Serum relaxin in preeclamptic and normotensive pregnant women at the Lagos University Teaching Hospital

Background: Preeclampsia is a pregnancy-specific multi-systemic progressive disorder that is unique to human pregnancy occurring in the second half of pregnancy. Reliable biochemical markers for prediction, diagnosis and management of preeclampsia would have a great impact on maternal health and several of these markers have been suggested. Relaxin is a peptide that has shown promising effect in the treatment of cardiovascular diseases and it is believed to increase vascular endothelial growth factor and placenta growth factor both of which promote angiogenesis and placentation in pregnancy. Thus, relaxin may play an important regulatory role in maternal vascular adaptations during pregnancy. Aim: This study therefore aimed to find out the difference, if any, in serum relaxin levels in preeclamptic and normotensive pregnant women at Lagos University Teaching Hospital. Methods: This was an analytical comparative cross-sectional study involving pregnant women with preeclampsia (study group- 48 had mild preeclampsia while 42 had severe preeclampsia) and age-, parity- and gestational age-matched women without preeclampsia (comparative group). Venous samples were collected from eligible participants after counselling and obtaining informed consent. Serum relaxin was determined using the Quantikine Human Relaxin-2 Immunoassay according to manufacturer’s instructions. A structured questionnaire was also administered to collect relevant sociodemographic and clinical information. Data were entered and analyzed using the IBM Statistical Package for Social Sciences (SPSS Statistics) Version 23. Armonk, NY: IBM Corp. Categorical variables were summarized and presented as frequency and percentages. The test of normality of continuous variables was performed using the Kolmogorov-Smirnov test. The continuous variables such as age that were normally distributed were presented as mean (± standard deviation). All tests were two- tailed and statistical significances was set at p < 0.05. Results: The mean level of serum relaxin in women with preeclampsia was significantly lower than that of the normotensive women (0.24+0.03ng/ml vs. 0.42±0.05ng/ml; p < 0.001). However, there was no significant difference in the mean serum relaxin levels in participants with mild preeclampsia when compared to those with severe preeclampsia (0.24 + 0.02ng/ml vs. 0.23ng/ml + 0.01; p = 0.271). Conclusion: Women with pre-eclampsia have significantly lower levels of serum relaxin than normotensive pregnant women. However, there is no significant difference in mean serum relaxin levels in women with mild when compared to those with severe preeclampsia. Therefore, development of pre-eclampsia is associated with lower serum levels of relaxin, though the relaxin levels may not indicate the severity of disease.