Table 2.
Mean Z-score [standard deviation] for fetal biometric measurements at approximately 18 weeks of gestation according to maternal and fetal characteristics
| Head measures | Body measures | |||||
|---|---|---|---|---|---|---|
| Variable | n (%) | Estimated fetal weight | Head circumference | Biparietal diameter | Abdominal circumference | Femur length |
| Maternal characteristics | ||||||
| Age at study enrollment | * | ** | * | |||
| <30 years | 83 (37.2) | 0.21 [1.46] | -0.12 [0.82] | -1.19 [1.07] | -0.30 [0.79] | -0.13 [0.85] |
| ≥30 years | 140 (62.8) | 0.45 [1.46] | 0.15 [0.78] | -0.75 [0.92] | -0.29 [0.83] | 0.12 [0.80] |
| Pre-pregnancy BMI, kg/m2 | ||||||
| <25.0, normal | 111 (49.8) | 0.51 [1.48] | 0.13 [0.81] | -0.78 [1.08] | -0.19 [0.82] | 0.06 [0.82] |
| ≥25.0 to < 30.0, overweight | 51 (22.9) | 0.41 [1.59] | 0.10 [0.90] | -0.96 [0.96] | -0.28 [0.84] | 0.64 [0.84] |
| ≥30.0, obese | 37 (16.6) | -0.06 [1.20] | -0.22 [0.66] | -1.18 [0.85] | -0.49 [0.79] | -0.14 [0.70] |
| unknown | 24 (10.8) | 0.21 [1.42] | -0.03 [0.73] | -1.04 [0.86] | -0.48 [0.76] | 0.08 [1.02] |
| Smoking during pregnancy | ||||||
| non-smoker | 181 (81.2) | 0.36 [1.49] | 0.05 [0.82] | -0.90 [1.04] | -0.29 [0.84] | 0.04 [0.80] |
| smoker | 19 (8.5) | 0.41 [1.28] | 0.03 [0.74] | -0.96 [0.74] | -0.10 [0.58] | -0.18 [1.00] |
| unknown | 23 (10.3) | 0.28 [1.41] | 0.06 [0.75] | -1.00 [0.89] | -0.45 [0.78] | 0.13 [0.92] |
| Parity | ** | |||||
| First live birth | 82 (36.8) | 0.46 [1.30] | 0.14 [0.79] | -0.62 [0.90] | -0.21 [0.71] | 0.05 [0.83] |
| 1 or more live births | 136 (61.0) | 0.28 [1.54] | -0.01 [0.81] | -1.09 [0.99] | -0.35 [0.86] | 0.01 [0.82] |
| unknown | 5 (2.2) | 0.83 [1.95] | 0.23 [0.94] | -1.01 [1.85] | -0.02 [1.17] | 0.23 [1.06] |
| Urinary total arsenic | ||||||
| below the median | 112 (50.2) | 0.28 [1.40] | 0.07 [0.76] | -0.88 [0.90] | -0.33 [0.83] | -0.04 [0.77] |
| above the median | 111 (49.8) | 0.44 [1.52] | 0.86 [0.86] | -0.95 [1.09] | -0.26 [0.80] | 0.09 [0.88] |
| Fetal characteristics | ||||||
| Sex | * | ** | * | |||
| male | 114 (51.1) | 0.51 [1.35] | 0.20 [0.76] | -0.69 [0.95] | -0.16 [0.76] | 0.02 [0.80] |
| female | 101 (45.3) | 0.23 [1.53] | -0.10 [0.82] | -1.13 [0.98] | -0.43 [0.84] | 0.07 [0.82] |
| unknown | 8 (3.6) | -0.19 [1.91] | -0.27 [0.91] | -1.49 [1.30] | -0.43 [1.07] | -0.38 [1.23] |
Abbreviations: SD, standard deviation; BMI, body mass index.
ANOVA (analysis of variance) used to compare means across categories.
*p-value < 0.05, **p-value < 0.01.