Which of the following increases significantly as pregnancy advances?

The respiratory rate is essentially unchanged, but tidal volume and resting minute ventilation increase significantly as pregnancy advances.FRC and residual volume decline due to diaphragm elevation, and significant reductions are observed by the sixth month with a progressive decline across pregnancy.Inspiratory capacity, the maximum volume that can be inhaled from FRC, increases by 5 to 10 percent or 200 to 250 mL during pregnancy. Total lung capacity --the combination of FRC and inspiratory capacity-- is unchanged or decreases by less than 5 percent at term.Ref: William&;s Obstetrics; 24th edition; Chapter 4