<![CDATA[Babies born weighing <2,500 grams are called LBW, the risk of causing death is 20 times higher than normal birth weight babies. Maternal factors, pregnancy factors, fetal factors, placental factors, and environmental factors are risk factors for LBW. The purpose of the study was to determine the dominant factor causing the occurrence of LBW in the perinatology room of RSUD Dr. Pirngadi Medan. This research is descriptive with a cross sectional approach. The population, namely mothers who gave birth to LBW as many as 117 people from January-December 2020, a sample of 32 respondents was taken by consecutive sampling. The results showed that the risk factors for the incidence of LBW were 46.9% age <20 years, history of anemia 34.4% and hypertension 25%, pyrimiparous mother (40.6%) and grande multipara (34.4%). family with income > Rp. 1-5 million/month as many as 53.1%, mothers without drinking alcohol and smoking habits as much as 84.4%, mothers experiencing antepartum bleeding as much as 65.6%, maternal intervals <1 and 1 year each 50.0 %, maternal gestational age <37 weeks as much as 53.1%, not gemelli as much as 78.1%, not exposed to infection 100%, premature rupture of membranes as much as 53.1%), no hydramion, living in highland areas as much as 81 ,2%. It was concluded that the highest risk factors for the incidence of LBW were maternal age at pregnancy <20 years, mothers with a history of anemia and hypertension, primiparas, antepartum bleeding and pregnancy <37 weeks. It is recommended that adolescents maintain their health, especially their reproductive health and delay the age of marriage until the age of 20 years to reduce the risk of low birth weight. ABSTRAKBerat bayi lahir <2.500 gram disebut BBLR, beresiko menyebabkan kematian 20 kali lebih tinggi dibanding bayi berat lahir normal. Faktor ibu, faktor kehamilan, faktor janin, faktor plasenta, dan faktor lingkungan merupakan faktor resiko terjadinya BBLR. Tujuan penelitian mengetahui faktor dominan penyebab terjadinya BBLR di ruang perinatologi RSUD Dr. Pirngadi Medan. Penelitian bersifat deskriptif dengan pendekatan cross sectional. Populasi yaitu ibu yang melahirkan BBLR sebanyak 117 orang dari bulan Januari-Desember 2020, sampel sebanyak 32 responden diambil secara consecutive sampling. Hasil penelitian menunjukkan faktor resiko terhadap kejadian BBLR adalah faktor umur <20 tahun sebesar 46,9%, riwayat penyakit anemia 34,4% dan hipertensi 25%, ibu pirimipara (40,6 %) dan grande multipara (34,4%), keluarga dengan penghasilan >Rp. 1-5 juta/bulan sebanyak 53,1%, ibu tanpa kebiasaan minum alkohol dan merokok sebanyak 84,4%, ibu mengalami perdarahan antepartum sebanyak 65,6%, jarak kehamilan ibu <1 dan ?1 tahun masing-masing 50,0%, usia kehamilan ibu <37 minggu sebanyak 53,1%, tidak gemelli sebanyak 78,1%, tidak terkena infeksi 100%, ketuban pecah dini sebanyak 53,1%), tidak ada hidramion, bertempat tinggal di daerah dataran tinggi sebanyak 81,2%. Disimpulkan bahwa faktor resiko tertinggi penyebab kejadian BBLR yaitu usia ibu saat hamil <20 tahun, ibu memiliki riwayat penyakit anemia dan hipertensi, primípara, perdarahan antepartum dan kehamilan <37 minggu. Disarankan agar remaja memelihara kesehatan terutama kesehatan reproduksinya dan menunda usia pernikahan sampai usia ?20 tahun untuk menurunkan resiko terjadinya BBLR.]]>
