Oestrogen: stimulates the growth of the uterus and breasts, and high level of oestrogen can result in excess water retention, nausea (specially in the first trimester) and joint looseness.
Progestrone: Thickens and develops the walls of the uterus, controlling and relaxing to stop contracting excessively.
Relaxin: Softens ligaments, cartilage and the cervix, allowing these tissues to spread during deliver. This is a major area you should be careful whilst doing stretching exercises.
Insulin: resistance increases during pregnancy, this make the pregnant women’s pattern of energy utilization similar to that of a mild diabetic. In mid and late pregnancy insulin resistance serves to utilize more fat for maternal energy and rest during exercise.