Answer:
Option D
Step-by-step explanation:
"Premature birth" or option D is when the mother who is carrying the child goes into labor earlier than her due date. Which is a major complication for childbirth and is even pretty dangerous for the child itself. The reason why premature birth is a major complication it's because if the child isn't fully developed then it may not be able to live without the mother, which is very dangerous for the baby. It's not option A because a pap smear is a screening test, it's not option B because blastocyst has nothing to do with the birth of a child, and it's also not option C because an ultrasound is another type of test while the mother is still pregnant with the child.
Hope this helps.