Journal of Obstetrics and Gynaecology, February 2015; 35: 153–154 © 2014 Informa UK, Ltd. ISSN 0144-3615 print/ISSN 1364-6893 online DOI: 10.3109/01443615.2014.948815
OBSTETRICS
Seasonal variation and hypertensive disorders of pregnancy in eastern Sudan A. A. Ali1, G. K. Adam2 & T. M. Abdallah1
J Obstet Gynaecol Downloaded from informahealthcare.com by Dalhousie University on 04/13/15 For personal use only.
1Faculty of
Medicine , Kassala University, Sudan and 2Gadarif University, Gadarif, Sudan
The aim of this study was to investigate the seasonal variation and hypertensive disorders of pregnancy in eastern Sudan, in the period between January 2008 and December 2010. The medical files of women attending at Kassala hospital, eastern Sudan with hypertension, with or without proteinuria were retrospectively retrieved. The data of patients with hypertensive disorders of pregnancy were compared with a similar number of controls that were normotensive and non-proteinuric. During the study period, there were 9,578 deliveries; 153 patients had hypertensive disorders of pregnancy, yielding an incidence rate of 1.6%. Of all cases and controls (306), there were 183 (59.8%) deliveries in winter, 84 (27.5%) in summer and 39 (12.7%) in autumn. The highest rate of pre-eclampsia was in winter (1.1%) (CI ⴝ 1.1–2.7, OR ⴝ 1.7, p ⴝ 0.004) and the lowest rate was in autumn (0.2%) (CI ⴝ 0.4–1.8, OR ⴝ 0.8, p ⴝ 0.758.). Our study revealed significant association between the incidence of hypertensive disorders of pregnancy and the winter season (103 (67.3%) vs 80 (52.3%), p ⴝ 0.001). Thus, more attention in the winter season might reduce the morbidity and mortality of hypertensive disorders of pregnancy. Keywords: Hypertension, pre-eclampsia, season, Sudan
Introduction Hypertensive disorders of pregnancy remain a major cause of maternal morbidity and mortality, the aetiology is not yet clear, however many risk factors have been demonstrated, such as age, obesity and multiple pregnancy (Luealon and Phupong 2010). Maternal mortality is extremely high in Sudan, with pre-eclampsia\eclampsia accounting for 4.2% of the obstetric complications in Kassala, eastern Sudan, which represents 18.1% of the direct causes of maternal deaths (Ali et al. 2012; Ali and Adam 2011). Some studies have suggested that pre-eclampsia might be affected by seasonal variation. Thus, the current study was conducted to evaluate the association between hypertensive disorders with pregnancy and different seasons in Kassala, eastern Sudan.
tensive disorders of pregnancy were compared with a similar number of controls that were normotensive and non-proteinuric. The controls were women who delivered immediately after the index case, we did not match them for any characteristic and their pregnancy was uneventful. High blood pressure was defined as two repeat readings 4 h apart of a blood pressure measurement of ⱖ 140\90 mmHg after 20 weeks’ gestation. Proteinuria was defined as ⱖ 2 ⫹ protein by dipstick in previously non-proteinuric women. According to the US National Institutes of Health (NIH), the cases were further sub-categorised into gestational hypertension (high blood pressure without proteinuria); chronic hypertension; pre-eclampsia-eclampsia; and pre-eclampsia superimposed upon chronic hypertension. Again, according to the hospital protocol, severe cases were defined as two repeat readings 4 h apart of a blood pressure measurement of ⱖ 160\110 mmHg after 20th weeks’ gestation and massive proteinuria (4 ⫹ proteins by dipstick in previously non-proteinuric women). Patients of the two groups were compared for age, parity, gestational age, birth weight and seasonal variation. The weather in eastern Sudan consists of long dry summers from March to mid-July and mild winters from October to February, separated by autumn, but this varies from area to area, since Sudan is such a large country. The maximum temperature occurs during summer and can reach 42.9°C, while the average temperature during winter is 15.9°C. Data were entered into a computer database, with SPSS software (SPSS Inc., Chicago, IL, version 16.0) and double-checked before analysis. Proportions for the seasonal deliveries were compared between the groups of the study, using the χ2-test. Univariate and multivariate analyses were also performed. Hypertensive disorder was the dependent variable and seasonal variations were the independent variables. Confidence intervals of 95% were calculated and p ⬍ 0.05 was considered significant. In case of discrepancy between the results of the χ2-test and the results of the multivariate analyses, the latter was taken as final. The study received ethical clearance from the Research Board at the Health Research Board Committee at the Ministry of Health, Kassala, Sudan.
