The maternal mortality rate in China is 17.7 per 100,000 among pregnant women with PH in 2015 . Although the incidence of PH in pregnant women is not high, the mortality rate is relatively high [10–11]. Our previous study found that although the mortality rate was higher in patients with PH in pregnancy, the deaths were all from patients with IPAH . Therefore, a better understanding of the clinical characteristics and PAH-specific therapy of patients can provide new ideas for IPAH treatment.
IPAH is a severe and sudden disease. Most patients are healthy before the diagnosis of IPAH, and it is a short time from symptom onset to diagnosis [12, 13]. Our research shows that it only takes a few weeks or even a few days from symptom onset to diagnosis for most of these patients. However, The Third Hospital of Guangzhou Medical University is a referral center for seriously ill pregnant patients in Guangdong Province. Most IPAH patients are transferred to us after a period of untreated pulmonary arterial pressure. Most of the patients were in poor condition, which led to a short treatment period before delivery. Our study suggested that the mortality of patients was correlated with the length of treatment and the extent of the decrease in pulmonary arterial pressure before delivery. A longer treatment time and a more significant reduction in pulmonary arterial pressure can decrease mortality. Otherwise, all condition got worse in or after delivery which means prenatal period is safer. To achieve this goal, primary hospitals must understand how to treat a pregnant patient with IPAH, especially before delivery. Our study does not suggest which medication before delivery can reduce mortality, but considering the small number of cases, further study is needed.
Childbirth is one of the most challenging periods for women with PH because of the considerable changes in systemic circulation volume . In our study, 2 cases deteriorated during Delivery. One required ECPR resuscitation and died 1 day after surgery, and the other died 4 hours after surgery. According to the 4 cases with pulmonary artery systolic pressure measured by echocardiography(SPAPECHO), it can be seen that PAP dropped to the lowest value after fetal delivery and then rose rapidly. The drastic change of pulmonary arterial pressure made the patient get a right heart failure which led to death. Therefore, reducing and stabilizing pulmonary arterial pressure is an important step to prevent the death of patients with right heart failure. First, as mentioned above, there should be sufficient prenatal treatment time to reduce the patient's pulmonary arterial pressure and reduce the patient's circulation volume before the birth to reduce the fluctuation; Second, SPAPECHO and proper ventricular function during labor, and the use of drugs to reduce PAP when necessary, which can also prevent death from right heart failure.
However, PH is a disease with significant risk and high mortality. Even in developed countries such as the United States and Japan, there is still a high mortality rate . While the mortality rate of pregnancy patients with PH has been improved, but it is still not low [16, 17]. ECMO can replace patients' cardiopulmonary function and prevent pregnant patients from sudden death during surgery and postpartum. It plays an essential role in the treatment of pregnant women with PH . Our study showed that 1 patient treated with VA-ECMO was survived, and 2 patients treated with ECPR died. This is in line with ELSO's date that the success rate of VA-ECMO is much higher than that of ECPR[19, 20]. However, we noted that the two patients who died did not have enough time to control the PAP before delivery due to various reasons, so the right heart failure came quickly and sharply during cesarean section or postpartum, and only ECPR treatment was available. How to evaluate unprepared patients' proper heart function? How to choose the timing of ECMO treatment? How to prepare for ECMO treatment? Or whether ECMO treatment can be performed in advance? We believe that further research is needed in this area.
The application of oxytocin in cesarean section in pregnancy patients with PAH is controversial. Studies have suggested that oxytocin can worsen the decrease of proper coronary artery blood flow in patients with PH, leading to right ventricular failure [21–23]. Our study found that although one patient underwent ECPR for cardiac and respiratory arrest following the intraoperative use of oxytocin, overall patient mortality was not associated with intraoperative use of oxytocin. Compared with other studies, we used oxytocin as an intramuscular or intravenous infusion. Perhaps the slower onset time had less effect on proper heart function, which is why oxytocin did not increase mortality in these patients. However, given our small number of cases, further study is needed to determine whether intramuscular or intravenous administration of oxytocin impacts maternal mortality with PH.
The PAP of patients after delivery did not significantly decrease compared with that before delivery, 2 cases of ECMO treatment were applied after delivery, and all the patients who died after delivery, which once again confirmed that IPAH patients are still at the highest risk of death within 1 week after delivery [24, 25]. The survival rate of patients who received treprostinil was higher than those who did not, suggesting the importance of strict control of PAH and the need for intravenous medication (faster onset) after delivery. However, the ICU time of postpartum patients is very long, so how to more rationally control patients' PAH, thus reducing their hospitalization and ICU time, need a further study.