Figure 2. Mean daily PdG (A,B) and E₁C (C,D) levels in the 20-day window around ovulation by the status of ETS exposure. Of 344 total nonconception cycles (A,C), 44 had no ETS exposure and 300 had ETS exposure; of 329 total conception cycles (B,D), 32 had no ETS exposure and 297 had ETS exposure.