Although the transition to parenthood is generally defined as the period from pregnancy to several months after birth, it can also be differently defined due to other important changes that involve much more than the birth of the child. The transition to parenthood is one of the most challenging times during the early stages of a partnership. Starting with the first study in this area, in which 83% of couples witnessed an “extensive” or “serious” crises in which they found themselves adjusting to major life changes in that period of life (LeMasters, 1957, cited in Kluwer, 2010), many researchers found a decline in marital quality and satisfaction after the birth of the first child (e.g., Ahlborg, 2004; Belsky & Rovine, 1990; Cowan & Cowan, 1995; Čudina-Obradović & Obradović, 2006; Twenge et al., 2003). Although there are many forms of support for parents in their transition to parenthood, most women, over 85% of them, still feel unprepared for this change (Renkert & Nutbeam, 2001) and are very often overwhelmed by the new role (Nelson, 2003). In most studies, researchers found a sharp decline in relationship satisfaction after the birth of the first child (Doss et al., 2009; Kluwer & Johnson, 2007; Lawrence et al., 2008; MacDermid et al., 1990; Shapiro et al., 2000). Notably, Twenge et al. (2003) analyzed 97 published studies and unpublished dissertations in the meta-analysis that included both longitudinal and cross-sectional research designs. Their results confirmed that parents reported significantly lower marital satisfaction than childless couples, but also showed that the magnitude of these effects is small. Women reported lower marital satisfaction than men, with the magnitude of the effect for gender differences being significantly greater than the magnitude of the effect for differences between those who become parents and those who have not. Men rate relationship satisfaction higher than women in other periods of life too (Devine & Forehand, 1996). In the transition to parenthood, women report a stronger, earlier, and faster decline in relationship satisfaction in comparision to their partners (Grote & Clark, 2001; Twenge et al., 2003). Women report a decline in relationship satisfaction as early as the first months after childbirth, while men confirm a more gradual decline in relationship satisfaction only six months later (Feeney et al., 2001). One of the explanations for gender differences in relationship satisfaction are gender roles. With the birth of a child, there is a clearer differentiation of gender roles in which the stereotypical division into female and male responsibilities becomes more prominent in the direction of women taking over most household chores (Grote & Clark, 2002; Kluwer & Mikkula, 2002). The increased workload is not the cause of the problem per se. Unfulfilled woman’s expectations of a more equitable division of labor after childbirth is often the cause of women dissatisfaction (Kluwer & Mikula, 2002; Van Egeren, 2004). Body image is the way that an individual experiences his/her body. Nezlek (1999) emphasizes that body image consists not only of the perception of body appearance, but also includes a component of attraction as well as a sexual dimension. Body dissatisfaction is very common in women (Frederick et al., 2007), so much so that it has become practically “normal” in Western societies (Furnham & Greaves, 1994; Striegel-Moore, 1995). Research has shown that women with a more positive image of their own body show higher levels of sexual desire and pleasure. They have more frequent and better sexual intercourse, lower levels of sexual anxiety, avoidance and dysfunction, and higher levels of sexual adjustment (Hoyt & Kogan, 2002; Pujols et al., 2010; Seal et al., 2009; Wiederman & Hurst, 1998). Pregnant women and young mothers generally witness a significant deterioration in body image due to physical changes occurring in pregnancy and the postpartum period (von Snydow, 1999; Mickelson & Joseph, 2012). Some research suggests unchanged satisfaction with the body during pregnancy but also its decline after childbirth (Pauls et al., 2008). Longitudinal monitoring of the group of women who became mothers and those who did not revealed a decrease in the self-assessment of maternal attractiveness between pre- and post-pregnancy periods, while growth in the assessment of self-attractiveness in the same period was present in the group of women without children (Cast, 2013). Documented weight increase in males during their partner's pregnancy is 6.3 kilograms on average (Belkin, 2009). In contrast to women, new fathers experience an increase in their sense of attractiveness after the birth of their child, which is explained by strengthening of sense of masculinity and income increase which often comes with an increased family. This can lead to more positive assessments of physical attractiveness (Cast, 2013). Female body satisfaction has been shown to be significantly associated with sexuality in pregnancy (Nehzad & Goodarzi, 2011). In rare studies that included variables of both interpersonal and intrapersonal functioning, it has been found that sexual satisfaction of women during pregnancy is more defined by the characteristics of a partnership than by their body satisfaction (e.g., Nakić Radoš., Soljačić Vraneš & Šunjić, 2014). Sexuality is both a very important domain of close relationships and a relevant factor