This is the first study analyzing HDU in management of severe maternal morbidity in China. In this study from a large referral center in China, the ICU admission rate decreased by 20%, whereas the severity of the cases increased after introduction of obstetric HDU. Nonetheless, the maternal mortality rate remained stable. Hypertensive disorders in pregnancy was the most common cause for ICU and HDU admission, while cardiac diseases and hemorrhage accounted for the second largest proportion in ICU and HDU cases respectively.
The research showed a rising trend of high-risk pregnancies in our population, which resulted in an increased demand for higher level of care. It is notable that, after the establishment of HDU, there was a shift of women with obstetric complications to HDU, while women with severe medical co-morbidities were still referred to ICU. The rate of HDU admission in this study was 7.1%, which was higher than the UK survey (4.2%) [8] and lower than two single center reports from India (11.1% and 11.2%) [9–10]. The variations were likely to be influenced by annual birth rate, characteristics of the population, and criteria for transferring women to ICU. Similar to the literatures [9–10], which showed the main indications for high dependency care were obstetric reasons, our research found that 46.5% of women were admitted for hypertensive disorders and 43.0% were for obstetric hemorrhage, as most women with severe obstetric complication might require close support and monitoring instead of invasive treatment such as mechanical ventilation.
A cross-sectional study performed by the World Health Organization reported that 1.0% women developed a severe maternal morbidity (SMM) outcome and the leading causes were postpartum hemorrhage (26.7%) and preeclampsia or eclampsia (25.9%) [11]. In the current study, hypertensive disorders in pregnancy accounted for 39.8% of the ICU admission and postpartum hemorrhage accounted for 12.5%. It is worth noting that there is a decreasing annual trend in both hypertensive disorders and postpartum hemorrhage. If one adds the number of parturient admitted to ICU to that of those admitted to an HDU, then the overall rate is increasing; a trend which aligns with international data. It is likely that this shift toward admission to HDUs will continue.
The present study showed a significant association between pre-eclampsia and SMM, which was similar with previous researches [12, 13]. Hatti found a dose-dependent relationship between hypertensive disorders in pregnancy and SMM, with the strongest association noted for preeclampsia with severe features (OR, 5.4; 95% CI, 3.9–7.3), followed by preeclampsia without severe features and chronic hypertension [13]. It is interesting that in this study women with preeclampsia had an even higher risk of SMM (OR,7.735; 95% CI, 6.147–9.733), while chronic hypertension was not. The reason for this disparity might be related to our referral system, where women with chronic hypertension were referred to tertiary care in early pregnancy, whereas women with pre-eclampsia were often late-referrals with delayed diagnosis and suboptimal management [14]. Management of maternal hypertension is a potentially modifiable risk factor for SMM, so earlier detection and tighter blood pressure control among hypertensive pregnant women might mitigate risk for SMM at delivery [15, 16].
Generalizability and Limitations
The findings in this paper are based on a tertiary care, university-based hospital that cares for a higher percentage of medically complicated pregnancies. The high medical acuity of this population lends itself to a close evaluation of the changes in the characteristics of ICU admissions after introduction of obstetric HDU. A major limitation of our study is that it relies a single center data. The outcomes would be fairly comparable with referral centers and may not be representative to population of our region. Therefore, it is possible that the increased trend in medical co-morbidities this study is caused by an increased number of referral and not a reflection of trend in the population.