Results Methods The medical files of women attending at Kassala hospital, eastern Sudan, with hypertension, with or without proteinuria, during the 3-year period between January 2008 and December 2010, were retrospectively retrieved. The data of patients with hyper-
During the study period, there were 9,578 deliveries; 153 patients had complications of hypertensive disorders of pregnancy, yielding an incidence rate of 1.6%. Out of these 153 cases, 97 (63.4%) had pre-eclampsia-eclampsia; 40 (26.2%) gestational hypertension; 10 (6.5%) pre-eclampsia superimposed upon
Correspondence: A. A. Ali, P.O. Box 496, Department of Obstetrics and Gynecology, Faculty of Medicine, Kassala University, Kassala, Sudan. E-mail: [email protected]
154
A. A. Ali et al.
Table I. The frequency of hypertensive disorders of pregnancy according to the seasons and months in eastern Sudan 2008–10. Cases (n ⫽ 153)
J Obstet Gynaecol Downloaded from informahealthcare.com by Dalhousie University on 04/13/15 For personal use only.
Season Winter October November December January February Summer March April May June Autumn July August September
Controls (n ⫽ 153)
n
(%)
n
(%)
p value
103 4 8 29 42 20 27 8 11 8 00 23 4 9 10
67.3 2.6 5.2 18.9 27.5 13.1 17.6 5.2 7.2 5.2 0 15 2.6 5.8 6.6
80 5 7 21 28 19 57 15 25 17 00 16 3 7 6
52.3 3.3 4.5 13.7 18.3 12.4 37.3 9.9 16.3 11.1 0 10.4 1.9 4.6 3.9
0.001
0.001
0.198
chronic hypertension; and six (3.9%) chronic hypertension. Of all cases, two-thirds were delivered purely for pre-eclampsia\ eclampsia by different methods of induction of labour or caesarean section, while one-third were reported only during labour. The mean (SD) age, parity, gestational age and birth weight at delivery of cases and controls was: 27.4 (6.2); 2.6 (1.7); 37.7 (1.5); and 2.9 (0.8) vs 26.7 (6.4); 2.7 (1.7); 39.4 (1.4); and 3.4 (0.6), respectively. Among the total cases, the range of the reported gestational age at delivery was 28–32; 32–34; 37–40; and 40–41 weeks in 3 (2%); 7 (4.6%); 6 (3.9%); 133 (86.9%); and 4 (2.6%), respectively. Of all cases and controls (306), there were 183 (59.8%) deliveries in winter; 84 (27.5%) in summer; and 39 (12.7%) in autumn. The highest rate of the disorder was in winter (103/9,578, 1.1%; CI ⫽ 1.1–2.7, OR ⫽ 1.7, p ⫽ 0.004) and the lowest rate was in autumn (23/9,578, 0.2%; CI ⫽ 0.4–1.8, OR ⫽ 0.8, p ⫽ 0.758). Our study revealed a significant association between the incidence of hypertensive disorders of pregnancy and the winter season (see Tables I and II).
