CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 2, March/April 2022 AFRICA 67 Results The mean maternal age of the study group was 29.93 ± 5.71 years (18–43) and the mean gestational age was 33.72 ± 4.47 weeks (22.0–39.29). The two hypertensive groups and the controls were matched for maternal and gestational age. Between the two hypertensive groups there was no statistical difference for the prevalence of early (72.2 vs 83.8%, p = 0.269) and severe forms (36.1 vs 35.1%, p = 1.000). There was no statistical difference between the groups for women who defined themselves as smokers (44.4% in gestational hypertension, 45.9% in pre-eclampsia and 54.0% in controls; p > 0.05) and also between the current smokers who reported smoking during the pregnancy (37.5, 47.1 and 51.9%, respectively, p > 0.05). More primigravid women were in the combined hypertensive groups compared to the healthy controls (49.3 vs 24%, p = 0.008), while there was no statistical difference for women with a second (26 vs 44%, p = 0.059) and third or more pregnancies (24.7 vs 32%, p = 0.494). Women in the hypertensive groups had significantly higher pre-pregnancy body mass index (BMI) compared to the controls (28.58 ± 6.14 kg/m2 in the gestational hypertension group, 27.26 ± 5.68 kg/m2 in the pre-eclampsia group and 22.58 ± 5.11 kg/ m2 in the controls, p < 0.05), current BMI (33.66 ± 5.75, 31.77 ± 5.32 and 27.81 ± 5.49 kg/m2, respectively, p < 0,05) and body surface area (BSA) (1.97 ± 0.20, 1.96 ± 0.18 and 1.83 ± 0.20 m2, respectively, p < 0.05). Current weight gain, calculated as the difference between self-reported pre-pregnancy weight and weight measured at the time of the inclusion in the study did not differ statistically between the three groups (13.69 ± 6.54, 12.94 ± 7.51 and 14.05 ± 6.18 kg, respectively, p > 0.05). Mean interleukin-6 levels were significantly higher in the gestational hypertension group (5.08 ± 5.16 pg/ml, p = 0.020) and pre-eclampsia group (8.06 ± 12.48 pg/ml, p = 0.002) compared to the controls (2.77 ± 2.43 pg/ml), but the values did not differ significantly between the two hypertensive groups (p = 0.508) despite a tendency for higher levels in the pre-eclampsia group. When analysed according to the severity and onset of the disease, there was no statistical difference between the levels in the newly formed subgroups (Table 1). The difference between the controls and the late forms of both pathologies, as well as the mild form of gestational hypertension was non-significant (Table 2). Mean levels of interleukin-6 were significantly lower in women who were in their second pregnancy compared to those in the first pregnancy. When analysing the whole study group, women whose pregnancy was the third or more did not differ significantly from those in either first or second pregnancy. When each group was analysed separately, there was a tendency for lower interleukin-6 levels in the second pregnancy for the controls and gestational hypertension groups, while for the pre-eclampsia group, the lowest levels were in women with three or more pregnancies, but the difference was not significant (Table 3). Women who stated that they were smokers had significantly higher levels of serum interleukin-6 than non-smokers in the whole study group, as well as when separately analysing the controls, the gestational hypertension group and the combined hypertensive groups. For those who were smokers, smoking during pregnancy did not lead to significantly different levels of serum interleukin-6 in any of the groups analysed (Table 3). ROC curve analysis was used to determine the ability to differentiate between the hypertensive and normotensive pregnancies using interleukin-6 levels. The area under the curve (AUC) for differentiating between women with gestational hypertension and the controls was 0.65 at a cut-off point of 4 pg/ml (p = 0.020) (Fig. 1). The AUC for differentiating between women with pre-eclampsia and the controls was 0.70 at a cut-off point of 2.82 pg/ml (p = 0.002) (Fig. 2). The AUC for differentiating between the combined hypertensive group and the controls was 0.67 at a cut-off point of 2.5 pg/ml (p = 0.001) (Fig. 3). The respective sensitivity, specificity, positive and negative predictive values and accuracy of the cut-off values are given in Table 4. Binary logistic regression gave an odds ratio of 4.80 (95% CI: 1.90–12.13) for women with interleukin-6 levels greater than or equal to the provided cut-off points to have pre-eclampsia, and an odds ratio of 3.21 (95% CI: 1.30–7.92) for having gestational hypertension. The odds ratio for the presence of either gestational hypertension or pre-eclampsia was 3.13 (95% CI: 1.48–6.62). Correlation analysis gave positive correlations of interleukin-6 levels in the whole study group with BMI before pregnancy (r = 0.266), current BMI (r = 0.284) and BSA (r = 0.223). In the control group, all of those correlations were significant and stronger (r = 0.305; r = 0.466; r = 0.468, respectively), and also significant positive correlations with gestational age (r = 0.488) and current weight gain (r = 0.382) were present. No significant correlations existed in the gestational hypertension or pre-eclampsia groups when analysed separately. The levels did not correlate in any of the groups with maternal age, and in the hypertensive groups they did not correlate with the maximum detected systolic or diastolic blood pressure (Table 5). Using the data from the echocardiographic examination of the women, we found several correlations between interleukin-6 Table 1. Comparative analysis of interleukin-6 levels and forms of gestational hypertension and pre-eclampsia Group Early onset Late onset p-value Number Mean SD Number Mean SD GH 26 4.81 3.43 10 5.80 8.36 0.664 PE 31 6.46 7.73 6 16.34 25.78 0.888 Mild form Severe form Number Mean SD Number Mean SD GH 23 5.32 6.15 13 4.66 2.82 0.626 PE 24 8.98 15.06 13 6.37 5.26 0.604 GH: gestational hypertension; PE: pre-eclampsia; SD: standard deviation. Table 2. Comparative analysis of interleukin-6 levels between different forms of gestational hypertension and pre-eclampsia and the controls Subgroup GH + PE Controls p-value Number Mean SD Number Mean SD Early form of GH 26 4.81 3.43 50 2.77 2.43 0.019 Late form of GH 10 5.80 8.36 0.312 Mild form of GH 23 5.32 6.15 0.149 Severe form of GH 13 4.66 2.82 0.014 Early form of PE 31 6.46 7.73 0.002 Late form of PE 6 16.34 25.78 0.256 Mild form of PE 24 8.98 15.06 0.020 Severe form of PE 13 6.37 5.26 0.006 GH: gestational hypertension; PE: pre-eclampsia; SD: standard deviation.
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