[Influence of stress from work and negative life events during pregnancy on different types of low birth weight]

To explore the influence of occupational stress and negative life events that occur during pregnancy on different types of low birth weight (LBW).

438 singleton LBW infants (birth weight of less than 2500 g and their pregnancy term from 28 to 42 weeks) were selected as case group, and they were further divided into symmetric LBW infants (337 cases) and asymmetric LBW infants (101 cases). According to situation of each LBW infant, a singleton with full term and normal birth weight was selected as control group matched by sex, pregnancy term, time during delivery and types of hospital. All of their mothers were inquired by well trained investigators on their socio-demographic characteristics, occupational stress, and negative life events that occurred in different pregnancy term. After controlling for mother's age, occupation, education level and family income, multinomial logistic regression was employed to asses the influence of occupational stress and negative life events on symmetric LBW and asymmetric LBW.

Compared with those using low technical skills, mothers with high technical skill utilization significantly decreased the risk of laboring both symmetric LBW (OR = 0.69, 95% CI: 0.49-0.98) and asymmetric LBW (OR = 0.53, 95% CI: 0.31-0.89). Compared with those without exposure to negative life events, mothers with negative life event score > or = 3 in the whole duration of pregnancy had significantly increased the risk of delivering symmetric LBW (OR = 2.30, 95% CI: 1.08-4.88), mothers with negative life event score > or = 3 in the middle three months of pregnancy, > or = 3 in the last three months of pregnancy, = 2 and > or = 3 in the whole duration of pregnancy had significantly increased the risk of delivering asymmetric LBW, and their OR (95% CI) was 8.85 (1.97-39.68), 3.80 (1.40-10.29), 3.58 (1.33-9.66) and 3.48 (1.32-9.13), respectively.

Occupational stress and negative life events might produce different influence on symmetric LBW and negative life events that occur in the different terms of pregnancy had different impact on symmetric LBW and asymmetric LBW.