Table 1 Characteristics and results of included studies concerned caffeine intake with infertility

20-54y

≥100 mg/d

0 mg/d

OR = 0.91 (0.46–1.82)

Unclear

E₁ 100-167mg/d; E₂ 168-233mg/d;

E₃>233mg/d

<100 mg/d

OR₁ = 1.00(0.79–1.25);

OR₂ = 1.16(0.94–1.42);

OR₃ = 1.36(1.16–1.60) ^a,b

Median 31-33y

E₁ 200-300 mg/d; E₂ ≥ 400 mg/d

0-100 mg/d

OR₁ = 1.7(0.8–3.7);

OR₂ = 5.4 (2.4–12.6) ^c

20-29y

Coffee:

E₁ ≤ 200 ml/d

E₂ 200-400 ml/d

E₃ ≥ 500 ml/d

0 ml/d

HR₁ = 0.86(0.70–1.06);

HR₂ = 0.88(0.73–1.06);

HR₃ = 0.89(0.72–1.10);

Tea:

E₁ ≤ 200 ml/d

E₂ 200-400 ml/d

E₃ ≥ 500 ml/d

0 ml/d

HR₁ = 1.10(0.84–1.44);

HR₂ = 1.10(0.84–1.46);

HR₃ = 1.15(0.87–1.53);

Caffeine^d:

E₁ ≤ 1-168 mg/d

E₂ 169-333mg/d

E₃ 334-579mg/d

E₄ ≥ 580 mg/d

0 mg/d

HR₁ = 0.93(0.58–1.49);

HR₂ = 0.91(0.57–1.47);

HR₃ = 0.97(0.60–1.55);

HR₄ = 0.93(0.58–1.50)^e