in emotional and physical health (Bridges et al., 2004). Moreover, women and men emphasise sexual pleasure as one of the most important factors of couple well-being (Trudel, 2002). During the transition to parenthood, couples report a decline in the importance of sexuality in the postnatal period, as well as a decline in satisfaction with current sex life (DeJucibus & McCabe, 2002). In general, women report declines of various aspects of sexual functioning such as sexual desire (Bogren, 1991; DeJucibus & McCabe, 2002; Sagiv-Reis et al., 2012), sexual activity (Al Bustan et al., 1995; Bartellas et al., 2000; Nakić Radoš et al., 2014), sexual enjoyment (Sagiv-Reis et al., 2012), and sexual pleasure (Serati et al., 2010) during pregnancy. Decreased sexual functioning is also present during the first few months after the birth of a child (De Jucibus & McCabe, 2002; Serati et al., 2010; vonSnydow, 1999), while the quality of sexual relations is an important factor in overall life satisfaction of spouses after birth of a child (Ahlborg et al., 2005). According to gender stereotypes, sexual satisfaction is more important for marital satisfaction of men than for women (Karney & Bradbury, 1995). There is some research evidence of higher sexual satisfaction of women compared to men (Rehman et al., 2011), but other research yielded opposite results (Ji & Norling, 2004), and still others did not find gender differences in sexual satisfaction (Sánchez-Fuentes et al., 2014). Overall, sexuality of men during the transition to parenthood has been neglected in research. Men do not report significant changes in sexual interest and desire until the third trimester or even during the whole pregnancy (Nakić Radoš et al., 2015; von Snydow, 1999; Yidiz, 2015). Since, in determining overall relationship satisfaction, sexual satisfaction is more important for men than for women, it is reasonable to assume that deterioration in sexual functioning during the transition to parenthood (vonSnydow, 1999) will have a more negative effect on men and thus more successfully predict their overall relationship satisfaction. It should be taken into account that this area of research has so far been neglected, i.e., that there have been two separated "streams" of research, one focused on sexuality in general and the other on partnerships (Impett et al., 2014). There is a great need for research that will answer questions about how the processes within partnerships and different aspects of sexual functioning are interconnected. It has been noted that a high level of intimacy can have a “protective function” for partnership functioning during a period of life in which many couples have an unsatisfactory sex life (Nezhad & Goodarzi, 2011). More precisely, in couples with a high level of intimacy, despite low sexual satisfaction, marital satisfaction remained high. Andersen and Cyranowski (1994) described a construct within sexual self-perception that encompasses cognitive aspects of one's own sexuality and refers to what an individual thinks of himself/herself as a "sexual being." They named it a sexual self-scheme. Andersen and Cyranowski (1994) postulated that sexual-self schema manifests in current sexual behavior and cognitions and may serve as a predictor for future behaviors related to an individual’s sexuality. The results of the only two studies on the relation between the sexual-self scheme and the quality of the relationship are contradictory. From older research, we can conclude that women's experience of their own sexuality is not relevant for their relationship satisfaction, while sexualself schema explained a significant part of the variance in men's relationship satisfaction (Aaerstadt, 2000). In the same study, a positive sexual-self scehma in men was positively associated with their level of relationship intimacy. The results of more recent research (Kohlberger, 2011) are consistent with research on the correlates of female sexuality (e.g., Cooper et al., 1998) and suggest that women associate sex with romantic feelings more than men and will engage in sexual relations with a partner for the purpose of achieving intimacy or other reasons related to the establishment or maintenance of a partnership. Kohlberger (2011) found that it was the female sexual self-schema that was positively associated with relationship satisfaction, whereas this association was not confirmed in male participants. Unambiguous conclusions cannot be drawn from extant research on the relationship between sexual selfschema and sexual pleasure. For example, moderate levels of sexual satisfaction have been found in both women with positive and negative sexual-self schemas (Cyranowski & Andersen, 1998). Some research has confirmed an association between a positive sexual-self schema and higher sexual satisfaction in women (Relline & Meston, 2011; Aaerstadt, 2000; Mueller et al., 2016). In studies in which men also participated, a positive association was found between a positive view of one's own sexuality and higher levels of sexual satisfaction (Mueller, 2015) but the absence of this relation has also been reported (Aaerstadt, 2000). Sternberg combined three dimensions of interpersonal relationships in order to explain love. He linked intimacy, passion, and commitment in the triangle that could define the kind of love that one person feels for another (Sternberg, 1997). It seems that women and men do not