Purpose: To determine if a mid-luteal phase non-homogeneous hyperechogenic (HH) endometrial echo pattern may lower pregnancy rates following frozen embryo transfer and to determine if raising the dosage of progesterone improves pregnancy outcome. Methods: Women not attaining an HH pattern at the mid-luteal phase following estrogen-progesterone replacement were randomly given (or not) an increase in progesterone dosage. Results: Increasing the progesterone dosage in those not attaining an HH pattern significantly improved the pregnancy rate relative to controls not attaining an HH pattern and showed a trend for higher pregnancy rates than those with an HH pattern. Conclusions: The mid-luteal phase echo pattern should be evaluated for a non-HH pattern so that an increase in progesterone dosage could be provided possibly resulting in higher pregnancy rates.