Would a blood test before missed period still be accurate?

Pregnancy. Great majority of pregnancies occur when coitus takes places within the 3 day interval just prior to ovulation. The first hormonal evidence of implantation (appearance of hcg) ocurred on 8 to 10 days after ovulation. However some commercial urine tests only detect pregnancy 5 days before your missed period. However if negative and still suspect a pregnancy, consider doing a blood HCG level.