Fig. 2
From: The natural menstrual cycle revisited – can natural cycle be trusted
Correlation between AUC (progesterone levels) and a serum progesterone level ≥ 30 nmol/L on cycle day 20 or 25. Participants less than 35 years old. AUC: area under the curve from day 14 to 25 or 30 (progesterone levels). Blue dot represents serum progesterone levels ≥ 30 nmol/L on cycle day 20 or 25. Red dot represents serum progesterone levels < 30 nmol/L on cycle day 20 and 25. Blue line represents a participant with serum progesterone levels ≥ 30 nmol/L on cycle day 20 or 25 in all three cycles. Red line represents a participant with 0, 1 or 2 cycles with serum progesterone levels ≥ 30 nmol/L on cycle day 20 or 25 out of the three cycles