Cesarean delivery in preeclampsia and seasonal variation in a tropical rainforest beltUV Okafor1, HU Ezegwui2
1 Department of Anesthesia, University of Nigeria Teaching Hospital (Unth), Ituku Ozalla, Enugu, Nigeria
2 Department of Obstetrics and Gynecology, University of Nigeria Teaching Hospital (Unth), Ituku Ozalla, Enugu, Nigeria
Background: The pathogenesis of preeclampsia is poorly understood and recent evidence suggests that the incidence varies depending upon the season. Aim: This study was carried out to determine whether there is a seasonal variation in the presentation of preeclamptics undergoing cesarean delivery in a tropical rainforest belt. Setting: A university teaching hospital. Study Design: Retrospective. Materials and Methods: The hospital records of consecutive patients (July 1996-June 2006) with preeclampsia, who underwent cesarean delivery in a tertiary care centre, were reviewed. Data collected included patient demographics, total number of deliveries, number of cesarean deliveries, and number of preeclampsia patients and time of presentation for cesarean section. Approval of the local ethical committee was obtained. Statistical Analysis: The EPI info software program was used for statistical analysis. Results: A total of 6798 deliveries were recorded during the study period resulting in 6485 live births. There were 1579 cesarean deliveries during the period. Of these, 196 patients had toxemia of pregnancy (166 with preeclampsia and 30 with eclampsia). One hundred and forty-one patients (9% of cesarean deliveries) had cesarean delivery during the rainy season and 55 (3.5%) during the dry season (P<0.05). Amongst preeclampsia patients, 115 presented (7%) during the rainy season and 51 (3.2%) during the dry season (P<0.05). In the eclampsia group, 26 (1.65% of cesarean sections) presented during the rainy season and four (0.25%) during the dry season (P<0.05). Conclusions: There was a seasonal variation in the cesarean delivery required for preeclampsia/eclampsia patients. This may help in counseling women on when to plan their pregnancy in order to reduce the morbidity and mortality associated with this apparent seasonal disease.
Keywords: Cesarean delivery, eclampsia, preeclampsia, rainy and dry seasons, tropical climate
Preeclampsia, a multisystem disorder unique to human pregnancy is defined as the association of pregnancy-induced hypertension with proteinuria of greater than or equal to 300 mg/24 h after 20 weeks of gestation.  It is a severe complication of pregnancy leading to maternal and fetal morbidity and mortality and has been reported to complicate 4-7% of all pregnancies, , Major maternal complications of preeclampsia include placental abruption; HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) and eclampsia which can seriously endanger maternal wellbeing. ,
The pathogenesis of preeclampsia is poorly understood.  The role of seasonal variation in its etiology is one of the factors being considered. ,,,
Nigeria has two distinct climatic zones: the equatorial maritime air mass influences the climate along the coast, which is characterized by high humidity and rainfall. Further north, the tropical continental air mass brings dry dusty winds (harmattan) from the Sahara.
A spate of recent literature highlights a possible relationship between preeclampsia and the seasons. ,, This retrospective survey seeks to establish whether that pattern exists for parturients with preeclampsia presenting for cesarean delivery in Enugu, Southern Nigeria.
This retrospective review of preeclampsia and eclampsia patients who underwent cesarean section during the rainy and dry seasons, from July 1996 to June 2006 was carried out at our centre in southeast Nigeria. In our centre, the obstetric theatre and labor ward records include patients' demographics, dates and time, parity, gestational age, indications for surgery, apgar score (one and five min scores), birth weight (including placenta weight), incision-to-delivery time, anesthetic technique, names of anesthetists/obstetricians/scrub nurses, major intraoperative complications and feto-maternal outcome. This includes transfer of mothers and babies to special care units. This helps in audits where some patient folders may be unavailable. The obstetric theatre records were reviewed to identify preeclampsia/eclampsia patients who underwent cesarean section during the study period. The hospital records of these patients were examined for demographics, dates of cesarean delivery, obstetric and anesthetic records to determine whether there was a statistically significant difference in the numbers presenting during the rainy and dry seasons.
In our centre, a parturient has mild preeclampsia when she presents with the following: a blood pressure of 140/90 mmHg on two occasions 6 h or more apart, or a rise of 30 mmHg systolic or 15 mmHg diastolic from mid-trimester values; proteinuria above (+) on two consecutive urine specimens and significant non-dependent edema. A patient is labeled to have severe preeclampsia if the blood pressure is persistently above 160/110 mmHg and proteinuria above 5g/24 h (+++) and if patient has symptoms of headache, blurring of vision, epigastric pain and oliguria.The delivery services are manned by 50 registrars and senior registrars under the supervision of six consultant anesthetists, 14 consultant obstetricians and 15 consultant pediatricians. These are rostered in units to cover the delivery suite. A senior registrar should have had at least 24 months of postgraduate training including a pass in the part on fellowship examination of a postgraduate college (Nigerian or West African postgraduate medical colleges or equivalent). They are also supposed to be well-versed in the management of preeclampsia/eclampsia. There are also trained midwives covering the delivery suite in rotation.
