Geometric means, median, and selected percentiles (95% confidence interval in parentheses) for SF (μg/L) concentrations in an apparently healthy sample of US pregnant women aged 15 to 49 years participating in the NHANES 1999 to 2010 and 2015 to 2018.
| . | n . | Unadjusted geometric mean∗ . | Adjusted geometric mean∗ . | Median . | 5th percentile . | 95th percentile . |
|---|---|---|---|---|---|---|
| Total | 1288 | 22.4 (20.7-24.3) | — | 22.7 (20.3-25.9) | 4.7 (3.6-6.1) | 98.8 (82.9-110.4) |
| Survey year | ||||||
| 1999-2000 | 249 | 17.8 (14.6-21.7)† | 17.1 (13.8-21.4)† | 14.7 (12.4-21.4) | – (–,–) | 81.0 (67.5-114.3) |
| 2001-2002 | 308 | 21.0 (18.1-24.2)† | 18.9 (16.6-21.9)† | 21.3 (17.4-25.9) | 3.9 (– to 5.4) | 80.8 (53.9-107.1) |
| 2003-2004 | 233 | 26.6 (23.2-30.6)‡ | 27.7 (24.0-31.6)‡ | 29.4 (21.8-31.8) | 7.3 (5.8-8.3) | 98.1 (68.0-109.1) |
| 2005-2006 | 339 | 23.8 (19.7-28.7)† | 24.8 (20.9-29.5)† | 23.3 (19.6-29.8) | 4.7 (4.5-4.9) | 110.4 (68.3-141.0) |
| 2007-2010 and 2015-2018 | 159 | 24.6 (21.1-28.8)† | 24.5 (20.9-28.8)† | 23.0 (20.0-28.9) | 5.8 (3.7-9.0) | 95.1 (74.7-111.1) |
| Age | ||||||
| 15-24 y | 513 | 18.4 (16.3-20.8)† | 17.4 (15.5-19.5)† | 18.0 (16.0-22.6) | 3.7 (– to 6.1) | 72.3 (54.7-102.6) |
| 25-29 y | 372 | 23.4 (20.3-27.0)‡ | 23.6 (20.4-27.5)‡ | 23.2 (19.2-29.8) | 4.9 (3.1-6.9) | 99.9 (68.6-116.0) |
| 30-49 y | 403 | 25.8 (22.2-30.0)‡ | 25.7 (21.9-30.2)‡ | 26.7 (22.2-32.5) | 5.1 (– to 7.7) | 109.3 (86.2-120.8) |
| Trimester | ||||||
| First | 202 | 42.4 (36.7-49.0)† | 41.5 (36.3-47.9)† | 44.2 (38.6-53.2) | 8.1 (5.9-15.0) | 111.3 (102.4-114.8) |
| Second | 430 | 22.6 (19.0-26.9)‡ | 22.2 (19.5-25.7)‡ | 23.5 (17.3-27.8) | 4.2 (– to 6.1) | 85.5 (72.6-114.6) |
| Third | 408 | 13.4 (11.8-15.2)c | 13.1 (11.8-14.8)c | 13.1 (12.0-15.9) | 3.7 (– to 5.0) | 35.4 (31.7-38.8) |
| Unknown | 248 | 25.3 (20.6-31.0)‡ | 26.4 (20.0-35.5)‡ | 28.0 (20.5-34.3) | 4.8 (– to 8.0) | 95.5 (77.4 to –) |
| Parity | ||||||
| 0 | 380 | 24.6 (20.5-29.6)† | 25.2 (21.4-29.5)† | 26.0 (20.9-30.9) | 5.3 (– to 8.4) | 88.8 (70.3-109.1) |
| 1 | 410 | 22.7 (19.8-25.9)† | 23.2 (20.4-26.3)† | 22.4 (17.7-28.6) | 5.0 (3.6-7.1) | 109.1 (78.8-137.7) |
| ≥2 | 388 | 18.7 (16.4-21.4)† | 18.4 (16.2-20.9)b | 18.8 (15.9-21.9) | 3.3 (– to 5.8) | 94.3 (68.4-110.5) |
| Race/ethnicity | ||||||
| Mexican American | 384 | 19.4 (17.2-21.9)† | 19.7 (17.4-22.4)† | 19.7 (16.8-22.0) | 3.3 (– to 4.7) | 81.8 (67.0-93.3) |
| Non-Hispanic White | 537 | 24.4 (21.6-27.6)‡ | 22.8 (20.4-25.7)† | 25.0 (21.7-30.0) | 4.6 (3.0-6.0) | 107.4 (79.1-113.6) |
