Distribution of time to pregnancies in menstrual cycle and potential confounding factors by blood lead level in men at the beginning of the calendar year when time to pregnancy started
| Non-exposed | Blood lead level (μg/dl) | Total | ||||
|---|---|---|---|---|---|---|
| <20 | 20–29 | 30–39 | ⩾40 | |||
| TTP, time to pregnancy. | ||||||
| Total number | 153 | 31 | 25 | 34 | 37 | 280 |
| Time to pregnancy (cycles) | ||||||
| 1 | 52 | 5 | 1 | 3 | – | 61 |
| 2 | 36 | 3 | 2 | 3 | 2 | 45 |
| 3–4 | 28 | 11 | 8 | 5 | 5 | 58 |
| 5–6 | 21 | 7 | 9 | 6 | 7 | 50 |
| 7–12 | 14 | 5 | 4 | 15 | 21 | 59 |
| ⩾13 | 2 | – | 1 | 2 | 2 | 7 |
| Mean | 3.4 | 4.1 | 5.3 | 6.4 | 8.1 | 4.6 |
| Median | 2.0 | 3.0 | 5.0 | 6.5 | 8.0 | 4.0 |
| Male factors | ||||||
| Age at the beginning of TTP (y) | ||||||
| 18–24 | 31 | 8 | 6 | – | 1 | 46 |
| 25–29 | 71 | 11 | 11 | 19 | 16 | 128 |
| 30–38 | 51 | 12 | 8 | 15 | 20 | 106 |
| Job title | ||||||
| In situ production | 128 | 10 | 12 | 27 | 27 | 204 |
| Administrative | 12 | 15 | 10 | 3 | – | 40 |
| Supervisor | 6 | 2 | 2 | 1 | 3 | 14 |
| Others | 7 | 4 | 1 | 3 | 7 | 22 |
| Duration of employment (y) | ||||||
| Mean (SD) | 3.7 (1.6) | 3.3 (1.7) | 2.8 (1.5) | 2.7 (1.8) | 3.2 (1.5) | 3.4 (1.6) |
| Smoking (cigarettes/day) | ||||||
| 1–10 | 40 | 7 | 8 | 12 | 6 | 76 |
| >10 | 70 | 9 | 12 | 14 | 19 | 124 |
| Use of alcohol (drinks/week) | ||||||
| 1–2 | 59 | 4 | 7 | 10 | 10 | 90 |
| ⩾3 | 20 | 2 | 1 | 1 | 2 | 26 |
| Use of tea or coffee (cups/day) | ||||||
| 1–2 | 41 | 9 | 6 | 14 | 8 | 78 |
| ⩾3 | 17 | 1 | 3 | 4 | 7 | 32 |
| Female factors | ||||||
| Age at the beginning of TTP | ||||||
| 18–24 | 73 | 8 | 11 | 14 | 9 | 115 |
| 25–29 | 56 | 19 | 9 | 16 | 24 | 124 |
| 30–34 | 24 | 4 | 5 | 4 | 4 | 41 |
| Lead exposure at the beginning of TTP | ||||||
| Yes | 3 | 1 | 6 | 3 | 4 | 17 |
| Shift work | ||||||
| Yes | 63 | 16 | 11 | 10 | 19 | 119 |
| Smoking (cigarettes/day) | ||||||
| 1–10 | 19 | 6 | 4 | 4 | 6 | 39 |
| Use of alcohol (times/week) | ||||||
| 1–2 | 32 | 3 | 5 | 2 | 5 | 47 |
| Use of tea or coffee (cups/day) | ||||||
| 1–2 | 27 | 6 | 4 | 1 | 1 | 39 |
| ⩾3 | 11 | 2 | 1 | 2 | 5 | 21 |
| Menarche (y) | ||||||
| ⩽13 | 24 | 9 | 6 | 5 | 6 | 50 |
| 14–16 | 121 | 20 | 17 | 27 | 29 | 214 |
| ⩾17 | 8 | 2 | 2 | 2 | 2 | 16 |
| Number of pregnancies | ||||||
| Mean (SD) | 2.4 (1.2) | 2.3 (1.1) | 2.3 (1.3) | 2.1 (1.2) | 2.0 (1.3) | 2.3 (1.2) |
| Contraceptive use before TTP | ||||||
| Intrauterine device | 18 | 4 | 3 | 5 | 5 | 35 |
| Pill | 12 | 2 | 3 | 4 | 3 | 24 |
| Condom | 52 | 10 | 7 | 12 | 15 | 96 |
| None | 71 | 14 | 12 | 13 | 14 | 124 |
| Year of the pregnancy | ||||||
| 1985–89 | 43 | 9 | 5 | 8 | 10 | 75 |
| 1990–94 | 61 | 6 | 7 | 13 | 15 | 102 |
| 1995–99 | 49 | 16 | 13 | 13 | 12 | 103 |
| Sequence of the pregnancy | ||||||
| 1 | 67 | 17 | 13 | 11 | 7 | 115 |
| ⩾2 | 86 | 14 | 12 | 23 | 30 | 165 |