The most likely reason for aching legs during pregnancy is sluggish circulation through the veins. One of the (many!) side effects of the hormones of pregnancy is the relaxation of smooth muscle fibres, including the smooth muscle fibres in the wall of blood vessels. This means that the venous circulation tends to be less efficient than at other times, leading to problems such as swollen ankles, varicose veins, haemorrhoids, and aching legs. Legs tend to suffer the most when you have been standing or sitting still for some time (due to the effects of gravity and relative immobility), and in later pregnancy (because the weight of the uterus further constricts the circulation).
The following may help relieve the aching. Firstly, movement. If you are forced by work or other circumstances to stand for long periods, boost your circulation by exercising your calf muscles. Rise up and down on tiptoes. Circle your ankles. Flex your ankles up and down. Secondly, wearing support tights. Not ideal perhaps in summer, but a godsend at other times! Finally, proponents of herbal medicine suggest that eating onions and raw garlic may help to boost the circulation. Fresh parsley is also reputed to help – and nettles. Take your pick!
Aching legs are very common in pregnancy – a nuisance, but not abnormal. Danger signs relating to the circulation include swelling of one leg, tenderness and/or redness over one calf, pain on walking or moving the leg, sudden breathlessness or chest or high back pain, and sudden unbearable headache. All of these symptoms may arise from a thrombosis (or blood clot) and/or embolism (clot travelling around the body). Although relatively uncommon, these conditions are both more likely to occur during pregnancy than at other times, so if you develop any of these symptoms, contact your midwife, GP, or hospital clinic or labour ward as a matter of urgency.