13, AMNIOTIC, APPROXIMATELY, CORD, CZLOWIEK, DEVELOPMENT, EMBRION, EMBRYO, FETAL, FETUS, GESTATION, HUMAN, LEK, LEKARSTWO, MEDICAL, MEDICINE, MEDYCYNA, MEDYCZNA, MEDYCZNE, MEDYCZNY, NAUKA, OLD, OMIKRON, PEPEK, PLOD, PROGRES, REPRODUCTION, REPRODUCTIVE, ROZWOJ, SAC, SCIENCE, SCIENTIFIC, STARA, STARE, STARY, SYSTEM, SZNUR, SZNUREK, TRIMESTER, UMBILICAL, WEEK, WEEKS, XIII, YOLK, ZOLTKO,