Yes it is safe...insurance companies advise therapist's not to spray clients who are in their first trimester as a precaution because it is the most risky stage of any pregnancy.
DHA (the tanning agent in spray-tans) is a natural substance and is only toxic if inhaled, in large quantities. Essentail oils can also be toxic but are also amazingly beneficial when used correctly.
Hope this helps.
Ps - I offer a selection of tans (Organic, Express, Light - Medium etc.) In the comfort of your own home; around the london area.