The main findings of the current study were as follows: 1) the MPV levels were significantly higher in patients with HTG-AP during pregnancy than the control group; 2) the mean MPV levels were increased with the severity of HTG-AP at onset; 3) the MPV levels were lower during remission than at onset in patients with hypertriglyceridemia-induced SAP during pregnancy; 4) the MPV levels were independently associated with HTG-AP during pregnancy. These results indicate that MPV could be related to HTG-AP severity and used as an independent risk factor of HTG-AP during pregnancy.
HTG-AP during pregnancy is a rare but severe disease with high maternal-fetal mortality risks, which presents as a systemic inflammatory process that is often accompanied by thrombosis and bleeding disorders. Normally, triglyceride levels rise gradually during pregnancy and reach a peak in the third trimester of gestation to 2-to-4-fold over pre-pregnancy levels. In addition, high levels of estrogen related to pregnancy can reduce the activity of lipoprotein lipase and lead to hypertriglyceridemia  There is an increased risk for AP when serum triglyceride levels are > 10 g/L (11.3 mmol/L) , which is why most cases of HTG-AP occurred during the third trimester of gestation.
Currently, there are no standardized guidelines for clinicians regarding hypertriglyceridemia-induced AP during pregnancy. Moreover, the main diagnostic methods rely on clinical experience, and the existing serum biomarkers are helpful in assessing AP severity. Therefore, early, alternative, and easily applicable markers are needed.
It has been reported that platelet activation plays an important role in the development and evolution of AP . MPV is a simple parameter showing platelet function and activation that can be measured by complete blood count analysis at no additional cost.
Abnormal MPV has been correlated with thrombotic and inflammatory conditions, such as myocardial infarction, acute cerebral ischemia, inﬂammatory bowel disease, rheumatoid arthritis, and familial Mediterranean fever [16-20]; however, the relationship between MPV and AP has not been fully clarified, especially hypertriglyceridemia-induced SAP during pregnancy.
Our finding showed that MPV levels were increased in patients with HTG-AP during pregnancy compared with controls. Furthermore, MPV levels were decreased during remission.
To date, several previous studies have investigated the relationship between AP and MPV, but the results were conﬂicting. Beyazit et al  examined the role of MPV in AP and described a significant decrease in MPV in patients with AP compared with healthy subjects. Erbis et al  in a study involving 76 patients with pancreatitis showed that patients with pancreatitis had lower levels in MPV, and the mean MPV values were lower in AP patients (7.2 ± 0.52 fL) than in AP (7.9 ± 0.53 fL). Another contemporaneous study reported that MPV was significantly lower on admission than during remission in biliary and non-biliary AP patients . Recently, Lei et al  also reported that MPV levels were significantly lower in the AP group than the control group, and MPV presented an upward trend during the first week after admission in all AP patients.
Although the previous results suggested low MPV levels in AP, these studies excluded patients who had pregnancy or hyperlipidemia. In comparison, we focused on patients with hyperlipidemia-induced AP in pregnancy. It is probable that the disparity in the studies may be explained by differences in the study population and design. Thus, we should pay more attention to further studies.
The exact reason for increased MPV in hyperlipidemia-induced SAP during pregnancy remains unknown, but it has been speculated that platelets not only control thrombosis and hemostasis, but also regulate inflammatory conditions. There is a stimulation of megakaryopoiesis in the early stages of the inflammatory process associated with hyperlipidemia-induced SAP, which produces a large amount of young and large platelets with high procoagulation potential . Osada et al  observed a significant increase in the number of large platelets in the AP groups; the median and mean MPV remained at high levels during the acute phase in the mild and severe AP groups. Moreover, the MPV levels showed a downward trend in remission phase in patients with SAP, which supported our results.
Thrombocytopenia is not only a common finding during pregnancy, but also frequent at the onset of AP . Thrombocytopenia can lead to enhanced thrombopoiesis, which increases the quantity of highly reactive large-sized platelets . Thus, these findings may partly explain why there were high MPV levels in our study patients. Akbal et al  also detected higher MPV levels in patients with AP at the time of admission than controls, which was consistent with our results. In addition, our data also showed that the D-dimer was elevated in patients with HTG-AP during pregnancy, which were in agreement with the alterations in MPV. Together, these studies suggest that an elevated MPV facilitates platelet adhesiveness and aggregation, which may lead to a high prothrombotic potential and impairment of pancreatic microcirculation in hyperlipidemia-induced SAP during pregnancy.
There were some limitations to the present study. First, the study population was relatively small. The current study had a very limited number of patients because of the rarity of HTG-AP during pregnancy. Second, owing to ethical reasons, we could not assess the clinical benefits of antiplatelet therapy in this population. It was also difficult to adjust adequately for measurement of patient adherence. Third, this was a single-center, retrospective cohort study; therefore, the results we observed cannot be evaluated definitively. Further multi-center, large-scale, prospective studies are needed to verify the findings of the present study. Although our results may be limited in terms of the sample size and study design, the present study still offers implications for the diagnosis and management of HTG-AP during pregnancy. Given the specific population, we believe our findings may provide new evidence for further studies with larger sample sizes.