tive against eclampsia (Granger et al. 2001). There are increases in the onset of pre-eclampsia during cold seasons in non-tropical climates and rainy seasons in tropical ones, such as India and Mumbai (Khojasteh et al. 2012). In the State of Texas, USA, Wellington and Mulla (2012) found a slightly increased incidence of hypertensive disorders in women delivering in winter compared with autumn. In agreement with our findings, a study from Zimbabwe concluded that the seasons have an affect on the onset of pre-eclampsia (Chiwora et al. 1998). Similarly, a study from Sweden showed that the incidence of eclampsia was nearly double during the winter months, when compared with the rest of seasons (Rylander and Lindqvist 2011) but in contrast to our study, some researchers reported no statistical correlation between pre-eclampsia and meteorological factors (Soroori et al. 2007). Phillips et al. (2004) identified seasonal correlation between pre-eclampsia and the timing of conception, rather than timing of delivery. Of course, the inconsistency of some studies might be due to other factors, such as nutrition and other risk factors for pre-eclampsia. Low vitamin D status, for example has been increasingly associated with a wide range of health problems, including pre-eclampsia; however, the evidence is inconclusive at present. Low status is particularly likely during the winter months because of the effect of the sunlight. In Sudan, nutritional deficiency and dark skin might be contributing factors for low vitamin D and have an additive role in the onset of pre-eclampsia during winter. Thus in conclusion, more attention made to hypertensive disorders of pregnancy during the winter season might reduce the morbidity and mortality related to hypertensive disorders in eastern Sudan. One limitation of this paper is the onset of pre-eclampsia and the other sub-categories of hypertensive disorders of pregnancy were considered at time of delivery, rather than conception, therefore further research is needed to consider the correlation between pre-eclampsia and time of conception. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
References
Discussion The main finding of this paper is the significant increase in hypertensive disorders of pregnancy in the winter season. Pre-eclampsia and gestational hypertension are major obstetric complications with unclear aetiology. One of the suggested hypotheses for the occurrence of pre-eclampsia is the role of environmental and nutritional factors (Soroori et al. 2007). During the various seasons, there is a wide variation in the nutrients taken by the people; moreover, cold weather could lead to vasospasm and subsequent ischaemia that is part of pathogenesis of pre-eclampsia (Granger et al. 2001). In patients primed with pre-eclampsia, many studies suggested that lower temperature is a triggering factor for eclampsia. Water loss in the dry season also proved to be protecTable II. Hypertensive disorders of pregnancy according to the seasons in eastern Sudan 2008–10, using univariate and multivariate analyses. Univariate analyses
Multivariate analyses
Season
OR
95% CI
p value
OR
95% CI
p value
Winter Summer Autumn
1.8 0.3 1.5
1.1–2.9 0.2–0.6 0.7–2.9
0.008 0.000 0.232
1.7 0.3 0.8
1.1–2.7 0.1–0.7 0.4–1.8
0.004 0.006 0.758
OR, odds ratio; CI, confidence interval.
Ali AA, Adam I. 2011. Lack of antenatal care, education and high maternal mortality in Kassala hospital, eastern Sudan during 2005–2009. Journal of Maternal-Fetal and Neonatal Medicine 24:1077–1078. Ali AA, Okud A, Khojali A, Adam I. 2012. High incidence of obstetric complications in Kassala hospital, eastern Sudan. Journal of Obstetrics and Gynaecology 32:148–149. Chiwora FM, Fruhauf J, Sculaz M, Wacker J, Basteret G, Solomayer E et al. 1998. Seasonal change in the incidence of preeclampsia in Zimbabwe. Acta Obstetricia et Gynecologica Scandinavica 77:712–716. Granger JP, Alexander BT, Bennet WA, Khalil RA. 2001. Pathophysiology of pregnancy-induced hypertension. American Journal of Hypertension 14:178S–185S. Khojasteh F, Safarzadeh A, Burayri T. 2012. Survey of correlation between preeclampsia and season and some of its risk factors in pregnant women. Journal of Women’s Health Care 1:3. Luealon P, Phupong V. 2010. Risk factors of pre-eclampsia in Thai women. Journal of the Medical Association of Thailand 93:661–666. Phillips JK, Bernstein IM, Mongeon JA, Badger GJ. 2004. Seasonal variation in preeclampsia based on timing of conception. Obstetrics and Gynecology 104:1015–1020. Rylander A, Lindqvist PG. 2011. Eclampsia is more prevalent during the winter season in Sweden. Acta Obstetricia et Gynecologica Scandinavica 90:114–117. Soroori ZZ, Sharami SH, Faraji R. 2007. Seasonal variation of the onset of preeclampsia and eclampsia. Journal of Research in Medical Sciences 12:198–202. Wellington K, Mulla ZD. 2012. Seasonal trend in the occurrence of preeclampsia and eclampsia in Texas. American Journal of Hypertension 25:115–119.
