Developmental toxicants are agents that cause adverse effects on the developing child. Effects can include birth defects, low birth weight, biological dysfunctions, or psychological or behavioral deficits that become manifest as the child grows. Maternal exposure to toxic chemicals during pregnancy can disrupt the development or even cause the death of the fetus. Exposure of pregnant women to mercury, lowers birth weight and can cause severe brain damage in children. While developmental toxicity usually results from prenatal exposures to toxicants experienced by the mother, it can also result from paternal exposures. For example, the occupational exposure of men to vinyl chloride has been associated with increased rates of spontaneous abortion in their wives. Early postnatal contact with toxicants can also affect normal development. Exposure to secondhand tobacco smoke, for example, increases an infant's risk of contracting respiratory infections or succumbing to sudden infant death syndrome.