The concept of the socioeconomic lifecourse is increasingly informing understanding of the social patterning of cigarette smoking. We investigated lifecourse influences on (i) women's smoking status (smoker/non-smoker) before pregnancy and (ii) quitting in pregnancy in the UK Millennium Cohort study. Our analyses included conventional measures of the socioeconomic lifecourse (woman's childhood circumstances, education, current socioeconomic circumstances) and measures of her domestic lifecourse (age of becoming a mother, current cohabitation status), as well as parity (first/subsequent child). In analyses of quitting, we also included pre-pregnancy cigarette consumption. Our study underlined, firstly, the importance of lifecourse disadvantage. Those experiencing greater disadvantage with respect to their childhood circumstances, education and current circumstances were at greater risk of being a smoker before pregnancy. A disadvantaged domestic lifecourse - earlier entry into motherhood and lone motherhood-further increased the risk. Poorer childhood circumstances, educational disadvantage, poorer current circumstances and early motherhood also significantly increased the odds of quitting in pregnancy. Secondly, parity was a major predictor of smoking behaviour. First-time mothers had higher odds both of smoking before pregnancy and quitting in pregnancy. The effects of parity were independent of women's lifecourse. Our study supports tobacco control policies which recognise and address inequalities across the lifecourse. However, our study suggests that the dye is not irrevocably cast by social disadvantage: first pregnancy uniformly increases the chances of quitting. Interventions which help smokers having their first baby to quit have an important part to play in promoting maternal and child health.