The revision history of diagnostic name, definition, and classification of Hypertensive Disorders of Pregnancy (HDP)
Historically, until 1962 in Japan, there were several disorders grouped into complications of pregnancy such as eclampsia, gestational proteinuria/nephropathy, gestational edema, pulmonary edema, and placental abruption. In 1962, these complications were integrated into “toxemia in pregnancy”. Toxemia in pregnancy was diagnosed by the three main symptoms of hypertension, proteinuria, or edema during pregnancy. Since the 1970s, the concept that hypertension is the main symptom of that syndrome has become mainstream in Western countries, and new definitions, classifications, and diagnostic criteria have been proposed, one after another. With these changes in international trends, it also became necessary to create a new definition and classification that not only accurately reflect the condition of the disease, but are clinically applicable in Japan as well. Accordingly, the Japan Society for the Study of Hypertension in Pregnancy (JSSHP) appointed a committee to create a new definition and classification. The diagnostic name was changed to ‘pregnancy induced hypertension’ in 2004, and the new definition, classification, and diagnostic criteria were announced in 2005, after which the abbreviated name of this disease became PIH. Chronic hypertension was excluded from PIH and defined as a related disorder. The new definition and classification became common in the obstetrics general clinical practice, and the PIH Management Guidelines published in 2009 were widely distributed.
Whereas the Western countries included chronic hypertension in their revised definitions and classifications, Japan did not, which set theirs apart from the others. However, with the recent increase in pregnant women of advanced age in Japan, the proportion of pregnancies complicated by hypertension has increased, and pre-pregnancy hypertension can no longer be ignored. One difficulty involves distinguishing the presence and absence of pre-pregnancy hypertension after conception. Thus, it was considered practical to use definitions including hypertension. Furthermore, given the increase in medical expenses and medical care demands from the Japanese society, new diagnostic criteria for analyzing and researching the pathogenesis and pathology of HDP are likely needed, which take into consideration the risk of maternal stroke accompanied by severe hypertension and long-term maternal and child prognosis. The diagnostic name of ‘pregnancy induced hypertension (PIH)’ became an uncommon term. Given that the Japanese definition and classification do not reflect international trends, the English notation of the diagnostic name was changed to ‘Hypertensive Disorders of Pregnancy (HDP)’ in 2016. Revisions of the definition and clinical classifications are currently underway, and should be finalized by 2018.
Revision plan for the definition, clinical classification, and diagnostic criteria of HDP
The revised draft presented by the JSSHP is currently being discussed with the Japan Society of Obstetrics and Gynecology and Japan Association of Obstetricians and Gynecologists. Major changes of the new classification are as follows:
(1) HDP is defined as hypertension in pregnancy.
(2) Eclampsia is removed from the major classification.
(3) Chronic hypertension is added to the major classification.
(4) If pregnant women with new onset of hypertension have either maternal organ dysfunction or uteroplacental dysfunction, they should be diagnosed with preeclampsia, even in the absence of proteinuria.
(5) The severity classification should be ‘severe’ when hypertension is severe, or when hypertension is mild but there is maternal organ dysfunction or uterine placental dysfunction. The term ‘mild’ is excluded from the criteria of HDP because it can be misinterpreted to mean ‘not at high risk’.
(6) The definition of ‘early onset type’ is that which appears earlier than 34 weeks gestation, in accordance with international standards.
Based on these major changes, the definition, clinical classification, and diagnostic criteria are thought to conform very closely to international standards.
