A women’s age at marriage is considered to be one of the most important variables accounting for variation in fertility levels among different societies of the world. The objective of the present paper is to study the fertility behavior of females near the time of marriage using the approach of first birth interval. The study is done in two sections. Section-1 deals with the study of spatial variation in first birth interval across different states of the country (India) for females classified according to age at marriage. It also deals with the investigation of transition of first birth interval from NFHS-2 to NFHS-3. Section-2 is concerned with the application of a simple model to investigate whether the assumption of constant fecundability after marriage till the occurrence of first conception is suitable or not. If so, the estimates of fecundability have also been obtained using simple technique of estimation.