Gynaecology & Obstetrics General 05dc07f1 All are true regarding fetal skeletal mineralization except A Approximately 30g of calcium is needed especially during 3rd trimester. B Calcium required by fetus is only 10 % of maternal, skeletal calcium. C Amount of calcium absorbed increases to 400mg / day in the third trimester. D PTH plasma concentration is decreased in first trimester, but increases progressively later. High-Yield Explanation Fetal calcium requirement is only 3 % of total calcium held within maternal skeleton.