Demography – Hormonal Contraception Reduces Not Only the Birth Rate But Also the Desire to Give Birth

People in developed countries have had only one or two children in recent years, and  this applies, surprisingly, to all developed countries regardless of their previous history, whether they are traditionally Catholic countries such as Spain, Italy, Ireland and Poland, traditionally liberal and democratic states such as Britain, the USA, France and Sweden, Islamic countries such as Qatar, Kuwait,  Bahrain  and Turkey, Buddhist states such as Thailand, Japan and Singapore, a Confucian state such as Taiwan,

communist states such as China and Cuba, or former communist states such as Russia, Ukraine, the Czech Republic and Hungary.

In the pre-industrial era, people had an average of 5-8 children, and this number decreased as societies developed (here). In developed countries, birth rates dropped significantly during the 20th century, probably due in large part to women's expanded rights. Worldwide, birth rates have been falling since the 1970s (here, here), most likely due to greater access to contraception. To maintain a stable population, each mother should give birth to at least 2.2 children (not every woman gives birth, here), which corresponds to a birth rate of about 12-15 live births per 1,000 people per year. In Europe, women have between 1.1 (Spain) and 1.8 children (Bulgaria, here). Almost no developed country is reproducing at replacement level anymore; however, the population explosion continues in developing countries (see the table of countries here).

Some reasons for the declining birth rate are obvious: affordable and safe contraception enables family planning, and a smaller family improves the economic situation of poorer households and gives wealthier ones more leisure time. In addition, later marriages increase the age of first-time mothers, and fertility drops sharply with the age (here). Male fertility is also reportedly falling (here). The reasons for such a sharp decline in the number of children per family below two are not entirely clear. Supposed reasons include, for example, a hedonistic emphasis on a comfortable life, feminist views on the importance of a career for women's happiness, and progressivist attacks on the family. Political arguments from the left mention allegedly growing inequality and an epidemic of despair in Western society (here, do the African massacres make people more equal and happier?).

Economic uncertainty, expensive housing, the cost of raising children, high inflation, fear of the climate situation, and war (here) are also mentioned. In addition, the effects of vaccination are now considered when explaining the further fertility decline during the last few years (here). Despite all the reasons given, I find the uniform decline in the number of babies in families from California to Japan difficult to understand. Social changes and generally accessible contraception are the main reasons why we do not see families with 6 to 12 children in Europe, but they hardly explain why so many people have only one child or none. I can think of a completely trivial reason: the natural women’s desire for a child may have diminished. Traditionally, little girls play mothers with their dolls, and eagerly cuddle real babies as they grow up; the desire for a child from the beginning of adulthood has always been one of the strongest psychological traits of a woman.

The affection for a cute toddler outweighed the appeal of vacations or digital entertainment. The biological desire for a real child is unlikely to be weakened by inflation or environmental concerns. Bur what if modern contraception itself diminishes that desire? For example, the combined oral contraceptive pill, containing progestin and estrogen, completely changes the levels of hormones in the blood during the monthly cycle, as shown in the following figure (Trends in Ecology and Evolution, here); the yellow, green, red and blue lines show the concentrations of the hormones FSH, LH, progesterone/progestin, and estrogen, respectively, with (a) showing a normal cycle and (b) a cycle using the pill.

 

The figure shows that the pill reduces estrogen levels throughout the cycle (blue line). High estrogen levels during a normal cycle have a positive effect on mood, which is best during ovulation, making women feel more attractive (here) and more desirable to men (here). Libido increases during ovulation and a woman is more inclined to have an intimate relationship (here). Higher estrogen levels during the cycle improve attention and reduce ADHD symptoms (here). In addition, estrogen is known to increase the amount of oxytocin – called the love hormone – in the blood, as well as the number of oxytocin receptors in the brain. Oxytocin is a hormone important for forming social relationships, emotional bonds and maternal behavior (a typical experiment shows that a sheep starts caring for a stranger’s lamb after being injected with oxytocin, here).

Modern contraception is used worldwide (here). Most contraception forms have some effects on physiology or psychology. Hormonal contraception is suspected of having an effect on brain structures (here), but this has not been studied much, perhaps due to resistance from pharmaceutical companies. What is certain is that hormonal contraception reduces estrogen levels, which could affect behavior related to establishing contacts and the desire to get pregnant. As only a fraction of women use the pill, the considered effect may explain only a part of the observed decline in birth rates. However, given the wide debate about the reasons for this decline and its importance, it is striking that possible effects of the pill on the desire for a baby have not yet been considered.