It's a long time since I was pregnant but fairly recently I ate blueberries and they gave me horrible stomach pain and diarrhoea. So I googled them and discovered that you can be allergic to them and they shouldn't be given to babies under 9 months old, so maybe eating them when pregnant is relevant? Here's the list of potential reactions:
Blueberries contain salicylates, which are natural-occurring chemicals in plants. This compound is what causes most allergic reactions to blueberries. Salicylates are found in other foods and products so if you are found to be allergic, consider staying away from products that contain salicylates.
While fresh blueberries may have a slightly laxative effect upon the body, when dried they are astringent and commonly used in the treatment of diarrhea, cystitis, and similar ailments.
Symptoms of an allergic reaction to blueberries may be:
Itching
Swelling
Hives, swelling, or redness
Abdominal pain
Nausea
Vomiting
Diarrhea
Runny or stuffy nose
Coughing
Sneezing
Wheezing
Difficulty breathing
Drop-in blood pressure
Lightheadedness
Fainting
Anaphylaxis (rare life-threatening allergic reaction)