differ in their assessment of love (Gao, 2001) although there are some studies that attribute a higher level of passion to men and less intimacy to women with very small and inconsistent differences (Sumter et al., 2013). Love is found to be the most important factor of relationship satisfaction (Kaslow & Robinson, 1996; Obradović & Čudina-Obradović, 2000). Percieved fairness in marriage is defined as the principle of fairness, proportionality or equality of contributions, and gains from the relationship (Sprecher & Schwartz, 1994). In addition to balance in housework and childcare, women and men determine equity based on emotional characteristics of the relationship, such as taking into account the partner's feelings and needs and undesirable behaviors, such as unjustified accusations and complaints and aggressive outbursts (Lerner & Mikula, 1994 ). Perceived justice in marriage is associated with marital satisfaction (Grote & Clark, 2001; Lacković-Grgin et al., 2009). Women perceive justice in marriage lower than men, especially if members of the same couple are compared (Ćubela Adorić, 2001; Sprecher & Schwartz, 1994). In this paper, we drew from several theoretical models to predict differences in specific aspects of partner relationship in different stages of the transition to parenthood. Based on the family systems theory (Klein & White, 1996), we expected that pregnancy and parenthood would disturb balance in the partner subsystem and that partners will experience certain difficulties in adapting to this major life change (in body satisfaction, sexual self-perception, and satisfaction and relationship quality). Furthermore, starting from the triangular theory of love (Sternberg, 1997 ), we explored whether the transition to parenthood is a time period in which differences in the intensity of love can be determined between those who do not have children and those who are expecting or have a child. We also hypothesized that love predicts relationship satisfaction at all stages of the transition to parenthood. Finally, based on the model of sexual dissatisfaction (Twenge et al., 2003), we expected that the arrival of a child would have negative effects on the sexual life of new parents and that men's sexual satisfaction will be a stronger predictor of relationship satisfaction than sexual satisfaction of women. The aim of this dissertation was to investigate body image, sexuality, and the relationship quality in different stages of transition to parenthood. We attempted to answer two specific research questions (RQs). RQ1: Are there differences in body image, sexual self-perception, sexual satisfaction, and the relationship quality in different stages of the transition to parenthood? RQ2:Are there differences in contributions of body image, sexuality, and relationship quality to overall relationship satisfaction in different stages of transition to parenthood? Four groups of women and men (a total of 325 couples) from several Croatian cities participated in the study. The snowball method was used to collect data from the first group (n = 174), which consisted of women and men without children. Participants from the second group (n = 186) were women and men expecting their first child (pregnant women and their partners). We collected their data in gynecological policlinics and pregnancy courses in health centers and hospitals. Women in this group were in the last trimester of pregnancy, so the sample was relatively homogeneous with respect to the duration of pregnancy. Third (n = 148) and fourth (n = 142) group consisted of parents of six-month-old and one-year-old children who were given questionnaires during pediatric check-ups in health centers. Because these groups were convenience samples in the cross-sectional study, we paid special attention to the inclusion/ exclusion criteria and control variables to ensure, as much as possible, the uniformity of the groups that we compared. The inclusion criterion for all (adult) women and men was the experience of cohabiting for at least six months, since the dynamics of the partnership between couples living together and those who are dating are significantly different. The inclusion criterion in the group of women and men without children was that they wanted to have children together in the future, since women and men who do not intend to achieve parenthood could also differ in some important features related to the subject of research from those who have that intention or those who have already begin the transition to parenthood. The study included women and men who are both expecting their first child conceived naturally and those who have their first healthy six-months-old and one-year-old child born from a pregnancy without complications. The experience of complications in pregnancy and the experience of parenting a sick child is significantly different from the transition to parenthood without such experience. We grouped our focus variables in five categories: preparedness for parenthood, body image (body satisfaction and body image self-consciousness), sexual self-perception (sexual satisfaction and sexual self-scheme), relationship quality (love and perceived fairness in marriage), and overall relationship satisfaction. The Preparedness for Parenting Scale was constructed for the purpose of this research. We used The Body Areas Satisfaction Scale (part of a more extensive Multidimensional SelfBody