Childlessness has caught attention in the past decades as it may show a new way of life style and great influences on the female life course in many aspects. The increase of childless people is observed throughout Europe, North America, and Japan. Accompanied by this trend, the mean age at first childbirth has also increased. However, it has not been clearly investigated which phenomena: remaining childless or postponing first birth, is mainly happening. The aim of this study is to quantify those effects using a decomposition method. We employ the classical life table method to measure the changes in first childbirth behavior. Life expectancy is normally used in mortality research to present the average length of years person alive. In childlessness (first childbirth) research, life expectancy signifies the expected years without children as the event focused is a firstbirth. Thus, we define the expected years without children age 15 to age 49 (EYWC) using Coale-McNeil model. To avoid truncation and censoring problem, only completed cohort fertility data of 8 selected countries is taken from Human Fertility Database. EYWC is decomposed into three factors: remaining childless, postponing first birth, and expansion of the standard deviation of mean age at first birth. EYWC increased from 1940s birth cohort in Canada, Japan, the Netherlands, Norway and the USA. Sweden’s EYWC has remained in the same level after increasing in the 1940s, while Portugal fluctuated in 1940s and 1950s birth cohort before started increasing. The EYWC for Czech Republic has been broadly flat. Results of decomposition show that postponement is mainly occurred in North America and Northern European countries. Contrarily, remaining childless is observed as a main contributor in Japan and Portugal. The expansion effect is less important in the changes in EYWC for all periods and countries analysed.