OBSTETRICS
Seasonal variation and hypertensive disorders of pregnancy in eastern Sudan A. A. Ali1, G. K. Adam2 & T. M. Abdallah1
J Obstet Gynaecol Downloaded from informahealthcare.com by Dalhousie University on 04/13/15 For personal use only.
1Faculty of
Medicine , Kassala University, Sudan and 2Gadarif University, Gadarif, Sudan
The aim of this study was to investigate the seasonal variation and hypertensive disorders of pregnancy in eastern Sudan, in the period between January 2008 and December 2010. The medical files of women attending at Kassala hospital, eastern Sudan with hypertension, with or without proteinuria were retrospectively retrieved. The data of patients with hypertensive disorders of pregnancy were compared with a similar number of controls that were normotensive and non-proteinuric. During the study period, there were 9,578 deliveries; 153 patients had hypertensive disorders of pregnancy, yielding an incidence rate of 1.6%. Of all cases and controls (306), there were 183 (59.8%) deliveries in winter, 84 (27.5%) in summer and 39 (12.7%) in autumn. The highest rate of pre-eclampsia was in winter (1.1%) (CI ⴝ 1.1–2.7, OR ⴝ 1.7, p ⴝ 0.004) and the lowest rate was in autumn (0.2%) (CI ⴝ 0.4–1.8, OR ⴝ 0.8, p ⴝ 0.758.). Our study revealed significant association between the incidence of hypertensive disorders of pregnancy and the winter season (103 (67.3%) vs 80 (52.3%), p ⴝ 0.001). Thus, more attention in the winter season might reduce the morbidity and mortality of hypertensive disorders of pregnancy. Keywords: Hypertension, pre-eclampsia, season, Sudan
Introduction Hypertensive disorders of pregnancy remain a major cause of maternal morbidity and mortality, the aetiology is not yet clear, however many risk factors have been demonstrated, such as age, obesity and multiple pregnancy (Luealon and Phupong 2010). Maternal mortality is extremely high in Sudan, with pre-eclampsia\eclampsia accounting for 4.2% of the obstetric complications in Kassala, eastern Sudan, which represents 18.1% of the direct causes of maternal deaths (Ali et al. 2012; Ali and Adam 2011). Some studies have suggested that pre-eclampsia might be affected by seasonal variation. Thus, the current study was conducted to evaluate the association between hypertensive disorders with pregnancy and different seasons in Kassala, eastern Sudan.
tensive disorders of pregnancy were compared with a similar number of controls that were normotensive and non-proteinuric. The controls were women who delivered immediately after the index case, we did not match them for any characteristic and their pregnancy was uneventful. High blood pressure was defined as two repeat readings 4 h apart of a blood pressure measurement of ⱖ 140\90 mmHg after 20 weeks’ gestation. Proteinuria was defined as ⱖ 2 ⫹ protein by dipstick in previously non-proteinuric women. According to the US National Institutes of Health (NIH), the cases were further sub-categorised into gestational hypertension (high blood pressure without proteinuria); chronic hypertension; pre-eclampsia-eclampsia; and pre-eclampsia superimposed upon chronic hypertension. Again, according to the hospital protocol, severe cases were defined as two repeat readings 4 h apart of a blood pressure measurement of ⱖ 160\110 mmHg after 20th weeks’ gestation and massive proteinuria (4 ⫹ proteins by dipstick in previously non-proteinuric women). Patients of the two groups were compared for age, parity, gestational age, birth weight and seasonal variation. The weather in eastern Sudan consists of long dry summers from March to mid-July and mild winters from October to February, separated by autumn, but this varies from area to area, since Sudan is such a large country. The maximum temperature occurs during summer and can reach 42.9°C, while the average temperature during winter is 15.9°C. Data were entered into a computer database, with SPSS software (SPSS Inc., Chicago, IL, version 16.0) and double-checked before analysis. Proportions for the seasonal deliveries were compared between the groups of the study, using the χ2-test. Univariate and multivariate analyses were also performed. Hypertensive disorder was the dependent variable and seasonal variations were the independent variables. Confidence intervals of 95% were calculated and p ⬍ 0.05 was considered significant. In case of discrepancy between the results of the χ2-test and the results of the multivariate analyses, the latter was taken as final. The study received ethical clearance from the Research Board at the Health Research Board Committee at the Ministry of Health, Kassala, Sudan.
