Table 1.
Demographic and Reproductive Characteristics at Baseline According to Quartiles of Estimated Nitrogen Dioxide Exposure in the 3 Months Prior to Assisted Reproductive Technology Use and Intake of Supplemental Folate Among 304 Women in the Environment and Reproductive Health Study, Massachusetts, 2005–2015
| Characteristic | Women Who Consumed <800 μg/day of Supplemental Folate (n = 173) | Women Who Consumed ≥800 μg/day of Supplemental Folate (n = 131) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| NO2 Quartile 1 (n = 44) | NO2 Quartile 4 (n = 47) | NO2 Quartile 1 (n = 32) | NO2 Quartile 4 (n = 29) | |||||||||
| Mean (SD) | No. | % | Mean (SD) | No. | % | Mean (SD) | No. | % | Mean (SD) | No. | % | |
| Estimated NO2 exposure, ppb | 8.8 (3.1) | 56.9 (37.2) | 8.3 (4.4) | 58.4 (57.0) | ||||||||
| Demographic characteristics | ||||||||||||
| Age, years | 35.1 (4.0) | 35.0 (4.1) | 35.1 (4.5) | 35.3 (4.4) | ||||||||
| White race | 37 | 84.1 | 40 | 85.1 | 29 | 90.6 | 24 | 82.8 | ||||
| BMIa | 25.5 (5.2) | 23.9 (4.1) | 25.2 (4.3) | 23.6 (3.8) | ||||||||
| Smoking status | ||||||||||||
| Never | 32 | 72.7 | 32 | 68.1 | 23 | 71.9 | 21 | 72.4 | ||||
| Former | 9 | 20.5 | 14 | 29.8 | 9 | 28.1 | 7 | 24.1 | ||||
| Current | 3 | 6.8 | 1 | 2.1 | 0 | 0.0 | 1 | 3.5 | ||||
| Educational level | ||||||||||||
| High school or less | 5 | 11.4 | 4 | 8.5 | 3 | 9.4 | 1 | 3.5 | ||||
| College | 13 | 29.0 | 13 | 27.7 | 16 | 50.0 | 5 | 17.2 | ||||
| Graduate school | 26 | 59.1 | 30 | 63.8 | 13 | 40.6 | 23 | 79.3 | ||||
| Distance to A1–A3 roadway, m | 279.7 (337.3) | 129.4 (105.1) | 517.3 (627.5) | 78.5 (75.9) | ||||||||
| Census tract median income, $ | 105,327 (31,418) | 95,474 (45,496) | 99,071 (31,182) | 101,610 (42,076) | ||||||||
| Dietary characteristics | ||||||||||||
| Total calories, kcal/day | 1,877.0 (625.8) | 1,834.3 (609.0) | 1,807.7 (586.8) | 1,705.7 (648.0) | ||||||||
| Total folate, μg/day | 797.5 (291.0) | 808.9 (308.3) | 1,387.5 (337.7) | 1,408.1 (294.5) | ||||||||
| Food folate, μg/day | 459.1 (202.7) | 483.6 (168.4) | 422.9 (211.7) | 454.2 (225.3) | ||||||||
| Supplemental folate, μg/day | 338.4 (194.2) | 325.3 (218.8) | 964.5 (305.7) | 953.9 (210.4) | ||||||||
| Alcohol intake, g/day | 9.0 (14.3) | 12.3 (13.3) | 7.7 (9.3) | 7.4 (5.6) | ||||||||
| aHEI-2010 score | 62.9 (11.0) | 68.0 (10.1) | 62.9 (12.5) | 69.0 (9.8) | ||||||||
| Baseline reproductive characteristics | ||||||||||||
| Duration of pregnancy attempt, months | ||||||||||||
| ≤12 | 8 | 18.2 | 20 | 42.6 | 11 | 34.4 | 6 | 20.7 | ||||
| 13–24 | 25 | 56.8 | 21 | 44.7 | 14 | 43.8 | 15 | 51.7 | ||||
| ≥24 | 11 | 25.0 | 6 | 12.8 | 7 | 21.9 | 8 | 27.6 | ||||
| Previous IVF cycle at MGH | 13 | 29.6 | 5 | 10.6 | 10 | 31.3 | 5 | 17.2 | ||||
| Nulligravid | 27 | 61.4 | 31 | 66.0 | 18 | 56.3 | 17 | 58.6 | ||||
| Nulliparous | 38 | 86.4 | 42 | 89.4 | 24 | 75.0 | 26 | 89.7 | ||||
| Infertility diagnosis | ||||||||||||
| Male factor | 13 | 29.6 | 17 | 36.2 | 7 | 21.9 | 7 | 24.1 | ||||
| Female | 15 | 34.1 | 13 | 27.7 | 9 | 28.1 | 12 | 41.4 | ||||
| Unexplained | 16 | 36.4 | 17 | 36.2 | 16 | 50.0 | 10 | 34.5 | ||||
| Protocol | ||||||||||||
| Antagonist or flare | 9 | 20.5 | 11 | 23.4 | 9 | 28.1 | 2 | 6.9 | ||||
| Luteal phase agonist | 29 | 65.9 | 33 | 70.2 | 20 | 62.5 | 24 | 82.8 | ||||
| Egg-donor or cryo-thaw cycle | 6 | 13.6 | 3 | 6.4 | 3 | 9.4 | 3 | 10.3 | ||||
| Number of ART cycles contributed to analysis | 1.8 (1.0) | 1.9 (1.1) | 1.4 (0.8) | 1.6 (1.0) | ||||||||
Abbreviations: aHEI-2010, alternate Health Eating Index 2010; ART, assisted reproductive technology; BMI, body mass index; IVF, in vitro fertilization; MGH, Massachusetts General Hospital; NO2, nitrogen dioxide; ppb, parts per billion; SD, standard deviation.
a BMI was calculated as weight (kg)/height (m)2.