There were five infant mortality cases and two malnutrition babies occured in Sidengok Village, Pejawaran Subdistrict, Banjarnegara District year 2013. The main factor of the cases was low birth weight (LBW) as of the early marriages. The women in Sidengok used toget married at the average under 20 years, and even some of them married under 16 years. It was legally allowed because of “age session in court” as marital dispensation. The type of study was a qualitative method with an observation participation. The study aimed to identify social and cultural factors of LBW and infant mortality in Sidengok village. It revealed that the "age session in court" in Sidengok village, is a way to legalize marital status for the underage couple, causing LBW which is one of underlying factors of infant mortalities. On the other hand,‘the age session in court' such as marital dispensation is legally allowed and regulated in marriage law, which might have an impact on women's reproductive health. It concludes that the occurrence of "age session in court" in Sidengok village has been a common event which was legally supported by marriage laws. It recommends to decrease LBW rate and infant mortality rate, it needs an amendment of marriage law, in particular, a minimum age to get married.