Introduction The birth of a first child poses significant challenges to the couple relationship. In the context of a new well established trend to older maternal age at first birth, this paper had two objectives: 1) To describe the relationship context during the transition to parenthood for mothers of different ages and 2) to examine the impact of the transition to parenthood on relationship satisfaction and whether this differed according to age and mode of conception. Materials and Methods Participants were 619 nulliparous pregnant women (48%, n = 298, conceiving through ART), aged from 20-51 years, recruited between 2007 and 2009 from IVF clinics, antenatal clinics and antenatal classes. They were categorized into three age-groups < 30 years (“young” n = 188, 30%); 31-36 years (“mid” n = 226, 38%); > 37 years (“older” n = 205, 33%). Four months after birth 568[OU1] women (91%) participated in a follow-up assessment. Women were interviewed about their current relationship context and history and completed the Intimate Bonds Measure (IBM) in pregnancy and at 4 months postpartum. The Measure yields two subscales, Care (the extent to which partner shows warmth, affection) and Control (the extent to which partner tries to control or is critical of behaviour). High scores on Care and low scores on Control, respectively, indicate more optimal relationship adjustment. Results The relationship context prior to birth of a first child differed by age and mode of conception. Older mothers were less likely to be married (69% vs. 85% in both the middle and younger age-groups, P = .000, but more likely to have been married before (40% vs. 22% for the middle, 7% for the younger age-groups, respectively, P = .000). IVF women were more likely than spontaneously conceiving (SC) women to be married (82% vs. 76%), P = .02. Five of the six women in same sex-relationships were in the older age-group and all conceived through IVF. Older mothers and mothers conceiving through IVF had been longer with their partners prior to pregnancy, (Mean months: older = 94, mid = 77, young = 66, P = .000; IVF = 50, SC = 45, P = .000). A three (age-group) x two (mode of conception) x two (time) factorial analysis of variance examined relationship adjustment, controlling for duration of relationship, and relationship status. There was significant time effects for both Care, P = .000, and Control, P = .000, with higher scores for Control and lower scores for Care after the birth. There was also a significant age-group effect for Care, P = .000, but not for Control. Compared to mothers in the young age-group, older mothers rated their partners lower on Care on both occasions. The mid- age group did not differ from the younger and older age-groups. There were no significant interaction effects with a similar pattern of declining marital satisfaction (lower care and higher control) across age-groups, and according to mode of conception. Conclusions The overall decline in relationship satisfaction across the transition to parenthood is consistent with a large body of research, but few studies to date have examined age differences. Our results show that compared to their younger counterparts, older first-time mothers report lower perceived care, both in pregnancy and postnatally, and even after controlling for relationship duration. In other words, older mothers start childbearing at a relational disadvantage that persists through the first months postpartum. The mechanisms to explain this effect and directions for future research will be discussed taking account of a range of other contextual factors including marital status, employment, child characteristics, child care and social support.