Backgorund: Infant mortality rate is an indicator of health development written in the Social Medium-Term Development Plan of 2015-2019. One of the reasons behind the high infant mortality rate is low birth weight. Smoke exposure on the pregnant mother might be the trigger. Smokes from cigarettes contain free radicals that may cause disorders to the fetus growth. Purpose: To prove the effect of the ethanol extract of Manalagi Apple peel in various dosages to prevent weight loss on baby rat born from pregnant rat that is exposed to smoke. Method: This research used Randomized Post Test Only Control Group Design by comparing the weight of newborn baby rats from 5 groups. There were 5 pregnant rats in each group. K-was a group with no administration of apple peel's ethanol extract and no exposure to smoke, while K+ was a group that was exposed to smoke and not administered with ethanol extract of apple peel. Group P1 (7 mg/ Kg BB), P2 (14 mg/Kg BB), P3 (28 mg/Kg BB) were groups that were administered with ethanol extract of apple peel in 3 different dosages and exposed to smoke. The administration of apple peel ethanol extract and the smoke exposure were conducted in day 6 until day 19 of pregnancy. The research result data was analyzed using One Way Anova, Post Hoc Test and Pearson Correlation Test. Result: The weights of newborn rats on K+ group were smaller than K-and the difference was significant (p=0,004). Group P1, P2, and P3, had significant difference with K+, but not with K-. Conclusion: Apple peel's ethanol extract can prevent weight loss on newborn rat and the effective dose is 7mg/Kg BB. ABSTRAKLatar belakang: Angka Kematian Bayi (AKB) merupakan salah satu acuan pembangunan kesehatan yang tertuang dalam Rencana Pembangunan Jangka