Does consuming sodium benzoate (preservative E211) cause problems during pregnancy?
There is some evidence to support the idea that sodium benzoate may be detrimental to the development of the foetus:

TERATOGENIC EFFECTS: Classified POSSIBLE for human.
DEVELOPMENTAL TOXICITY: Classified Reproductive system/toxin/female, Reproductive system/ toxin/male [SUSPECTED].

MSDS for Sodium Benzoate
This has been shown experimentally in rats by Minor &amp; Becker in 1971.  They introduced high doses of up to 1000 mgkg-1 intraperitoneally and recorded reduction in foetal weight and &quot;gross anomalies&quot;.  Whilst I struggled to find a copy of their original paper, it is referenced in the Catalog of Teratogenic Agents1 (Thomas H. Shepard).
There is some evidence to refute this, however.  The Acceptable Daily Intake limits on sodium benzoate is a maximum of 5mgkg-1, at this dose there is no noticeable effect of exposure. (2,3)  The latter paper by EC food safety standards goes further:

There appear to be sufficient studies to conclude absence of teratogenic potential, with an overall NOAEL* for developmental toxicity of 500 mg/kg bw/day, based on effects on fetal weight.

*(No observed adverse effect level)
So the consensus from the food safety bodies suggests that E211 should not pose harm to an unborn child in the quantities allowed to be present as an additive.

1 Emire, Ronald J. &quot;306: Benzoate, Sodium.&quot; Catalog of Teratogenic Agents. By Thomas H. Shepherd. JHU, 2004. 44-45. Google Books. Google. Web. 10 Feb. 2012.
2 Nair, B. &quot;Final Report on the Safety Assessment of Benzyl Alcohol, Benzoic Acid, and Sodium Benzoate.&quot; International Journal of Toxicology 20.3 (2001). International Journal of Toxicology. Web. 10 Feb. 2012.
3 Scientific Committee on Food. Opinion of the Scientific Committee on Food on Benzoic acid and its salts. Rep. 24 Sept. 2002. EUROPEAN COMMISSION HEALTH &amp; CONSUMER PROTECTION DIRECTORATE-GENERAL. 10 Feb. 2012