Table 3

Associations between maternal occupational exposure to physically demanding work during pregnancy and fetal growth measured by ultrasound second and third trimester analyses

Physically demanding workNHead circumference (mm) 20 weeksNHead circumference (mm) 30 weeks
Crude*AdjustedCrude*Adjusted
Long period of standing40654152
 No2344ReferenceReference2385ReferenceReference
 Occasionally876−0.11 (−0.47 to 0.45)0.16 (−0.30 to 0.61)906−1.17 (−1.84 to −0.49)−0.80 (−1.46 to −0.14)
 Often845−0.24 (−0.71 to 0.23)0.05 (−0.44 to 0.54)861−1.36 (−2.06 to −0.67)−0.72 (−1.43 to −0.01)
Lifting >25 kg40994184
 No3822ReferenceReference3900ReferenceReference
 Occasionally2090.70 (−0.12 to 1.52)0.66 (−0.15 to 1.47)2140.01 (−1.20 to 1.23)−0.13 (−1.30 to 1.04)
 Often68−0.58 (−2.03 to 0.87)−0.30 (−1.73 to 1.13)70−1.61 (−3.75 to 0.53)−0.96 (−3.02 to 1.10)
Work hours40114094
 1–24 h/week1020ReferenceReference1051ReferenceReference
 25–39 h/week2002−0.03 (−0.47 to 0.41)−0.11 (−0.56 to 0.34)2027−0.32 (−0.97 to 0.33)−0.32 (−0.97 to 0.33)
 >40 h/week9890.03 (−0.48 to 0.55)−0.13 (−0.69 to 0.44)1016−0.03 (−0.79 to 0.73)−0.07 (−0.88 to 0.75)
Physically demanding workNAbdominal circumference (mm) 20 weeksNAbdominal circumference (mm) 30 weeks
Crude*AdjustedCrude*Adjusted
Long period of standing40804179
 No2354ReferenceReference2402ReferenceReference
 Occasionally879−0.57 (−1.18 to 0.03)−0.37 (−0.98 to 0.24)907−0.95 (−1.91 to 0.01)−0.59 (−1.55 to 0.37)
 Often847−0.31 (−0.93 to 0.31)−0.03 (−0.69 to 0.63)870−0.71 (−1.70 to 0.28)0.02 (−1.02 to 1.06)
Lifting >25 kg41144212
 No3837ReferenceReference3928ReferenceReference
 Occasionally2090.37 (−0.72 to 1.45)0.27 (−0.82 to 1.35)214−0.13 (−1.85 to 1.60)−0.31 (−2.02 to 1.40)
 Often68−0.16 (−2.08 to 1.76)0.02 (−1.89 to 1.93)70−0.01 (−3.06 to 3.04)0.23 (−2.77 to 3.23)
Work hours40274120
 1–24 h/week1024ReferenceReference1057ReferenceReference
 25–39 h/week2011−0.31 (−0.89 to 0.26)−0.26 (−0.86 to 0.35)2038−1.08 (−2.00 to −0.16)−0.57 (−1.52 to 0.38)
 >40 h/week992−0.67 (−1.36 to 0.01)−0.57 (−1.33 to 0.18)1025−1.34 (−2.42 to −0.26)−0.51 (−1.70 to 0.68)
Physically demanding workNEstimated fetal weight (g) 20 weeksNEstimated fetal weight (g) 30 weeks
Crude*AdjustedCrude*Adjusted
Long period of standing40634172
 No2343ReferenceReference2398ReferenceReference
 Occasionally876−0.65 (−3.86 to 2.57)−0.41 (−3.68 to 2.85)906−13.06 (−26.70 to 0.63)−7.56 (−21.23 to 6.12)
 Often8440.21 (−3.10 to 3.52)0.04 (−3.49 to 3.56)868−6.42 (−20.52 to 7.67)2.47 (−12.38 to 17.31)
Lifting >25 kg40964205
 No3821ReferenceReference3923ReferenceReference
 Occasionally2075.41 (−0.38 to 11.21)4.10 (−1.71 to 9.91)2126.24 (−18.52 to 31.01)1.50 (−22.96 to 25.96)
 Often682.01 (−8.20 to 12.22)1.23 (−8.99 to 11.45)709.74 (−33.76 to 53.24)12.32 (−30.52 to 55.17)
Work hours40094113
 1–24 h/week1019ReferenceReference1055ReferenceReference
 25–39 h/week20020.05 (−3.03 to 3.13)1.65 (−1.59 to 4.89)2034−15.35 (−28.47 to −2.24)−5.69 (−19.23 to 7.84)
 >40 h/week988−2.78 (−6.41 to 0.85)0.02 (−4.02 to 4.06)1024−19.52 (−34.93 to −4.10)−3.84 (−20.72 to 13.05)
  • Figures in bold represent a statistically significant decrease in measures of fetal growth.

  • * Adjusted for gestational age at ultrasound.

  • Adjusted for gestational age at ultrasound, maternal age, height at intake, weight before pregnancy, educational level, ethnicity, parity, smoking, alcohol use, folic acid supplement use, self-perceived health and fetal gender.