Attitude Questionnaire (Brown et el., 1990) and Body Image Self-consioussness Scale (Wiederman, 2000) to measure body image. Sexual self perception was operationalized with the Sexual Self-schema Scale (Hill, 2007) and New Sexual Satisfaction Scale (Štulhofer & Buško, 2012). We applied Sternberg's Triangular Love Scale (Sternberg, 1997) and three questions from Perceived Fairness in Marriage Scale (Ćubela Adorić & Mičić, 2010) as indicators of relationship quality. We used the Quality of Marriage Index (Norton, 1983) to measure our criterion variable. Participants in this research reported high values in preparedness for parenthood, body image, sexual self-perception, relationship quality, and overall relationship satisfaction and low values of body image self-consciousness. In order to answer RQ1, we conducted a mixed ANOVA with phase of transition to parenthood as the independent factor (with four levels) and the gender variable as a repeated measurement (because the men and women in our sample were partners). We tested the effects of gender and the transition phase to parenthood on the perception of preparedness for parenthood, body image (body satisfaction and body image self-consciousness), sexual self-perception (sexual satisfaction and sexual self-scheme), relationship quality (love and perceived fairness in marriage), and overall relationship satisfaction. In order to answer RQ2, we conducted four separate hierarchical regression analyzes (HRA), one for each phase of the transition to parenthood. In HRA, relationship satisfaction was a criterion variable, and predictor variables were introduced into the six-step regression equation. In the first step, control variables (gender, age, relationship length, and education) were introduced. In the second step, a preparedness for parenting was introduced. In the third step, the variables representing body image were introduced (body satisfaction and body image selfconsciousness). In the fourth step, variables of sexual self-perception (sexual self scheme and sexual satisfaction) were introduced. The fifth step consisted of variables of relationship quality (love and perception of fairness in marriage). In the sixth step, we successively tested the moderation role of gender for each of the predictors introduced in steps one to five. Participants in different stages of transition to parenthood in this study differed only in their preparedness for parenting. Parents of six and 12-month old children reported higher preparedness for parenthood than couples without children. Pregnant couples and childless couples who plan to have children but not in the near future probably have not thought much about whether they are ready for parenthood and what it could bring. In addition, women and men who are expecting a child are probably more focused on the pregnancy itself and the upcoming birth than on parenting. Men and women who already have children can assess more accurately whether and to what extent they were prepared for parenthood because they now know exactly how many demands and changes a new family member has caused. The changes that a child brings to the previous dyad are so extensive that parents in many cultures feel unprepared for the experience (Borg Xuereb et el., 2012; Condon et al., 2004). Equal levels of body image were found in all groups of participants, as we expected. More specifically, men’s body image in all stages of the transition to parenthood was equal, while in women there was a slight trend toward poorer body image of women who have given birth compared to women without children and pregnant women. Social expectations probably make women much more sensitive to their physical appearance than men˗even pregnant women feel expectations about gaining control of their body after the birth of a child and describe these expectations as a “project” that they are expected to begin after childbirth (Clark et al., 2009; Upton & Han, 2003). We expected to find differences in sexual self-perception, relationship quality, and overall realtionship satisfaction between couples without children, those expecting their first-born child and parents of small children. Results showed that men and women in different phases of transition to parenthood reported very similar levels of sexual self-perception and satisfaction, love, perceived marital justice, and overall relationship satisfaction. These unexpected results can be explained by characteristics of the participants, especially their very high estimates of sexual and relationship satisfaction in general. When the initial estimates on a variable are very high, this is called the "ceiling" effect, which makes it more difficult to register significant differences in the subsequent phases of research in longitudinal studies, but also those between different groups of participants in cross-sectional studies. An important reason to explain the very high level of major variables is the sampling process itself. It is reasonable to assume that participants who (voluntarily) completed the questionnaires were those who found the topic of their relationship and sexuality more pleasant than those who refused to complete the questionnaires. Sexuality research has shown that voluntary participants report richer sexual experience, lower levels of sexual guilt, and less traditional attitudes about sexuality than those who do not want to participate in research on