Table 2. Baseline characteristics of the study population (categorical variables)
Variable Absolute Frequency(n) Relative Frequency(%) Total Available(n)
Female smokinga - Yes 8 5.4 147
Male smokinga - Yes 11 8.9 124
Infertility - Primary 79 44.3 178
Infertility - Secondary 106 59.5 178
Endometriosis - Present 45 22.9 196
Stimulation protocol - Progestin 144 60.8 237
Stimulation protocol - GnRH antagonist 93 39.2 237

a Female and male smoking status was defined according to documented tobacco use in the medical records, regardless of the duration of exposure.