A study of the value of a self reported family history of pregnancy hypertension or cardiovascular disease as a predictor in the development of pregnancy-induced hypertension

Pregnancy-induced hypertension (PIH) is a common complication affecting approximately 20% of women. Despite improved health of women and the availability of antenatal care, it remains a major cause of maternal mortality and perinatal morbidity and mortality. The condition has been recognised for centuries, however its aetiology remains uncertain. Numerous studies have suggested that familial factors are associated with susceptibility to develop PIH, although the genetic basis of the condition is not clear. The purpose of this study is to investigate the value of a family history of hypertension in pregnancy or cardiovascular disease, as reported by the woman herself in predicting the development of PIH. The sample consisted of 1181 primigravid women who booked for antenatal care, within the first trimester of pregnancy, at Glasgow Royal Maternity Hospital. Following return of a self report questionnaire and collection of data on pregnancy outcome, complete data was available for 955 women. This study used a prospective cohort design. A simple questionnaire was developed asking about family history of pregnancy hypertension in mothers, sisters, aunts and grandmothers. Additional questions were asked about the occurrence of cardiovascular disease (hypertension, heart disease and stroke) in close family members. As the purpose of the study was to assess the value of information provided by the women themselves in predicting PIH no attempt was made to verify information given, by tracing case records of family members. Case records of all women entered into the study were followed up for outcome of pregnancy. Data were analysed for overall incidence of PIH and in particular for incidence in groups of women who reported either positive or negative family history of hypertension in pregnancy or cardiovascular disease. The study found that the incidence of a reported family history of pregnancy hypertension was high (35.7%). The incidence of reported family history of cardiovascular disease was also high (49.1%). In contrast the incidence of PIH, in particular severe disease, within women in the study was low (14% for all PIH, 1.4% for severe). The odds ratio for development of mild PIH and for PIH requiring therapy were significantly increased in women who reported that a member of their family had been affected by pregnancy hypertension compared to those who reported that they had no such history (1.56 and 2.0 respectively). However the odds ratio was not significantly increased for women who developed moderate and severe disease. The questionnaire also identified a group of women who reported that they had no family history of disease. The incidence of PIH amongst these women was significantly lower than that in women who reported that they had a family history of either pregnancy hypertension or cardiovascular disease (11.1% versus 15%). Women who reported that they had a sister who had been affected had a particularly high incidence of PIH (28.5%) When this group was compared to the women who reported no family history the odds ratio was significantly increased for development of all types of PIH. However in the more clinically meaningful comparison with the study group as a whole the odds ratio was only significantly increased in relation to mild disease. The study investigated the affect of a reported family history of cardiovascular disease on development of PIH. In comparison with the group of women who reported no history, women who gave a family history of essential hypertension had an increased odds ratio for development of PIH, in particular mild disease (odds ratio 1.97). Those who gave a family history of cardiac disease had an increased odds ratio (2.27) for moderate and severe disease. Information provided by women themselves on family history of pregnancy hypertension and cardiovascular disease did identify risk groups for subsequent development of PIH. In a clinical setting this information may be of value as part of an assessment of individual women's risk of developing PIH and in planning antenatal care. However, even within the highest risk group the incidence of severe PIH remained low, most women remaining normal throughout pregnancy. Correspondingly within the lowest risk group, although the incidence of severe disease was low it did occur in some women. Based on the data of this study it would appear that information on family history of pregnancy hypertension or cardiovascular disease, provided by the woman herself would not be of clinical value as a screening test for predicting the development of PIH. The questionnaire was acceptable to most women within the study, and may be useful in identifying affected family groups for further research into the genetic basis of PIH