Fetal is the usual American spelling of foetal. It means “of a fetus”: a baby still growing inside the mother, before birth. You meet it in medical and science talk — fetal development, a fetal heartbeat, fetal alcohol syndrome — and it sounds clinical, not cuddly. Doctors and textbooks use it; it is not a word for baby talk. British English has long written foetal and foetus with oe. American English writes fetal and fetus. Though actually, fetus / fetal is now common even in a lot of British scientific writing, so the old school-book split is tidier than the page in front of you. Keep the pair together: fetus goes with fetal; foetus goes with foetal.