Abstract. Abortion is defined as a threat or release of the results of conception before the fetus can live outside the womb. As a limitation is a pregnancy less than 20 weeks or a fetus weighing less than 500 grams. Abortion in Indonesia based on the results of Riskesdas 2010 was reported as much as 4% in women of reproductive age. A study states that the frequency of spontaneous abortion in Indonesia is 10-15% of 6 million pregnancies each year. Several studies have been conducted to determine the relationship between body mass index (BMI) and the risk of spontaneous abortion.The research method used in this study was a descriptive study with a cross-sectional study design with research subjects using secondary data in the form of medical records of pregnant women patients who experienced spontaneous abortion at Hasan Sadikin Hospital in Bandung, West Java, 2016-2017 period. The data obtained were analyzed using univariable and bivariable analysis. In this study the body mass index results was obtained in terms of mean and median showed a significant difference (p <0.05) between the case group and the control group. For the age, parity, education, and occupation of mothers between the two study groups were not significant (p> 0.05); while the nutritional status of pregnant women showed a significant difference (p <0.05). In this study, the results show that pregnant women with underweight nutritional status were 2.34 times at risk than pregnant women with normal nutritional status. From the results of this study it can be concluded there was a relationship between BMI and spontaneous abortion incidences. Underweight nutritional status were 2.34 times at risk than pregnant women with normal nutritional status.Keywords: Spontaneous Abortion, BMI, Nutritional Status, UnderweightAbstrak.  Abortus didefinisikan sebagai ancaman atau pengeluaran hasil konsepsi kurang dari 20 minggu atau berat janin kurang dari 500 gram. Kejadian abortus di Indonesia berdasarkan hasil Riskesdas 2010 dilaporkan sebanyak 4% pada wanita usia reproduksi. Sebuah penelitian menyebutkan bahwa frekuensi abortus spontan di Indonesia adalah 10-15% dari 6 juta kehamilan setiap tahunnya. Beberapa penelitian telah dilakukan untuk mengetahui hubungan antara indeks massa tubuh (IMT) dengan risiko terjadinya abortus spontan. Metode penelitian yang digunakan dalam penelitian ini adalah penelitian deskriptif dengan rancangan penelitian cross-sectional dengan subjek penelitian rekam medis pasien ibu hamil yang mengalami abortus spontan di Rumah Sakit Hasan Sadikin Bandung, Jawa Barat periode 2016-2017. Data yang didapatkan dianalisis menggunakan analisis univariabel dan bivariabel. Pada penelitian ini didapatkan hasil indeks massa tubuh dari segi rata-rata dan median menunjukkan ada perbedaan yang bermakna (p<0,05) antara kelompok kasus dan kelompok kontrol. Untuk kelompok usia, paritas, pendidikan, dan pekerjaan ibu antara kedua kelompok penelitian tidak bermakna (p>0,05); sedangkan status gizi ibu hamil menunjukkan ada perbedaan yang bermakna (p<0,05). Pada penelitian ini didapatkan hasil bahwa ibu hamil dengan status gizi underweight berisiko 2,34 kali lebih besar dibandingkan dengan ibu hamil dengan status gizi normal. Dari hasil penelitian ini dapat ditarik kesimpulan terdapat hubungan antara IMT dengan kejadian abortus spontan, status gizi underweight berisiko 2,34 kali lebih besar dibandingkan ibu hamil dengan status gizi normal terhadap kejadian abortus spontan. Kata Kunci: Abortus Spontan, IMT, Status Gizi, Underweight