Comparison of Pregnancy Outcomes Between Chronic Hypertensive Pregnant Women With and Without Superimposed Preeclampsia at Kenyatta National Hospital From 2016-2021

Abstract

Introduction: Hypertensive disorders of pregnancy (HDPs) complicate 6-15% of pregnancies globally, and are associated with increased risks of adverse maternal and perinatal outcomes. HDPs are the 3rd leading cause of maternal mortality in Kenya. Chronic hypertension as one of the HDPs affects 3-5% of pregnancies and is gradually becoming common due to increasing incidence of obesity and delayed child bearing. Studies from high income countries have illustrated that pregnancies complicated with chronic hypertension are at a higher risk of adverse maternal and perinatal outcomes such as superimposed preeclampsia (SPE), placental abruption, fetal growth restriction, cesarean sections, preterm deliveries, low birth weight and perinatal mortality. These studies also suggest that the incidence of preeclampsia is higher in chronic hypertension than in the general population with worse obstetric outcomes. There is no study done in our region on chronic hypertension comparing the outcomes between those with and without SPE. It is therefore, not known whether the documented findings apply in low and middle income populations. This study, seeks to determine the association between chronic hypertension with or without SPE and adverse maternal and perinatal outcomes among pregnant women at Kenyatta National Hospital (KNH). Objective: To determine maternal and perinatal outcomes for women with chronic hypertension, comparing those with SPE with those without SPE at KNH between the years 2016 and 2020. Methodology: A retrospective cohort study was conducted at KNH. Patient records of pregnant women with chronic hypertension were reviewed from December 31, 2021, working backwards until the desired sample size was achieved. Adverse maternal and perinatal outcomes among those with and without SPE were compared. A total of 162 patients’ records were enrolled in the study. Eligibility was determined by the American College of Obstetrics & Gynecology criteria for diagnosis of chronic hypertension. The records were then classified into 2 equal groups: SPE group and no SPE group. Data was extracted using a structured data extraction tool and analyzed using SPSS version 26. Maternal and perinatal outcomes as well as the sociodemographic and clinical characteristics of the two groups were compared. Analysis was done using SPSS Version 26. Categorical variables were summarized as frequencies and proportions and compared using the Chi-square test and Fisher's exact test while continuous variables were summarized as means/median and standard deviations and interquartile range and compared using student-t or Mann Whitney U test as appropriate. Binary logistic regression was used to evaluate the association between exposure to chronic hypertension (with and without SPE) and the maternal, fetal, and immediate neonatal outcomes. This yielded odds ratios (OR) and corresponding 95% confidence intervals (CI) 15 Results: Of the 162 patients recruited, the mean age was 34 years, 61% were multiparous, 70% had hypertension before pregnancy, 37% had history of pre-eclampsia, and 93% were on hypertensive drugs during the pregnancy. Only 23% of the study participants were on Aspirin antenatally. Chronic hypertension with SPE was significantly associated with an adverse maternal, fetal, and early neonatal outcome with AOR of 3.81(1.85,7.84), 2.97(1.48,5.96), and 5.63(2.59,12.25) respectively. Mode of delivery and gestational age at delivery were the noteworthy adverse maternal outcomes with SPE, with primary CS being significantly more common in women with SPE (2.43(1.15,5.14)), and preterm delivery (8.74(3.70,20.64)). Adverse neonatal outcomes were significantly more common among women with SPE, including prematurity (8.74(3.70,20.64)), SGA (2.45(1.08,5.56)), LBW (4.91(2.28,10.55)) and admission to NBU/NICU (2.34(1.11,4.93)). The 2 groups were not significantly different with regard to most of their sociodemographic and clinical characteristics except parity, family planning, duration of hospital stay and antenatal BP results. Conclusion: The study contributes to the current limited local and regional data on the significance of chronic hypertension in pregnancy. There is an overall increased risk of adverse maternal and perinatal outcomes. The incidence of adverse maternal and perinatal outcomes is high with or without SPE, but worsens significantly with SPE than reported in high income countries. This indicates that we should intensify antenatal care of chronic hypertensive women locally and counsel them better on the risk of SPE on their pregnancy outcomes. Further evaluations of factors influencing the development of SPE and factors mitigating poor outcomes should be conducted with a larger multicenter study.