先天性障碍，又称「先天性疾病」、「天生缺陷」，是指发育中的胎儿因为遗传性疾病或发育环境等因素导致某个部位特征结构畸形，有些疾病可以透过产前诊断（筛检）被检测到。天生缺陷包括感染、双亲的基因遗传、染色体变异等，而这些混乱结果取决于外在环境的影响所产生的。根据动物的研究，发育中的胎儿所得到的营养取决于父母的进食，也有可能对胎儿出生以后长期影响到他的生活型态。然而也透过动物的研究指出，父母的思维、生活作息也会影响到胎儿的发育过程，由实验可知，父亲如果整天酗酒、少吃蔬果类的食物、吸烟、吸毒品等不良行为，更让胎儿造成基因突变而导致先天性障碍。 大约有3%的幼儿有先天性障碍，从1990年至2013年期间数据统计显示：每年因先天性疾病导致死亡者从751,000人降至632,000人。

Congenital disorder, also known as congenital disease, birth defect or anomaly, is a condition existing at or before birth regardless of cause. Of these diseases, those characterized by structural deformities are termed "congenital anomalies" and involve defects in a developing fetus. Birth defects vary widely in cause and symptoms. Any substance that causes birth defects is known as a teratogen. Some disorders can be detected before birth through prenatal diagnosis (screening).