Generate text that best answers this question: prenatal vitamins
Non-anaemic pregnant women should not take iron supplements.
(1) Iron-deficiency anaemia during pregnancy increases the risk of low birth weight and preterm birth; (2) In a randomised double-blind placebo-controlled trial, iron supplementation in pregnant women with haemoglobin levels of at least 13.2 g/100 ml at the beginning of the 2nd trimester was associated with low birth weight and maternal hypertension; (3) In a trial in women with haemoglobin levels of at least 11.5 g/100 ml who took supplemental iron, haemoglobin levels above 14.5 g/100 ml at 28 weeks of gestation were associated with an 8-fold increase in the risk of preterm birth and a 6-fold increase in the risk of low birth weight; (4) An epidemiological study showed a link between high maternal haemoglobin levels and low birth weight; (5) In practice, iron supplements should not be taken by pregnant women whose haemoglobin levels exceed 11 g/100 ml during the 1st and 3rd trimesters and 10.5 g/100 ml during the 2nd trimester.