Iodine deficiency in pregnancy along a concentration gradient is associated with increased severity of preeclampsia in rural Eastern Cape, South Africa

Charles Bitamazire Businge,Benjamin Longo-Mbenza,Andre Pascal Kengne

doi:10.1186/s12884-021-04356-6

Abstract

BackgroundPreeclampsia is a leading cause of maternal mortality and morbidity in South Africa. Iodine deficiency in pregnancy, which is amenable to correction through iodine supplementation, has been reported to increase the risk of preeclampsia. However, the association of iodine nutrition status with preeclampsia in South Africa has not been studied.MethodsWe enrolled 51 randomly selected normotensive pregnant controls at term together with 51 consecutively selected cases of preeclampsia and 51 cases of severe preeclampsia/eclampsia, all in the third trimester, from Mthatha Regional and Nelson Mandela Academic Hospital in the Eastern Cape Province. Urinary iodine concentration (UIC), serum thyroid-stimulating hormone (TSH), triiodothyronine (FT3), thyroxine (FT4) and thyroglobulin (Tg) levels were compared between cases and controls.ResultsThe respective chronological and gestational ages at enrolment for normotensive, preeclampsia and severe preeclampsia/eclampsia participants were: age 23, 24 and 19 years (p = 0.001), and gestational age 38, 34, and 35 weeks (p < 0.001). The median gravidity was 1 for all three groups. The median UIC, FT4, FT3 revealed a decreasing and Tg a rising trend with the severity of preeclampsia (p < 0.05). TSH had a non-significant rising trend (p > 0.05). The respective median values for normotensive, preeclampsia and severe preeclampsia/eclampsia participants were UIC 217.1, 127.7, and 98.8 μg/L; FT4 14.2, 13.7, and 12. pmol/L; FT3 4.8, 4.4, and 4.0 pmol//L; Tg 19.4, 21.4, and 32. Nine microgram per liter; TSH 2.3, 2.3, and 2.5 mIU/L. UIC < 100 μg/L, Tg > 16 μg/L and FT4 < 11.3 pmol/L were independent predictors of preeclampsia/eclampsia syndrome.ConclusionWomen with severe preeclampsia/eclampsia had significantly low UIC and high Tg, suggesting protracted inadequate iodine intake. Inadequate iodine intake during pregnancy severe enough to cause elevated Tg and FT4 deficiency was associated with an increased risk of severe preeclampsia/eclampsia.

Highlights

Preeclampsia is a leading cause of maternal mortality and morbidity in South Africa
General characteristics of the participants There was no statistical difference in BMI and gestational age at booking between the normotensive controls and cases with hypertensive diseases in pregnancy (p > 0.05, Table 1)
Iodine nutritional status of cases and controls There was no difference in the median serum creatinine of normotensive pregnant controls and participants with uncomplicated preeclampsia (56.0 and 58.0 μmol/L respectively, p = 0.507) the median serum creatinine of women with severe preeclampsia was significantly higher than normotensive pregnant controls (68.0 μmol/L, p = 0.001, Table 2), it was still within the normal third-trimester range (35.0–80.0 μmol/L) with the 75th percentile reflecting mildly elevated serum creatinine in pregnancy

Summary

Introduction

Preeclampsia is a leading cause of maternal mortality and morbidity in South Africa. Preeclampsia is a leading cause of maternal and perinatal morbidity and mortality around the world, including in South Africa [1, 2]. The foetal complications of preeclampsia arise from placenta ischaemia These include intrauterine growth restriction, intrauterine foetal death, premature birth with attendant perinatal morbidity and mortality, increased risk of metabolic. The maternal complications of preeclampsia arise from endothelial dysfunction, leading to multisystem organ dysfunction. This dysfunction includes thrombocytopenia, haemolysis, hepatocellular injury, pulmonary oedema, acute kidney failure, cerebral oedema, cerebral haemorrhage, eclamptic fits, future cardiovascular disease and maternal death [2, 3]. The increase in renal filtration of iodine secondary to the physiological increase in renal blood flow, and the progressive transfer of iodine to the foetus [13] may predispose pregnant women with low daily iodine intake to iodine deficiency disorders and incident preeclampsia

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Discussion

Conclusion