The subject matter of this thesis is the measurement of family cohesion. It includes the related theme of the impact of the birth of a child with a congenital malformation on family cohesion. The concept of family cohesion has emerged over a history of almost 50 years of marital research. This thesis presents a comprehensive review of the concepts that have evolved, and of the instruments that have been developed to measure themes inherent in this subject. These themes have included marital success, marital happiness, marital adjustment, marital pathology, marital solidarity, marital stability and family cohesion. A selective review is also presented of the vast and conflicting literature which concerns the impact on the family of a child with a chronic illness or a handicapping condition. In some earlier studies it has been reported that in such families divorce and separation rates are increased and satisfaction within the marriage is reduced. Conversely, other studies report that family breakdown is not increased in these families. Indeed, some reports have suggested that the presence of a sick or impaired child can enhance the cohesiveness of the family and draw the members closer together as a family unit. The answer to this question is of great practical importance, as there are preventive implications if the former situation exists in fact. Most previous studies of this subject have used pre-selected (non-representative) populations for study. Such selection makes confident interpretation of results impossible. To generate further knowledge in this area, this thesis reports the results of a major seven-year prospective study. The aims of this study were -( 1) To develop and test a new scale measure of family cohesion (The FAMCOH SCALE) which would be useful both as a research tool and as a practical aid in family assessments.(2) To compare the FAMCOH SCALE with the Spanier Dyadic Adjustment Scale.(3) To study the impact on family cohesion of the birth of a child with a congenital malformation using the Spanier Scale and the FAMCOH SCALE.( 4) To study the impact of the birth of a child with a congenital malformation on the mental health of the mother. The FAMCOH SCALE was developed using the following steps;1. A Delphi procedure was used to generate items considered important in family cohesion. 176 "experts" in marriage and human relationships were consulted in a three stage Delphi procedure.2. The themes generated from the Delphi procedure were converted into specific items for testing.3. Pilot testing was undertaken on 442 pregnant women. The results were subjected to factor analysis and reliability testing.4. The final result was a 17-item self-report questionnaire which comprised two sub-scales. For convenience, these sub-scales were named "Cohesion Index" and "Monetary Adjustment Index". One major potential strength of this new scale (above others) is the inclusion of the Monetary Adjustment Scale - an area of family functioning which has been overlooked or underemphasized in previous scale measures. The resulting 17-item scale had a Chronbach's Alpha reliability of 0.87 and a correlation of 0.61 with the Spanier Scale. Test-retest (short term) correlation of the FAMCOH SCALE was 0.75. Regression analysis revealed that the FAMCOH SCALE and the Spanier Dyadic Adjustment Scale have a commonality to the extent that 64 per cent of change in score on the FAMCOH SCALE is accounted for in change in score on the Spanier Dyadic Adjustment Scale. Regression analysis also showed that there wa a relationship between income and FAMCOH SCALE scores for some defined levels of family income, but no relationship between cohesion and length of the relationship. The second major part of this thesis comprises a pair-matched case-controlled prospective longitudinal study of the impact on family cohesion of the birth of a child with a congenital abnormality. Case selection was undertaken from a cohort of 8556 consecutive volunteer women enrolled in the Mater Obstetric Outcomes Study at the Mater Misericordiae Hospital, Brisbane. After the birth of the infants to the 8556 women enrolled in this study, those with congenital malformations were assessed, and ranked in order of severity as perceived by six paediatricians. Eighty-two consecutive surviving children were selected from among those with the most severe conditions. The families of these children comprised the index group for the study. A control group was selected by matching each index group child with a control group (normal) child, matched on ten characteristics known to affect family cohesion, including age of the mother, sex of the child, position in the family, occupational status of the father (or mother's partner), previous marriage of mother, previous marriage of partner, birth weight of the child, race, frequency of church attendance and age of the mother's partner. Data was obtained at four time periods; the first antenatal visit, the period three to five days after the birth of the child, when the child was six months old, and when the child was five years of age. Data obtained included socio-demographic data collected at the antenatal visit. The following instruments were used to obtain measures at the first three time periods: the Spanier Dyadic Adjustment Scale and the Foulds-Bedford Anxiety and Depression Scales from the Delusions-Symptoms-States-Inventory. In addition to a re-administration of the Spanier Dyadic Adjustment Scale the FAMCOH SCALE of family cohesion and the Questionnaire on Resources and Stress were administered when the children were five years of age. Data on the children were also obtained from a questionnaire on obstetric data gathered at the time of the birth and completed by the obstetrician. The results of this study suggested that -(I) There was no greater incidence of divorce or separation over the first five years in families who produced a child with a congenital abnormality. Individual exceptions are known; however collectively, children with survivable physical disabilities do not increase the rate of family breakdown. (2) No difference was recorded in marital adjustment over the first five years of the child's life between families with a child with a congenital abnormality and those with no abnormality. Measures of marital adjustment indicated that inter-spouse adjustment fell following the birth of a child for the families with normal children, and for the families with a child with a congenital abnormality. (3) There were no differences in measures of anxiety or of depression between the index mothers (i.e. those with children with congenital malformations) and control group mothers over the first six months of the child's life. (4) No difference (families with congenital malformations versus normal children) was found in response to the Questionnaire on Resources and Stress. This reflected the similarities in the perception by the mothers of the children with abnormalities compared with those with no abnormalities, in spite of the children being selected from those with the most severe abnormalities. This research provides support for the hypothesis that children with congenital malformations are not a disruptive influence within families, at least from the maternal perspective.