Maternal risk factors for low birth weight newborn in Thailand.

This multi-center unmatched case-control study was conducted at all the 5 maternal-child health care centers in Thailand by administering questionnaires by trained interviewers. Additionally Chulalongkorn Hospital Medical School and the Maharaj Hospital were also included. The entire sample of 2000 cases were recruited from all pregnant women who delivered a low birth weight (LBW) newborn weighing < 2500 gm. 4095 controls were selected from pregnant women in the same hospitals who delivered neonates weighing 2500-4000 gm. Among biological factors influencing LBW small maternal stature and weight (< 45 kg) was highly associated with LBW neonates (113 cases and 50 controls relative risk [RR] = 7.15). Maternal age of less than 18 years and 35 years and over ranked 2nd for relative risk (390 cases and 499 controls RR = 1.75). The other risk factors were parity of 1 or greater than 4 (1379 cases and 2396 controls RR = 1.68) Quetelets index of less than 20 (1696 cases and 3259 controls RR = 1.37). These were all statistically significant risk factors. An accident during the 2nd trimester (RR = 1.34) was also a risk factor. The maternal psychosocial risk factors for LBW newborns were: low family income (RR = 1.75) education (< 4 years of formal education RR = 1.35) hard work such as agricultural labor (RR = 1.46) and the need to travel (RR = 1.50) or to walk more than 2 hours to the work place (RR = 1.29). Paternal status of being a laborer an agricultural worker unemployed (RR = 1.39) or under 19 years old (RR = 1.74) were also risk factors. Pregnancy weight gain of < 10 kg had the highest degree of association with having an LBW newborn (RR = 2.21). Other risk factors were: decreased food intake during pregnancy maternal hematocrit count below 30% and interpregnancy interval of less than 12 months. Maternal obstetrical risk factors for LBW included: vaginal bleeding during early pregnancy (RR = 3.28) maternal hypertension (RR = 3.48) convulsion during pregnancy (RR = 3.29) no prenatal care or less than 4 visits maternal drug addiction (RR = 5.13) cigarette smoking (RR = 2.04) coffee or tea drinking during pregnancy and repeated induced abortions (RR = 2.16).