Abnormal uterine bleeding (AUB) is a group of symptoms widely recognised as the most common reason that women of reproductive age present for gynaecological care. Although this phenomenon is probably the case in most societies, until 10 years ago, this group of symptoms was poorly defined, terminologies were confused and there was no logical classification of the underlying causes. Almost ‘everything menstrual’ seemed to be labelled rather vaguely as ‘menorrhagia’!

It is now recognised that the symptoms that comprise AUB typically manifest as disorders of menstruation that collectively lead to major societal impact. The most troublesome of these symptoms is heavy menstrual bleeding (HMB), which is commonly associated with substantial pelvic pain. Chronic HMB is a regularly recurring and expensive burden on the woman herself, her close family, her work environment and the society as a whole. It is now amply demonstrated that many of these women experience a symptom that is intermittently so severe that it merits the description ‘flooding’. These aspects are highlighted by Dr Kristen Matteson , demonstrating the value of a well-developed menstrual questionnaire to aid both clinicians and investigators in determining the impact of AUB symptoms on health-related quality of life.

Much has happened in the last decade, and a strong start has been made in describing and defining AUB symptoms, clarifying terminologies and developing a conceptually simple and logical classification of the underlying causes of AUB in non-pregnant women of reproductive age. The Menstrual Disorders Committee of the Federation Internationale de Ginecologie et Obstetrique (FIGO) has endorsed and encouraged the use of new terminologies and definitions (FIGO System#1, ) and supported the development of the detailed classification PALM-COEIN (FIGO System#2; ). These developments are comprehensively described in a very practical manner by Dr Munro in Chapter 1 of this volume .

This sound conceptual basis for understanding AUB has allowed for much greater clarity in the use of ultrasound imaging for teasing out the potential structural lesions that can cause these symptoms of bleeding and pain. High-quality ultrasound is becoming more and more important in modern gynaecology but benefits greatly from skilled interpretation . This advanced imaging is revolutionising the identification and assessment of the four key types of pelvic lesions that may cause or contribute to AUB symptoms: endometrial and cervical polyps (AUB-P), adenomyosis (AUB-A), leiomyomas (AUB-L) and endometrial hyperplasia or malignancy (AUB-M) . Steps to develop sub-classifications to better understand the different types of pelvic lesions and their impacts on symptoms and long-term outcomes are beginning to offer insights into more precise means of dealing with the lesions .

One remarkable step has been the recognition of the previously overlooked importance of iron loss and disturbed iron metabolism in women with AUB and particularly HMB . Even women with menstrual periods that are self-perceived to be ‘normal’ are at high risk of developing iron deficiency, and all women with HMB have reduced iron stores, which places them at great risk if they have an unexpectedly heavy menstrual bleed or require surgery. The principles of ‘patient blood management’ are of direct importance in these women, and the initiation of effective iron therapy ought to begin at the same time as the therapy to control the bleeding.

Hormonal management of AUB symptoms, and especially for the spectrum of causes of HMB, has now largely taken over surgery for these entities, except where lesions merit surgical removal. However, AUB secondary to uterine leiomyomata (fibroids), the most classic of female reproductive tract lesions requiring major surgery, is now amenable to medical hormonal therapy with ulipristal acetate . The levonorgestrel-releasing intrauterine system (containing 52 μg of levonorgestrel) has now taken over as the undisputed first-choice hormonal therapy for HMB, secondary to AUB-E and potentially AUB-A, C and O, although other hormonal and non-hormonal medical therapies have an important place .

There are some major differences in the way AUB symptoms may present, can be investigated and are managed in different countries and cultures, and some of these aspects are well described by Tan et al .

In this volume, we have tried to illustrate a rapidly changing scene around a range of previously ill-defined symptoms and their underlying causes. We hope that these articles by well-recognised experts will provide sound guidance for current understanding and management, with a look into the future for even better care for the many women with these symptoms who are regularly seen in our gynaecological practices.