Hi Paulina.
I agree with Ruslan in terms of whether it is OK from a ranking perspective.
However, it is critical to remember that your meta data has another important objective - to entice searchers to click through to your page.
A well written meta description makes a considerable difference to click-through rates.
Consider spending as long on your page meta data as you would when trying to write an effective Adwords Ad.
In consideration of this objective (maximising click through rates), you may find that the first sentence or two of your body copy would not suffice as an effective meta description.
cheers, David.