ, Davis DL. Omega-3 fatty acids in the gravid pig uterus as affected by maternal supplementation with omega-3 fatty acids. J Anim Sci. 2009 Mar;87(3):994-1002. Epub 2008 Nov 7.
Galbreath CW, Scholljegerdes EJ, Lardy GP, Odde KG, Wilson ME, Schroeder JW, Vonnahme KA. Effect of feeding flax or linseed meal on progesterone clearance rate in ovariectomized ewes.
Domest Anim Endocrinol. 2008 Aug;35(2):164-9. Epub 2008 Jun 5.