Results Methods The medical files of women attending at Kassala hospital, eastern Sudan, with hypertension, with or without proteinuria, during the 3-year period between January 2008 and December 2010, were retrospectively retrieved. The data of patients with hyper-
During the study period, there were 9,578 deliveries; 153 patients had complications of hypertensive disorders of pregnancy, yielding an incidence rate of 1.6%. Out of these 153 cases, 97 (63.4%) had pre-eclampsia-eclampsia; 40 (26.2%) gestational hypertension; 10 (6.5%) pre-eclampsia superimposed upon
Correspondence: A. A. Ali, P.O. Box 496, Department of Obstetrics and Gynecology, Faculty of Medicine, Kassala University, Kassala, Sudan. E-mail: [email protected]
154
A. A. Ali et al.
Table I. The frequency of hypertensive disorders of pregnancy according to the seasons and months in eastern Sudan 2008–10. Cases (n ⫽ 153)
J Obstet Gynaecol Downloaded from informahealthcare.com by Dalhousie University on 04/13/15 For personal use only.
Season Winter October November December January February Summer March April May June Autumn July August September
Controls (n ⫽ 153)
n
(%)
n
(%)
p value
103 4 8 29 42 20 27 8 11 8 00 23 4 9 10
67.3 2.6 5.2 18.9 27.5 13.1 17.6 5.2 7.2 5.2 0 15 2.6 5.8 6.6
80 5 7 21 28 19 57 15 25 17 00 16 3 7 6
52.3 3.3 4.5 13.7 18.3 12.4 37.3 9.9 16.3 11.1 0 10.4 1.9 4.6 3.9
0.001
0.001
0.198
chronic hypertension; and six (3.9%) chronic hypertension. Of all cases, two-thirds were delivered purely for pre-eclampsia\ eclampsia by different methods of induction of labour or caesarean section, while one-third were reported only during labour. The mean (SD) age, parity, gestational age and birth weight at delivery of cases and controls was: 27.4 (6.2); 2.6 (1.7); 37.7 (1.5); and 2.9 (0.8) vs 26.7 (6.4); 2.7 (1.7); 39.4 (1.4); and 3.4 (0.6), respectively. Among the total cases, the range of the reported gestational age at delivery was 28–32; 32–34; 37–40; and 40–41 weeks in 3 (2%); 7 (4.6%); 6 (3.9%); 133 (86.9%); and 4 (2.6%), respectively. Of all cases and controls (306), there were 183 (59.8%) deliveries in winter; 84 (27.5%) in summer; and 39 (12.7%) in autumn. The highest rate of the disorder was in winter (103/9,578, 1.1%; CI ⫽ 1.1–2.7, OR ⫽ 1.7, p ⫽ 0.004) and the lowest rate was in autumn (23/9,578, 0.2%; CI ⫽ 0.4–1.8, OR ⫽ 0.8, p ⫽ 0.758). Our study revealed a significant association between the incidence of hypertensive disorders of pregnancy and the winter season (see Tables I and II).
