In this paper we attempted to modify Bongaarts' model considering all fetal wastage for estimating approximately true value of TFR. Also, it was found the effect of proximate variables on change the level of fertility during 1975 to 2007 in Bangladesh. For this study, data were extracted from Bangladesh Contraceptive Prevalence Surveys, Bangladesh Fertility Surveys and Bangladesh Demographic and Health Surveys. Proximate determinants influence the level of fertility in a society. Bongaarts' model is a well known approach for studying proximate determinants for total fertility rate (TFR) of a society. Only induced abortion as one of the proximate variable is considered in Bongaarts' model for estimating proximate determinants of fertility, though the other possible factors like miscarriage and stillbirth are also important for fertility. The TFR was estimated by revised model was more close to observed TFR (R2=0.98) than TFR calculated by Bongaarts' original model (R2 = 0.84). Moreover, only abortion (Bongaarts' model) put contribution to change TFR approximately 1 birth while all fetal wastage (revised Bongaarts' model) change TFR approximately 1.40 birth per women. This study demonstrates that all proximate indices shows decreasing tendency over time. The results suggest that revised Bongaarts’ model more accurately estimate TFR than original Bongaarts' model.