Which combining form means "pregnancy"?

The combining form that means "pregnancy" is "gest/o." This term derives from the Latin word “gestare,” which means "to carry" or "to bring forth." In medical terminology, "gestation" refers to the period of development in the womb from conception to birth, encompassing the entire pregnancy process.

The other combining forms have distinct meanings: "somat/o" refers to the body, "andr/o" pertains to male or masculine characteristics, and "lact/o" relates to milk or the process of lactation. Therefore, "gest/o" specifically identifies concepts and conditions associated with pregnancy, making it the correct choice in this context.