tive against eclampsia (Granger et al. 2001). There are increases in the onset of pre-eclampsia during cold seasons in non-tropical climates and rainy seasons in tropical ones, such as India and Mumbai (Khojasteh et al. 2012). In the State of Texas, USA, Wellington and Mulla (2012) found a slightly increased incidence of hypertensive disorders in women delivering in winter compared with autumn. In agreement with our findings, a study from Zimbabwe concluded that the seasons have an affect on the onset of pre-eclampsia (Chiwora et al. 1998). Similarly, a study from Sweden showed that the incidence of eclampsia was nearly double during the winter months, when compared with the rest of seasons (Rylander and Lindqvist 2011) but in contrast to our study, some researchers reported no statistical correlation between pre-eclampsia and meteorological factors (Soroori et al. 2007). Phillips et al. (2004) identified seasonal correlation between pre-eclampsia and the timing of conception, rather than timing of delivery. Of course, the inconsistency of some studies might be due to other factors, such as nutrition and other risk factors for pre-eclampsia. Low vitamin D status, for example has been increasingly associated with a wide range of health problems, including pre-eclampsia; however, the evidence is inconclusive at present. Low status is particularly likely during the winter months because of the effect of the sunlight. In Sudan, nutritional deficiency and dark skin might be contributing factors for low vitamin D and have an additive role in the onset of pre-eclampsia during winter. Thus in conclusion, more attention made to hypertensive disorders of pregnancy during the winter season might reduce the morbidity and mortality related to hypertensive disorders in eastern Sudan. One limitation of this paper is the onset of pre-eclampsia and the other sub-categories of hypertensive disorders of pregnancy were considered at time of delivery, rather than conception, therefore further research is needed to consider the correlation between pre-eclampsia and time of conception. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
References
Discussion The main finding of this paper is the significant increase in hypertensive disorders of pregnancy in the winter season. Pre-eclampsia and gestational hypertension are major obstetric complications with unclear aetiology. One of the suggested hypotheses for the occurrence of pre-eclampsia is the role of environmental and nutritional factors (Soroori et al. 2007). During the various seasons, there is a wide variation in the nutrients taken by the people; moreover, cold weather could lead to vasospasm and subsequent ischaemia that is part of pathogenesis of pre-eclampsia (Granger et al. 2001). In patients primed with pre-eclampsia, many studies suggested that lower temperature is a triggering factor for eclampsia. Water loss in the dry season also proved to be protecTable II. Hypertensive disorders of pregnancy according to the seasons in eastern Sudan 2008–10, using univariate and multivariate analyses. Univariate analyses
Multivariate analyses
Season
OR
95% CI
p value
OR
95% CI
p value
Winter Summer Autumn
1.8 0.3 1.5
1.1–2.9 0.2–0.6 0.7–2.9
0.008 0.000 0.232
1.7 0.3 0.8
1.1–2.7 0.1–0.7 0.4–1.8
0.004 0.006 0.758
OR, odds ratio; CI, confidence interval.
Ali AA, Adam I. 2011. Lack of antenatal care, education and high maternal mortality in Kassala hospital, eastern Sudan during 2005–2009. Journal of Maternal-Fetal and Neonatal Medicine 24:1077–1078. Ali AA, Okud A, Khojali A, Adam I. 2012. High incidence of obstetric complications in Kassala hospital, eastern Sudan. Journal of Obstetrics and Gynaecology 32:148–149. Chiwora FM, Fruhauf J, Sculaz M, Wacker J, Basteret G, Solomayer E et al. 1998. Seasonal change in the incidence of preeclampsia in Zimbabwe. Acta Obstetricia et Gynecologica Scandinavica 77:712–716. Granger JP, Alexander BT, Bennet WA, Khalil RA. 2001. Pathophysiology of pregnancy-induced hypertension. American Journal of Hypertension 14:178S–185S. Khojasteh F, Safarzadeh A, Burayri T. 2012. Survey of correlation between preeclampsia and season and some of its risk factors in pregnant women. Journal of Women’s Health Care 1:3. Luealon P, Phupong V. 2010. Risk factors of pre-eclampsia in Thai women. Journal of the Medical Association of Thailand 93:661–666. Phillips JK, Bernstein IM, Mongeon JA, Badger GJ. 2004. Seasonal variation in preeclampsia based on timing of conception. Obstetrics and Gynecology 104:1015–1020. Rylander A, Lindqvist PG. 2011. Eclampsia is more prevalent during the winter season in Sweden. Acta Obstetricia et Gynecologica Scandinavica 90:114–117. Soroori ZZ, Sharami SH, Faraji R. 2007. Seasonal variation of the onset of preeclampsia and eclampsia. Journal of Research in Medical Sciences 12:198–202. Wellington K, Mulla ZD. 2012. Seasonal trend in the occurrence of preeclampsia and eclampsia in Texas. American Journal of Hypertension 25:115–119.
