Table 2.
Characteristics of study participants, stratified by analysis
| Characteristic | N (%) or mean ± standard deviation | ||
|---|---|---|---|
|
| |||
| Included in analyses of prenatal PFASs and early childhood cognition (n=986) | Included in analyses of prenatal PFASs and mid-childhood cognition (n=865) | Included in analyses of childhood PFASs and mid-childhood cognition (n=642) | |
| Early childhood cognitive assessments | |||
| Peabody Picture Vocabulary Test (PPVT-III)a (n=948) | 104.4 ± 14.1 | - | - |
| Wide Range Assessment of Visual Motor Abilities (WRAVMA) Composite Scorea (n=919) | 102.1 ± 11.5 | - | - |
| WRAVMA Visual-Motor (a (n=971) | 99.0 ± 11.3 | - | - |
| WRAVMA Fine Motora (n=968) | 98.0 ± 10.8 | - | - |
| WRAVMA Visual-Spatiala (n=937) | 108.1 ± 13.8 | - | - |
| Mid-childhood cognitive assessments | |||
| Kaufman Brief Intelligence Test (KBIT-2) Verbal IQa (n=851 with prenatal PFASs, 631 with child PFASs) | - | 112.1 ± 14.9 | 111.1 ± 15.4 |
| KBIT-2 Non-Verbal IQa (n=862 with prenatal PFASs, 640 with child PFASs) | - | 106.5 ± 16.9 | 105.8 ± 16.9 |
| WRAVMA Visual-Motor a (n=853 with prenatal PFASs, 635 with child PFASs) | - | 92.1 ± 16.7 | 93.1 ± 17.2 |
| Visual Memory Index of the Wide Range Assessment of Memory and Learning (WRAML2) Design Memory (WRAML2)b (n=853 with prenatal PFASs, 636 with child PFASs) | - | 8.0 ± 2.8 | 8.1 ± 2.7 |
| WRAML 2 Picture Memoryb (n=855 with prenatal PFASs, 635 with child PFASs) | - | 8.9 ± 3.0 | 9.0 ± 3.0 |
| Maternal characteristics | |||
| Year of enrollment | |||
| 1999 | 245 (25) | 212 (25) | - |
| 2000 | 362 (37) | 329 (38) | - |
| 2001 | 343 (35) | 289 (33) | - |
| 2002 | 36 (4) | 35 (4) | - |
| Age at enrollment (years) | 32.4 ± 5.1 | 32.1 ± 5.3 | 31.8 ± 5.6 |
| Parity at enrollment | |||
| Nulliparous | 468 (47) | 415 (48) | 271 (42) |
| Parous | 518 (53) | 450 (52) | 371 (58) |
| Proxy for breastfeeding of a prior childc | |||
| Nulliparous (assume no prior breastfeeding) | 468 (47) | 415 (48) | 271 (42) |
| Parous, did not breastfeed Project Viva child | 100 (10) | 76 (9) | 57 (9) |
| Parous, breastfed Project Viva child | 391 (40) | 343 (40) | 283 (44) |
| Missing data | 27 (3) | 31 (4) | 31 (5) |
| Education (at enrollment) | |||
| Less than college degree | 286 (29) | 275 (32) | 225 (35) |
| College degree | 378 (38) | 300 (35) | 230 (36) |
| Graduate degree | 320 (32) | 286 (33) | 183 (29) |
| Missing data | 2 (<1) | 4 (1) | 4 (1) |
| Race/ethnicity | |||
| White | 722 (73) | 594 (69) | 397 (62) |
| Black | 115 (12) | 129 (15) | 133 (21) |
| Asian | 40 (4) | 39 (5) | 29 (5) |
| Hispanic | 60 (6) | 59 (7) | 46 (7) |
| Other | 47 (5) | 40 (5) | 33 (5) |
| Missing data | 2 (<1) | 4 (<1) | 4 (1) |
| Smoking in pregnancy | |||
