A 17 year old primigravida asks you what to expect during her pregnancy. You tell her that normally during pregnancy:

During pregnancy many physiological changes take place in a mother's body. Maternal blood volume increases up to 40% due to elevated testosterone and estrogen levels. Bone marrow production of erythrocytes also increases, but does not keep up with the plasma volume expansion, resulting in a decrease in hematocrit (physiological anemia of pregnancy). Respiratory minute volume increases by about 50% because of the increased basal metabolic rate and oxygen consumption. This increase is largely due to an increase in tidal volume without increase in respiratory rate. Residual volume and expiratory reserve volume decreases. Gastrointestinal tone and motility decrease because of the inhibitory effect of progesterone on these smooth muscles. Ref: Alford C., Nurudeen S. (2013). Chapter 4. Physiology of Reproduction in Women. In A.H. DeCherney, L. Nathan, N. Laufer, A.S. Roman (Eds), CURRENT Diagnosis & Treatment: Obstetrics & Gynecology, 11e.