Seasonal variation in the incidence of preeclampsia and eclampsia in tropical climatic conditions

Vidya Subramaniam

doi:10.1186/1472-6874-7-18

Abstract

BackgroundObservational studies have demonstrated various correlations between hypertensive disorders of pregnancy and different weather parameters. We aim to study if a correlation exists between the incidence of eclampsia and pre-eclampsia and various weather parameters in the tropical coastal city of Mumbai which has the distinction of having relatively uniform meteorological variables all throughout the year, except for the monsoon season.MethodsWe retrospectively analysed data from a large maternity centre in Mumbai, India over a period of 36 months from March 1993 to February 1996, recording the incidence of preeclampsia and eclampsia. Meteorological data was acquired from the regional meteorological centre recording the monthly average temperature, humidity, barometric pressure and rainfall during the study period. Study period was then divided into two climate conditions: monsoon season (June to August) and dry season September to May. The incidence of preeclampsia and eclampsia and the meteorological differences between the two seasons were compared.ResultsOver a 36-month period, a total of 29562 deliveries were recorded, of which 1238 patients developed preeclampsia (4.18%) and 34 developed eclampsia (0.11%). The incidence of preeclampsia did not differ between the monsoon and the dry season (4.3% vs. 4.15%, p = 0.5). The incidence of eclampsia was significantly higher in the monsoon (0.2% vs. 0.08%, p = 0.01). The monsoon was significantly cooler (median maximum temperature 30.7°C vs. 32.3°C, p = 0.01), more humid (median relative humidity 85% vs. 70%, p = 0.0008), and received higher rainfall (median 504.9 mm vs. 0.3 mm, p = 0.0002) than the rest of the year. The median barometric pressure (1005 mb) during the monsoon season was significantly lower than the rest of the year (1012 mb, p < 0.0001).ConclusionIn the tropical climate of Mumbai, the incidence of eclampsia is significantly higher in monsoon, when the weather is cooler and humid with a lower barometric pressure than the rest of the year. This effect is not seen with preeclampsia. This strengthens the association of low temperature and high humidity with triggering of eclampsia.

Highlights

Observational studies have demonstrated various correlations between hypertensive disorders of pregnancy and different weather parameters
The incidence of preeclampsia did not differ between the monsoon and the dry season (316/7346 in monsoon [4.3%] vs. 922/22216 in the dry season [4.15%], p = 0.5)
The incidence of eclampsia was significantly higher in the monsoon (0.2% vs. 0.08%, p = 0.01) as compared to the dry season (Table 1)

Summary

Introduction

Observational studies have demonstrated various correlations between hypertensive disorders of pregnancy and different weather parameters. Previous studies have shown a variable association of preeclampsia and eclampsia with the changing weather patterns of different seasons. Wacker and colleagues found no statistically different frequency of preeclampsia in the dry and wet seasons that occur in Zimbabwe [12]. All these studies have assessed if there was a seasonal variation in the incidence of preeclampsia. Phillips et al, in their study, have evaluated the link between the timing of conception with risk of preeclampsia [13] They found the highest risk of preeclampsia in conceptions occurring in the summer season, whereas there was no significant variation in the incidence of preeclampsia based on the timing of delivery

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