**1. Introduction**

#### **1.1. Definition**

Normal fertility was previously defined as the ability to conceive within 2 years of regular unprotected sexual intercourse [1, 2]. Recently, infertility has been defined as failure to con‐ ceive within 1 year of regular unprotected sexual intercourse in women less than 35 years old, or within 6 months of unprotected sexual intercourse in women older than 35 years old [2, 3].

#### **1.2. Epidemiology**

According to a World Health Organization (WHO) report, the prevalence of infertility has increased since 1990, and the most recent data from 2010 estimated the worldwide incidence of infertile couples to be approximately 48.5 million (**Figure 1**) [4]. In the United States, the

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percentage of married women aged 15–44 years old who were infertile decreased from 8.5% in 1982 (2.4 million women) to 6.0% (1.5 million) in 2006–2010 [5]. In Taiwan, the total female fertility rate decreased from 7.04 million in 1951 to 1.175 million in 2015 [6]. Taiwan has thus become one of the countries with the lowest fertility rates in the world. In China, the 1‐ and 2‐year infertility rates in newly married couples were 12.5 and 6.6%, respectively [7]. In 2004, a WHO evaluation of Demographic and Health Surveys (DHS) data estimated that more than 186 million ever‐mar‐ ried women of reproductive age were infertile, translating into one in every four couples [8].

**Figure 1.** Worldwide prevalence of primary female infertility (2010). Infertility prevalence is indexed based on the age of the female partner; age‐standardized prevalence among women aged 20–44 years old is shown here [4].

#### **1.3. Impact**

A low fertility rate results in a low birth rate and an aging country. According to the Taiwan Population Policy White Paper, the total population of Taiwan is expected to decrease after 2022 [9]. A review showed that infertility or subfertility is associated with intimate partner violence (IPV) in low‐ and middle‐income countries (LMICs) [10]. Certain fertility treatments may increase the risk of ovarian or breast cancer [11, 12], while others have poor pharmaco‐ logical efficacy in infertile women older than 40 years [13]. Around one‐fifth of all subfertile couples seeking fertility treatment have clinically significant levels of depression, anxiety, and suffering, but the effects of educational and psychological interventions on mental health outcomes and pregnancy outcomes including distress, and live birth or ongoing pregnancy rates, is unclear owing to the very low quality of evidence [14].