| Non-Hispanic Black | 209 | 20.0 (16.3-24.6)† | 20.4 (16.6-24.6)† | 20.4 (12.1-26.1) | 5.6 (4.4-6.6) | 104.0 (65.7-119.7) |
| All others | 158 | 21.9 (18.2-26.4)† | 24.0 (20.4-28.2)† | 21.5 (15.8-30.0) | 5.2 (– to 8.0) | 93.2 (57.7-104.5) |
| Education | ||||||
| Less than high school | 398 | 20.7 (17.6-24.3)† | 23.8 (19.1-29.5)† | 21.3 (16.1-28.6) | 4.7 (4.6-5. 7) | 72.1 (56.7-84.4) |
| High school diploma | 284 | 20.9 (17.6-24.9)† | 21.1 (17.8-24.6)† | 21.4 (16.1-29.3) | 3.2 (– to 5.6) | 78.9 (65.2-100.7) |
| More than high school | 586 | 24.1 (21.2-27.5)† | 21.8 (19.5-24.6)† | 23.6 (20.5-28.8) | 5.0 (– to 7.6) | 109.5 (88.2 to –) |
| Family income | ||||||
| <130% of poverty income ratio | 440 | 19.9 (17.1-23.1)† | 21.7 (18.6-25.7)† | 20.6 (16.8-25.5) | 4.0 (3.1-6.2) | 68.7 (61.0-76.0) |
| ≥130% of poverty income ratio | 755 | 23.3 (20.9-25.9)† | 22.2 (20.4-24.0)† | 22.9 (20.2-27.9) | 4.7 (– to 6.4) | 107.7 (87.3-114.3) |
| . | n . | Unadjusted geometric mean∗ . | Adjusted geometric mean∗ . | Median . | 5th percentile . | 95th percentile . |
|---|---|---|---|---|---|---|
| Total | 1288 | 22.4 (20.7-24.3) | — | 22.7 (20.3-25.9) | 4.7 (3.6-6.1) | 98.8 (82.9-110.4) |
| Survey year | ||||||
| 1999-2000 | 249 | 17.8 (14.6-21.7)† | 17.1 (13.8-21.4)† | 14.7 (12.4-21.4) | – (–,–) | 81.0 (67.5-114.3) |
| 2001-2002 | 308 | 21.0 (18.1-24.2)† | 18.9 (16.6-21.9)† | 21.3 (17.4-25.9) | 3.9 (– to 5.4) | 80.8 (53.9-107.1) |
| 2003-2004 | 233 | 26.6 (23.2-30.6)‡ | 27.7 (24.0-31.6)‡ | 29.4 (21.8-31.8) | 7.3 (5.8-8.3) | 98.1 (68.0-109.1) |
| 2005-2006 | 339 | 23.8 (19.7-28.7)† | 24.8 (20.9-29.5)† | 23.3 (19.6-29.8) | 4.7 (4.5-4.9) | 110.4 (68.3-141.0) |
| 2007-2010 and 2015-2018 | 159 | 24.6 (21.1-28.8)† | 24.5 (20.9-28.8)† | 23.0 (20.0-28.9) | 5.8 (3.7-9.0) | 95.1 (74.7-111.1) |
| Age | ||||||
| 15-24 y | 513 | 18.4 (16.3-20.8)† | 17.4 (15.5-19.5)† | 18.0 (16.0-22.6) | 3.7 (– to 6.1) | 72.3 (54.7-102.6) |
| 25-29 y | 372 | 23.4 (20.3-27.0)‡ | 23.6 (20.4-27.5)‡ | 23.2 (19.2-29.8) | 4.9 (3.1-6.9) | 99.9 (68.6-116.0) |
| 30-49 y | 403 | 25.8 (22.2-30.0)‡ | 25.7 (21.9-30.2)‡ | 26.7 (22.2-32.5) | 5.1 (– to 7.7) | 109.3 (86.2-120.8) |
| Trimester | ||||||
| First | 202 | 42.4 (36.7-49.0)† | 41.5 (36.3-47.9)† | 44.2 (38.6-53.2) | 8.1 (5.9-15.0) | 111.3 (102.4-114.8) |
| Second | 430 | 22.6 (19.0-26.9)‡ | 22.2 (19.5-25.7)‡ | 23.5 (17.3-27.8) | 4.2 (– to 6.1) | 85.5 (72.6-114.6) |
| Third | 408 | 13.4 (11.8-15.2)c | 13.1 (11.8-14.8)c | 13.1 (12.0-15.9) | 3.7 (– to 5.0) | 35.4 (31.7-38.8) |
| Unknown | 248 | 25.3 (20.6-31.0)‡ | 26.4 (20.0-35.5)‡ | 28.0 (20.5-34.3) | 4.8 (– to 8.0) | 95.5 (77.4 to –) |