The rainy season runs from April (average rainfall 147 mm) to October with an average rainfall of 211 mm. The dry season extends from November to March (average rainfall 35-81 mm). The hospital records of these patients were examined for demographics, dates of cesarean delivery, obstetric and anesthetic records to determine whether there was a statistically significant difference in the numbers presenting during the rainy and dry seasons.
The code and indexing system was also used to determine the number of patients with preeclampsia, who presented to the hospital during the study period. The EPI info software program was used for statistical analysis. This was based on a power of 80%, a confidence limit of 95%, prevalence of preeclampsia/eclampsia of 4% in this study. Approval of the local ethical committee was obtained.
During the study period, 6798 deliveries were conducted and 6485 live births were delivered. There were a total of 1579 cesarean deliveries (CD). Of these, 196 were carried out in those with toxemia of pregnancy (166 patients had preeclampsia, while 30 had eclampsia). One hundred and forty-one of these patients (9% of cesarean deliveries) had cesarean delivery during the rainy season and 55 patients had cesarean section (3.5% of cesarean deliveries) during the dry season (P<0.05). [Table 1] shows the meteorological data for Enugu, southeast Nigeria and [Table 2] shows the monthly presentation of the patients during the seasons.
Amongst patients with preeclampsia, 115 had CD (7% of cesarean deliveries) during the rainy season, and 51 (3.2%) during the dry season (P<0.05). Among the eclamptics, 26 (1.65% of CD) presented during the rainy season and four (0.25% of CD) during the dry season (P<0.05). On the whole, 196 out of a total of 285 preeclamptics (P<0.05) had abdominal delivery in the hospital during the study period with a 68% cesarean section rate.
In this study, a systemic seasonal variability in the need for cesarean delivery for preeclamptics was found with a peak during the rainy season and a minimum during the dry season. Literature on the seasonal variation in the incidence of preeclampsia/eclampsia is inconclusive. ,,,, However, recent literature seems to be leaning to a seasonal variation. ,, Since the etiological factors in preeclampsia are unclear, an understanding of seasonal variation in the presentation of preeclampsia may help in finding out the factors that may be involved in triggering these events. It will also help in counseling women on when to plan their pregnancy to reduce the morbidity and mortality associated with the seasonal disease.
In a study from Ghana, with almost the same climatic conditions as southern Nigeria, more cases of eclampsia were noted during the rainy season.  In Kuwait, the incidence of preeclampsia was highest in the months with high humidity and low temperature.  In the Scandinavian country of Sweden, a study of 10,666 women showed that there was a reduced incidence of preeclampsia in summer compared with the winter period.  A recent study from South Africa revealed that preeclampsia occurred more frequently in winter, similar to another study from Norway.  Though a few studies from the United States of America , concluded that the incidence of preeclampsia/eclampsia was not influenced by climatic factors even in periods of high humidity, a majority of the studies agree that preeclampsia/eclampsia occurs more in winter. ,,,,,,, A study in the tropical climate of Mumbai, India, showed that while the incidence of eclampsia was significantly higher in the rainy season, the same effect was not seen in preeclampsia, there just being a marginal increase. 
Drawing conclusions from this study may not be fortuitous considering that the study population is statistically significant if random sampling of the total hospital preeclamptic population (285) was used (P<0.05). It is also important to know the incidence of preeclamptics having cesarean delivery during different seasons as that may give a clue as to the severity of illness during the rainy and dry seasons. This is because the most expedient mode of delivery in severe preeclampsia in most developing countries may be a cesarean section. A previous study in the savannah belt region of North Central Nigeria showed increased admission of eclamptics to the intensive care unit during the rainy season. 
Interestingly, there were no seasonal variations in other indications for cesarean delivery, even in patients with placenta praevia and abruptio placenta. While controversies may continue as to the relationship between preeclampsia and the seasons, it would be interesting to see other studies on the number of preeclamptics requiring abdominal delivery during different seasons from other tropical rainforest belts.
We thank the records department of UNTH, Enugu for their help in this study, and Miss M Nwodo for graciously typing the manuscript.
[Table 1], [Table 2]