Healthy eating can be instituted at any stage of the pregnancy including nutritional adjustments, use of vitamin supplements, and smoking cessation.[1] Calcium supplementation in women who have low dietary calcium reduces the number of negative outcomes including preterm birth, pre-eclampsia, and maternal death.[93][needs update] The World Health Organization (WHO) suggests 1.5–2 g of calcium supplements daily, for pregnant women who have low levels calcium in their diet.[93] Supplemental intake of C and E vitamins have not been found to reduce preterm birth rates.[94] Different strategies are used in the administration of prenatal care, and future studies need to determine if the focus can be on screening for high-risk women, or widened support for low-risk women, or to what degree these approaches can be merged.[86] While periodontal infection has been linked with preterm birth, randomized trials have not shown that periodontal care during pregnancy reduces preterm birth rates.[86]