I have irregular periods, could that effect the results of a urine pregnancy test?

No : The urine pregnancy test is not affected by the pattern of your periods. It is just harder to know when the best time is to use it.

See below: Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.