In recent years, the mortality rate among pregnant women with PH has been considerably high, at approximately 25% [4, 5]. Even in patients who receive targeted therapy against PH, the mortality rate is still approximately 16% [4, 5]. Moreover, the mortality rate in pregnant women with severe PH who develop Eisenmenger syndrome is very high, ranging from 40–50% in one study  and 23% in another . PH during pregnancy is reported to worsen between the 20th and 24th weeks of gestation ; the mortality rate is the highest during puerperium, the week immediately following delivery [4, 8].
During pregnancy, the circulating plasma volume increases and is approximately 50% greater than that in the non-pregnant state . Additionally, in pregnancy, cardiac output is 30–50% higher , and systemic vascular resistance is reduced by up to 40% due to the vasodilating effects of estrogen and progesterone and the formation of the placental circulation . However, in pregnant women with PH, pulmonary vasodilatory capacity is reduced ; therefore, mean PAP and pulmonary vascular resistance (PVR) increase significantly. Consequently, the right ventricle cannot handle the afterload, resulting in right heart failure.
A pregnant woman with PH may become hypoxemic, which may affect fetal development. In Eisenmenger syndrome, preterm labor (50–64%) and fetal growth failure (37–50%) are highly prevalent [13, 14]. In the current case, the birth weight of the newborn was 1880 g (-1.7 SD), which is low for her gestational age.
Patients with PH are generally advised not to get pregnant. However, there are cases when the disease becomes apparent only during the pregnancy, such as the discovery of a left-right shunt due to an ASD. Even when the disease severity is high, the pregnancy and childbirth are often completed without any major complications. Additionally, the probability of complications from PH is low, i.e., less than 10% . In the current case, the patient did not experience complications until her third pregnancy. The previous two deliveries were asymptomatic, and ASD was not detected. However, as per electrocardiogram findings, she had some strain in the right side of her heart at the time of her first delivery. This suggests that pulmonary artery remodeling due to PH may have occurred during the first pregnancy. The shunt blood flow may have increased after two pregnancies, and this pregnancy may have pushed the symptoms further.
The optimal timing of delivery in pregnant women with PH is still uncertain; therefore, it is important to weigh the risk of continuing the pregnancy against the risk of premature birth of the newborn. If a pregnant woman with PH is stable, planned delivery at 34–36 weeks is recommended; however, if a patient is unstable, the baby should be delivered at 32–34 weeks [16, 17]. The method of delivery needs to be evaluated on a case-by-case basis. Although vaginal delivery is not contraindicated with Eisenmenger syndrome, early cesarean section is recommended in cases with deterioration of maternal or fetal health .
In vaginal delivery, frequent use of the Valsalva maneuver may decrease venous perfusion due to increased intrathoracic pressure. Additionally, decreased venous perfusion due to vagal reflex caused by labor pain and increased heart rate due to sympathetic nervous system stimulation may lead to labor-induced acidosis, hypercarbonate plasma, hypoxemia, and increased pulmonary artery pressure. Effective epidural analgesia should be used . After delivery, there may be rapid autotransfusion from the uterus and increased venous perfusion due to the release of inferior vena cava obstruction. Therefore, vaginal delivery is hemodynamically unstable and requires careful blood pressure control. In addition, oxytocin can cause hypotension and tachycardia; therefore, it should be administered slowly . In pregnant women with PH, the possibility of preterm labor is high due to deterioration of maternal hemodynamics; therefore, cesarean section is often the choice.
In elective cesarean delivery, pregnant women with PH can avoid labor pain and autotransfusion associated with uterine contractions. The cesarean section is performed under anesthesia with hemodynamic optimization . During cesarean section in PH patients, general anesthesia further increases PVR via positive-pressure ventilation and PAP via tracheal intubation. Intra-aortic pressure and ventilation volume should be controlled at a low level. To avoid the above risks, epidural anesthesia or a combination of spinal subarachnoid anesthesia and epidural anesthesia is preferable .
In the current case, the patient was multigravida, cervical ripening was observed, and the delivery time was expected to be short. The possibility of vaginal delivery was discussed, due to the advantage of avoiding bleeding risks. However, cesarean section was selected as invasive monitoring was difficult in the delivery room and the patient’s condition was worsening. In addition, general anesthesia was chosen over epidural and spinal subarachnoid anesthesia to allow swift initiation of percutaneous cardiopulmonary support system during the cesarean section.
After delivery, a rapid increase in circulating plasma volume via autotransfusion due to uterine recovery and migration of peripheral edema into the vascular system can cause sudden death in mothers with PH . Additionally, these women are at a higher risk of thrombosis . Therefore, treatment with pulmonary vasodilators and anticoagulation therapy is imperative after delivery [7, 20]. In the current case, NO was administered both before and immediately after the delivery. In addition, the patient was treated with a multidrug combination of PGI2 and PDE5 inhibitors and ET receptor antagonists. Intravenous administration of PGI2 should be performed cautiously to prevent the risk of infection . ET receptor antagonists are limited to postpartum use because of their known teratogenicity . In the present case, the mother had no hope to get pregnant again; therefore, we used ET receptor antagonists for her treatment.
In recent years, "Treat and Repair" strategy, in which PH is controlled by the abovementioned PH-specific medications followed by transcatheter shunt closure, has been attracting attention for PH caused by shunt disease . This strategy is also mentioned in the 2020 adult congenital heart disease guidelines  and was applied to to the present case. However, there is no clear evidence on the severity of the disease and the long-term prognosis of treat and repair, and further data analysis is needed.