Which of the following is a true statement regarding a woman's bodily adaptations to pregnancy? Check all that apply.
a) Increased production of relaxin helps to relax pelvic ligaments and prepare the body for childbirth.
b) The placenta develops from the fertilized egg and provides nutrients and oxygen to the developing fetus.
c) Breast enlargement occurs due to increased production of estrogen and progesterone, preparing the breasts for lactation.
d) The amniotic sac forms to provide a protective environment for the developing fetus.