Should men and women be encouraged to start childbearing at a younger age?

In the developed part of the world, many couples are postponing childbearing ([1] for European countries; [2] for Canada; [3] for the USA). In many countries, a women’s average age at first childbirth is approximately 28–30 years. The trend towards delayed childbearing is most pronounced among educated women. Surveys among childless male and female university students demonstrate that more than 90% want to have children in the future [4–7].

Advanced female & male age

Advanced age reduces fecundity – expressed as the ability for women to give birth to children [8]. Larsen and Yan calculated the monthly probability of having a live-born child based on data from a population not using fertility control [9]. The monthly rate was 24% among 25-year-old women, but decreased to 12% at the age of 35 years, and to 7% at the age of 40 years. In addition, advanced male age has been found to be an independent risk factor for prolonged time to births. Based on a large cohort study of couples having achieved a live birth, Ford et al. demonstrated that the odds ratio for a conception in less than 12 months leading to a birth decreased by 3% per year of increasing male age [10]. Infertility, defined as not achieving a pregnancy after trying for more than 12 months, increases with advanced age, and so does the risk of spontaneous abortions [11]. Dunson et al. showed that the 12-month infertility prevalence was 18% among couples where both the woman and the male partner were 35 years old [12]. The infertility prevalence increased to 28% when the male partner was 40 years old and the woman 35 years old. In conclusion, the postponement of childbearing until the mid-30s or later increases the proportion of couples having fertility problems, increases the risk of becoming a fertility patient, and increases the risk of staying childless or having fewer children than desired.

Leridon and Slama calculated the impact of women postponing their first pregnancy attempt by 2.5 years, from 25.1 to 27.6 years [13]. The consequences were that the proportion of involuntarily childless couples increased by 30.6%, from 9.8 to 12.8%, and the proportion of couples with fewer births than desired increased by 25.0%, from 14.8 to 18.5%. If the postponement of mean age of first pregnancy attempt was increased by nearly 6 years to age 30.8 years, which is close to the current fertility pattern in many countries, the proportion of involuntarily childless couples increased to 15.8%, and the proportion of couples with fewer births than desired increased to 24.0%.

Across European countries, the number of couples receiving fertility treatment is increasing [14]. However, assisted reproduction treatment cannot compensate for the age-related decline in fecundity. In a complete 5-year follow-up of 1338 couples having initiated fertility treatment, 74.9% of the women under 35 years of age achieved a live birth, compared with 52.2% among women over 35 years of age [15]. Leridon estimated that assisted reproduction technology compensates for only half of the births lost by postponing a first attempt of pregnancy from age 30 to 35 years [11]. If the first pregnancy attempt is postponed from 35 to 40 years, assisted reproduction technology compensates for fewer than 30% of the births lost by the postponement.

The fertility awareness of populations

Although only a few fertility-awareness studies have been conducted thus far, it appears that neither young women nor young men are sufficiently aware of the age-related increased risk of infertility, of staying involuntarily childless or of not having as many children as desired. Fertility awareness studies among university students have shown how young women and men markedly overestimated the women’s fecundity according to age and the couple’s cumulative fecundity after 1 year of unprotected intercourse [4,6]. Furthermore, the participants overestimated the chances of having a child after IVF treatment. Young female university students were more concerned about smoking, alcohol and psychological stress as risk factors of infertility (33–46% of the participants), and only 17% mentioned female age as a risk factor [6]. Bunting and Boivin reported that a cohort of female and male university students from the UK were aware of the impact of negative lifestyle factors on fertility, but falsely believed in fertility myths; that is, a positive effect of healthy habits on fertility [16]. Tough et al. investigated a group of 20–45-year-old childless women and men [17]. Over half of the respondents were aware of the fact that women over the age of 35 years were more likely to experience difficulties in conceiving. Less than half of the participants knew that advanced maternal age increased the risk of stillbirth, multiple birth and preterm delivery [17]. Maheshwari et al. studied fertility awareness among already pregnant women and women attending a fertility clinic [18]. Most of these women were aware that age could affect their chances of pregnancy. However, 59% of the women were not aware that the chance of having a baby after IVF decreased between female ages of 30 and 40 years, and approximately 80% of the participants believed that fertility treatment could overcome such an age-related decline in fecundity [18].

Apart from advanced age, there are other important risk factors for infertility, such as female and male obesity [19,20], active and passive smoking [21,22], sexually transmitted diseases [23] and reproductive toxic substances at work places [24], and possibly in the environment [25].

Need for action

There is a need for initiating several different action strategies:

• • It is of paramount importance for health professionals to reduce the knowledge gap between the generally limited recognition on one side of risk factors of infertility and involuntarily childlessness, and on the other side the available documentation that advanced age, as well as other factors, are important infertility risk factors. Furthermore, we, as assisted reproduction technology professionals, must get the message across that assisted reproduction technology can not compensate for the age-related decline in fecundity, and raise awareness of increased pregnancy complications and increased risk of adverse pregnancy outcome among older couples. Increasing the fertility awareness of populations is important in order for individuals to be able to make an informed decision regarding the timing of parenthood. Postponing childbearing to the mid-30s or later without realizing how advanced age is linked to infertility increases the risk of even more people becoming involuntarily childless in the future;

• • It is of great importance that the inclusion of young men into the agenda of fertility awareness and decision-making about parenthood is increased. Studies demonstrate that a significantly larger proportion of young men compared with young women overestimate female fecundity [4], and a larger proportion of men compared with women desire having a first child at an older age [4,17]. How can we increase the young men’s interest in initiating childbearing at an age where his female partner is still fecund? Furthermore, it is of importance that men begin to acknowledge their own infertility risk factors; for example, advanced age and obesity;

• • The postponement of childbearing has multiple roots, and one important factor appears to be the prolongation of the period young adults spent in education [1]. In many modern societies, the dual breadwinner pattern is frequent, indicating that both women and men want to pursue careers after achieving parenthood. The welfare state system, characterized by important features such as access to leave schemes for both parents, sufficient access to day childcare facilities, and legal equality between spouses, is in general considered to provide a proper framework for childbearing and child rearing [26]. It is of importance that we develop our societies in such a way that young couples would like to become parents, and find it possible to combine family life with working life during their most fertile years. Tough et al. demonstrated among childless couples how education, financial security, permanent employment and concerns about losing a job when on parental leave were important factors influencing decisions about timing of childbearing [17].

In conclusion, it is difficult to recommend to people when to have children. Many factors are involved, and the timing is an individual decision weighing these factors. However, it is important to increase individuals knowledge about the impact of age and other risk factors, in order for people to better make informed decisions about childbearing. It is equally important to develop society in such a way that both men and women can combine family and working life – if this is what they desire. This indicates that we need to work to develop societies where parents, for example, have sufficient access to high-quality day childcare and flexible leave systems for both fathers and mothers. Furthermore, we have to increase the possibilities of combining parenthood with long periods of further education; for example, by increasing the possibilities of financial support for student families, and helping to secure access to good accommodation possibilities for student families.

Financial & competing interests disclosure

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.