| Smoked in pregnancy | 110 (11) | 166 (19) | 73 (11) |
| Former smoker | 206 (21) | 88 (10) | 122 (19) |
| Never smoker | 666 (68) | 608 (71) | 446 (70) |
| Missing data | 4 (<1) | 3 (<1) | 1 (<1) |
| Pre-pregnancy body mass index (kg/m2) | 24.8 ± 5.3 | 24.8 ± 5.3 | 25.0 ± 5.3 |
| Missing data | 2 (<1) | 6 (1) | 4 (1) |
| Gestational duration at time of pregnancy blood draw (weeks) | 9.6 ± 2.2 | 10.1 ± 2.3 | - |
| Estimated glomerular filtration rate at time of pregnancy blood draw (mL/min per 1.73 m2) | 110.5 ± 49.5 | 109.4 ± 38.5 | - |
| Missing data | 7 (<1) | 13 (2) | - |
| Plasma albumin at time of pregnancy blood draw (g/dL) | 8.3 ± 2.8 | 8.2 ± 2.0 | - |
| Missing data | 46 (5) | 44 (5) | - |
| PPVT-III score at early childhood cognitive assessment | 106.1 ± 14.6 | - | - |
| Missing data | 23 (2) | - | - |
| IQ (KBIT-2 composite) at mid-childhood cognitive assessment | - | 106.9 ± 15.2 | 105.1 ± 15.6 |
| Missing data | - | 15 (2) | 13 (2) |
| Paternal characteristics | |||
| Education (at enrollment) | |||
| Less than college degree | 287 (29) | 251 (29) | 199 (31) |
| College degree | 332 (34) | 284 (33) | 199 (31) |
| Graduate degree | 281 (28) | 241 (28) | 168 (26) |
| Missing data | 86 (9) | 89 (10) | 76 (12) |
| Child characteristics | |||
| Sex | |||
| Female | 471 (48) | 419 (48) | 305 (48) |
| Male | 515 (52) | 446 (52) | 337 (52) |
| Duration of breastfeeding (months up to 12) | 6.3 ± 4.5 | 6.5 ± 4.6 | 6.4 ± 4.5 |
| Missing data | 51 (5) | 58 (7) | 52 (8) |
| Age at early childhood assessment (years) | 3.3 ± 0.4 | - | - |
| Age at mid-childhood assessment (years) | - | 8.0 ± 0.9 | 7.9 ± 0.8 |
| Year of mid-childhood blood draw | |||
| 2007 | - | - | 67 (10) |
| 2008 | - | - | 220 (34) |
| 2009 | - | - | 206 (32) |
| 2010 | - | - | 149 (23) |
| Household characteristics | |||
| HOME-SF scored at mid-childhood assessment | - | 18.4 ± 2.2 | 18.2 ± 2.3 |
| Missing data | - | 26 (3) | 13 (2) |
| Household annual income at enrollment | |||
| ≤$40 K | 115 (12) | - | - |
| >$40–≤$70 K | 217 (22) | - | - |
| >$70 K | 591 (60) | - | - |
| Missing data | 63 (6) | - | - |
| Household annual income at mid-childhood | |||
| ≤$40 K | - | 99 (11) | 90 (14) |
| >$40–≤$70 K | - | 110 (13) | 96 (15) |
| >$70–≤$150 K | - | 367 (42) | 272 (42) |
| >$150 K | - | 234 (27) | 148 (23) |
| Missing data | - | 55 (6) | 36 (6) |
a
PPVT-III, WRAVMA and KBIT-2 scores standardized to mean=100, SD=15.
b
WRAML2 scores standardized to mean=10, SD=3.
c
Estimated using maternal parity and breastfeeding data for the Project Viva child.
d
Home Observation for Measurement of the Environment (Short Form); scale: 0–22, with higher scores representing better support for cognitive development in home.