Seniman Waruwu Pengarang Meiyana Sinaga, SST,MKM Dosen Pembimbing 1 Eni monaliska sihombing S.Tr, M.Kes Penguji 2 Ermita Silvana Simanungkalit, S.Tr.Keb.MKM Penguji 1

Family planning (KB) is an effort to regulate the birth of children, the ideal spacing and age of childbirth, regulate pregnancy, through permont, protection programs and assistance in accordance with reproductive rights to provide quality family justice. To achieve this, several casa or alternatives are made. contraception or preventing sperm from forming so that fertilization does not occur which results in pregnancy This type of research is an analytical survey with a cross sectional approach. The population in this study is mothers who use contraception for 3 months at the independent practice of midwife Mardiamom Satopel. In this study, the total population is used, namely where the entire population is used as a sample as many as 36 people. The research results suggest that the majority of mothers have the majority of knowledge, mothers who have knowledge in the poor category are 13 people (36.1%), and the minority of mothers who have knowledge in the sufficient category are 11 people (30.69%). Of the 36 respondents, 17 mothers (47.2%) experienced maximum weight gain and 19 mothers (52.8%) experienced a minority of mothers who did not experience weight gain. There is a relationship between the knowledge of women of childbearing age regarding the use of 3-month injectable contraceptives and weight gain at the 95% confidence level with a 0.05% obtained sig (2 sided) 0.000. So Ha is accepted and Ho is rejected, which means there is a correlation between the two variables of maternal knowledge and increase in weight. The conclusion of this study is that there is a relationship between fertility in women of childbearing age and increased body weight. It is recommended that mothers use contraception for 3 months. Keyowords : Knowledge of women of childbearing age regarding the use of injectable contraceptives for 3 months with increased weight Body Bibliography : 16 books, 10 online website