Association of a lack of psychosocial resources and the risk of giving birth to small for gestational age infants: a stress hypothesis

Objective: To test the stress hypothesis that women who give birth to small for gestational age infants lack important psychosocial coping resources, such as a sufficient social network, social support and control in daily li fe. Design: A prospective cohort study of nulliparous pregnant women. Setting: Antenatal care units in the city of Malmo, Sweden. Population: All women (n = 994) during a one year period (1991-1992) were i nvited, and 872 (87.7%) participated. This study was restricted to pregnanc ies resulting in singleton live birth (n = 826); 6.7% of infants were class ified as small for their gestational age. Methods: Self-administered questionnaires were given to all women at the ti me of their first antenatal visit. Main outcome measures: The classification of small for gestational age was based on a gender-specific intrauterine growth reference curve. Newborn bab ies were classified as being small for gestational age if their birthweight was > 2 SD below the mean weight for gestational age. Results: Lack of psychosocial resources, such as social stability, social p articipation, emotional and instrumental support, all increased the Likelih ood of delivering an infant that was small for gestational age. The odds ra tios when controlled for demographic background factors, lifestyle factors and anthropomorphic measures were: OR 1.7 (95% CI 0.9-3.3) for women with p oor social stability; OR 2.2 (95% CI 1.1-4.4) for women with poor social pa rticipation; OR 2.6 (95% CI 1.2-5.7) for women with poor instrumental suppo rt; and OR 1.5 (95% CI 0.8-2.8) for women with poor emotional support. Simu ltaneous exposure to a poor total network index, as well as a poor total su pport index showed a significantly increased odds ratio for having a small for gestational age baby: OR 3.3 (95% CI 1.6-6.7) and OR 2.7 (95% CI 1.3-5. 6), respectively. A synergy index of 9.0 and 6.8 supported the assumption o f an interaction between immigrant status and poor total network or poor to tal support, in a synergistic direction. Conclusions: The findings support the stress-hypothesis that a lack of psyc hosocial resources might increase the risk of giving birth to a baby that i s small for gestational age.