the same topic (Plaud et al., 1999; Wiedermann, 1999). It is also possible that well-functioning in the couple and high general satisfaction with the relationship acts as protection against a decline in sexual self-schema and sexual satisfaction or as a factor contributing to their smaller decline. Although the frequency of sexual intercourse is highly associated with sexual pleasure, Nakić Radoš et al. (2014) found that sexual satisfaction in the third trimester of pregnancy is weakly associated with sexual activity and moderately with intimacy, relationship satisfaction, and communication, suggesting a complex relation between different indicators of sexual satisfaction during the transition to parenthood. It is also possible that differences in mean values that we found would have reached the level of statistical significance and confirmed our hypotheses if we had larger samples. In almost all observed variables in this study, gender differences were recorded, all in the same direction. Compared to men, women showed lower preparedness for parenthood, as well as lower levels of body image and sexual and overall satisfaction with the relationship. Women only assessed their sexual self-schema and perceived justice in marriage as high as their partners. These findings are consistent with previous studies where numerous gender differences have been found, indicating a disadvantage of young women and mothers in comparison to their partners. Very likely, this disadvantage reflects the traditional environment in which young couples raise their children. Indicators of individual and partner functioning have successfully predicted overall satisfaction with the relationship at all stages of the transition to parenthood. Socio-demographic characteristics such as age, education, and relationship duration were the least successful predictors but it was important to control their effects when testing the predictive power of other variables. Preparedness for parenting successfully predicted overall relationship satisfaction until the introduction of relationship quality variables in all groups. This emphasizes the practical importance of preparing future couples for parenthood because this sense of readiness, even after numerous changes in body and sexual functioning, contributes to the overall satisfaction with the relationship. This finding also implies the protective effect of relationship quality on relationship satisfaction because even in the case of weaker or worse preparedness for the changes that a child brings, love and perceived justice in marriage can in some way "protect" partners deterioring in relationship satisfaction. Indicators of body image were not significant predictors of relationship satisfaction in women and men without children, which suggests that in this phase of the transition to parenting body image is not important in the context of a partnership. In couples without children and with a 12-month-old child, sexual satisfaction successfully predicted relationship satisfaction in all steps of the analysis. In pregnant couples, both indicators of sexual self-perception (sexual satisfaction and sexual selfscheme) were significant only at introduction, and by adding new variables they lost the power of predicting overall satisfaction with the relationship. This points to the previously mentioned reduced importance of the sexual aspect of functioning in couples expecting a child compared to those with young children. It is possible that anticipation of a new member and an increased sense of togetherness work so that sexual self-perception no longer has the power to predict relationship satisfaction when the emotional aspects of that relationship are taken into account. Some objective limitations during sexual activities, caused by changes in the physical plane caused by pregnancy, could also contribute to this. A similar finding of couples without children and those with one-year-olds may be an indicator of the return of sexual functioning in couples who had their first child a year ago to pre-pregnancy levels (vonSydow, 1999). Love and the perception of justice in marriage as indicators of relationship quality most successfully predicted overall satisfaction with a relationship in our set of predictors, which confirms the previously noted great importance of the emotional level of connection for relationship satisfaction (Kaslow & Robinson, 1996; Obradović & Čudina-Obradović, 2000). In addition, importance of love is bigger in groups with or expecting their first child, while sexual self-perception and sexual satisfaction are more important for participants without children who are in shorter-term relationships. Participants in shorter-term relationships had less time and opportunity for their personal development, as well as for developing various aspects of their relationship and that is why they might appreciate the sexual aspect of relationship more than those who are in relationships of longer duration (couples expecting their first child and parents of small children). Special attention should be paid to the finding that tells us that during the transition to parenthood for women expecting their first child and those who are mothers, but not for men, the importance of perceived justice in marriage is a very important predictor of their overall relationship satisfaction, probably due to the increased workload within the family community.