showing a diminishing effect of low GWG with increasing BMI. In the highest GWG group, the relative risks for neonatal mortality for underweight, normal weight, overweight, and obese women were 1.0, 1.2, 1.4, and 1.8, respectively, showing the exact opposite tendency—excessive GWG was more strongly associated with neonatal death with increasing prepregnancy BMI. Maternal age at delivery did not affect neonatal mortality. After adjusting for gestational age at delivery, no association was found between teenage pregnancy and neonatal mortality. The same general pattern was seen for postneonatal deaths but was less pronounced (see Table 6-1).

More studies of infant mortality are needed, but the evidence from Chen et al. (2009) warrants serious consideration not only because of the

TABLE 6-1 Maternal Prepregnancy BMI and Gestational Weight Gain of Infant Deaths and Controls (1988 National Maternal and Infant Health

Survey [NMIHS]) Maternal Prepregnancy BMI (kg/m2)

Total Weight Gain During Pregnancya (kg)

Neonatal Death ORb (95% CI)

Postneonatal Death ORb (95% CI)

Infant Death ORb (95% CI)

< 18.5

< 6.0

3.55 (1.92-6.54)

2.96 (1.42-6.15)

3.26 (1.86-5.72)

 

6.0-11.6

1.35 (0.88-2.06)

1.34 (0.83-2.14)

1.34 (0.93-1.92)

 

12.0-17.6c

1.00

1.00

1.00

 

≥ 18.0

0.99 (0.63-1.54)

0.55 (0.32-0.95)

0.79 (0.53-1.17)

18.5-24.9

< 6.0

3.07 (2.45-3.85)

1.96 (1.51-2.55)

2.58 (2.12-3.14)

 

6.0-11.6

1.41 (1.19-1.68)

1.12 (0.92-1.36)

1.29 (1.11-1.49)

 

12.0-17.6c

1.00

1.00

1.00

 

≥ 18.0

1.15 (0.96-1.37)

0.94 (0.77-1.15)

1.06 (0.91-1.23)

25-29.9

< 6.0

1.98 (1.34-2.92)

0.81 (0.51-1.29)

1.42 (1.02-1.99)

 

6.0-11.6

1.20 (0.85-1.68)

0.64 (0.43-0.95)

0.94 (0.71-1.25)

 

12.0-17.6c

1.00

1.00

1.00

 

≥ 18.0

1.41 (1.00-2.00)

0.87 (0.58-1.31)

1.16 (0.87-1.56)

≥ 30

< 6.0

1.19 (0.69-2.06)

0.81 (0.40-1.62)

1.04 (0.64-1.70)

 

6.0-11.6

0.67 (0.39-1.17)

0.91 (0.47-1.78)

0.78 (0.48-1.26)

 

12.0-17.6c

1.00

1.00

1.00

 

≥ 18.0

1.78 (0.96-3.33)

1.29 (0.58-2.84)

1.61 (0.92-2.81)

NOTE: Midpoint and range values for outcomes (neonatal death, postnatal death, infant death) are derived using a separate reference group for each BMI category.

aWeight gain during pregnancy projected to 40 weeks’ gestation.

bAdjusted for race, maternal age at pregnancy, maternal education, maternal smoking during pregnancy, child’s sex, live birth order, and plurality.

cReferent group for comparisons within BMI stratum.

SOURCE: Modified from Chen et al., 2009.



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