| Parity | ||||||
| 0 | 380 | 24.6 (20.5-29.6)† | 25.2 (21.4-29.5)† | 26.0 (20.9-30.9) | 5.3 (– to 8.4) | 88.8 (70.3-109.1) |
| 1 | 410 | 22.7 (19.8-25.9)† | 23.2 (20.4-26.3)† | 22.4 (17.7-28.6) | 5.0 (3.6-7.1) | 109.1 (78.8-137.7) |
| ≥2 | 388 | 18.7 (16.4-21.4)† | 18.4 (16.2-20.9)b | 18.8 (15.9-21.9) | 3.3 (– to 5.8) | 94.3 (68.4-110.5) |
| Race/ethnicity | ||||||
| Mexican American | 384 | 19.4 (17.2-21.9)† | 19.7 (17.4-22.4)† | 19.7 (16.8-22.0) | 3.3 (– to 4.7) | 81.8 (67.0-93.3) |
| Non-Hispanic White | 537 | 24.4 (21.6-27.6)‡ | 22.8 (20.4-25.7)† | 25.0 (21.7-30.0) | 4.6 (3.0-6.0) | 107.4 (79.1-113.6) |
| Non-Hispanic Black | 209 | 20.0 (16.3-24.6)† | 20.4 (16.6-24.6)† | 20.4 (12.1-26.1) | 5.6 (4.4-6.6) | 104.0 (65.7-119.7) |
| All others | 158 | 21.9 (18.2-26.4)† | 24.0 (20.4-28.2)† | 21.5 (15.8-30.0) | 5.2 (– to 8.0) | 93.2 (57.7-104.5) |
| Education | ||||||
| Less than high school | 398 | 20.7 (17.6-24.3)† | 23.8 (19.1-29.5)† | 21.3 (16.1-28.6) | 4.7 (4.6-5. 7) | 72.1 (56.7-84.4) |
| High school diploma | 284 | 20.9 (17.6-24.9)† | 21.1 (17.8-24.6)† | 21.4 (16.1-29.3) | 3.2 (– to 5.6) | 78.9 (65.2-100.7) |
| More than high school | 586 | 24.1 (21.2-27.5)† | 21.8 (19.5-24.6)† | 23.6 (20.5-28.8) | 5.0 (– to 7.6) | 109.5 (88.2 to –) |
| Family income | ||||||
| <130% of poverty income ratio | 440 | 19.9 (17.1-23.1)† | 21.7 (18.6-25.7)† | 20.6 (16.8-25.5) | 4.0 (3.1-6.2) | 68.7 (61.0-76.0) |
| ≥130% of poverty income ratio | 755 | 23.3 (20.9-25.9)† | 22.2 (20.4-24.0)† | 22.9 (20.2-27.9) | 4.7 (– to 6.4) | 107.7 (87.3-114.3) |
Unweighted n, all other analyses are weighted. “–” denotes that percentile values cannot be calculated. NHANES oversampled on pregnant women from 1999 to 2006 but discontinued started in 2007. For a reliable estimation we have combined the years 2007 to 2010 and 2015 to 2018 data together for the survey years estimation. The following exclusions apply to define healthy population: pregnant women with inflammation and liver disease. Analyses for adjusted mean take into account all the sociodemographic characteristics listed in the table (ie, the adjusted mean SF for each age group is adjusted for survey, trimester, parity, racial/ethnic group, education, and family income).
Within a group, values with different symbols (†, ‡, or §) are significantly different in means (P < .05; 2-tailed t test), and a Bonferroni adjustment was used to correct the P value for the significance test for the multiple comparisons across each sociodemographic characteristic in SF.