Our study findings indicate that the mean BP and PIH levels were lower in rural Ghana than in urban Ghana. BMI and heart rate were independently related to a high systolic BP while urban residence and BMI were independently related to diastolic BP.
The low prevalence of PIH in rural (0.4%) and urban (3.1%) Ghana in our current study is more or less consistent with studies in SSA. In South Nigeria, a prevalence of 3.7% was found . For example, in rural areas of Zimbabwe a prevalence of PIH of 1.8% was found . Retrospective hospital based data also show low incidence rates in several African countries [19–21]. In one study in urban Gabon, a low incidence of 0.5% was found . In urban Ethiopia an incidence of 0.7% was found over a study period of 5 years (1994 – 1999) . Furthermore, a retrospective study in the Dar es Salaam found an incidence rate of 2% .
Although the prevalence rates in our study are somewhat consistent with studies in several African countries, the mean BP levels were extremely low in Ghana in both urban (105/66 mmHg) and rural (102/61 mmHg) areas when compared with other studies in SSA [23–26]. In Ethiopia, for example, women in the age group of 25–34 years had a mean BP of 117/77 mmHg while those in the age group of 35–44 years had mean BP of 122/79 mmHg . Similarly, in urban Tanzania the age group of 15–34 had a mean blood pressure of 119.7/78.1 mmHg, and in rural Tanzania this age group had a mean blood pressure of 115.9/72.5 mmHg . Furthermore, the mean blood pressure levels are far lower than those reported among non pregnant women with the same age range in Ghana. In one study in rural parts of Northern Ghana, the mean systolic and diastolic BP levels for the age group 15–24 years, 25–34 years and 35–44 years were 114/66 mmHg, 113/68 mmHg and 123/76 mmHg, respectively . Usually the diastolic blood pressure decreases between 5 mmHg to 10 mmHg during week 12–26 of the pregnancy . So the mean BP levels of 105/66 mmHg in urban and 102/61 mmHg in rural Ghana in this study are quite low compared to the previous found BP levels among women in these age groups. The explanations for the low mean BP levels among Ghanaian pregnant women are unclear and further studies are needed to establish the potential underlying factors.
In both rural and urban Ghana, BMI, heart rate and a family history of hypertension were independently associated with an increased BP. These findings are consistent with previous studies carried out in SSA [23, 27–31]. For diastolic BP, the difference between rural and urban Ghana could be partially explained by a difference in mean BMI and number of women with a family history of hypertension, though another unknown factor might have contributed to the difference in diastolic BP.
BMI was the strongest factor for differences between urban and rural Ghana. In the multiple linear regression analysis, BP difference between urban and rural Ghana was partially explained by the difference in BMI. This observation is consistent with a recent report in China. In Liu et al’s study in China, the incidence of PIH tends to rise with an increasing BMI . Overweight and obesity are an increasing problem in cities of Ghana. Left unchecked, the increasing prevalence of overweight and obesity in Ghana will exacerbate PIH levels in Ghana.
Some limitations were inherent to our study design. As in many surveys, the BP levels were based on the average of two measurements at a single visit, which might have overestimated the prevalence rates due to white-coat hypertension . The urban sample was based on only one hospital in the Ashanti region, unlike the rural sample which was based on different health facilities in the Brong-Ahafo region. It is possible that the characteristics of the study population may differ from other urban hospitals and could influence our study results. Nevertheless, because it is located in the university grounds, it serves a population with a high degree of variation in socioeconomic status. Besides, the urban sample was relatively small.
The assessment of gestational age was based on last menstrual period recorded in midwifery notes in rural Ghana and ultrasound in urban Ghana, which might influence the our study results . In addition, the urban and rural data collections were performed in different months of the year and therefore bias for timing might be present. TePoel et al. found a difference in prevalence of PIH between wet and dry seasons in tropical countries . Nonetheless, data collection in both rural and urban Ghana was carried out mainly in rainy season (i.e. April to October), therefore the influence of seasonal differences in data collection is likely to be small.
Overweight and obesity measures in our study were based on BMI during pregnancy, which might not be a true reflection of overweight and obesity because of changes in weight during pregnancy . In many studies pre-pregnancy BMI or weight gain during pregnancy was used to assess overweight or obesity. Unfortunately, since most pregnant woman in rural Ghana do not know their pre-pregnancy weight, it was not possible to assess this in our study. Caution is therefore needed regarding the interpretation of our result on this.
Despite these limitations, the current study still provides very important information on one of the important risk factors for poor maternal health outcomes.