embryonic period 3-8 weeks 3周 4周 5周 6周 7周 8周 fetal period: after 9 weeks perinatal stage: 26 weeks to birth 9周16周 36)(38周 Teratology: abnormal development of fetusembryonic period: 3-8 weeks fetal period: after 9 weeks *perinatal stage: 26 weeks to birth *Teratology: abnormal development of fetus