Changes in prenatal testosterone and sexual desire in expectant couples

Highlights

• Expectant mothers' T is negatively associated with their dyadic sexual desire

• Declines in expectant fathers' T is associated with decreases in their dyadic sexual desire

• Prenatal changes in T may facilitate evolutionary tradeoffs between parenting and mating

Abstract

During the transition to parenthood (TTP), both women and men report declines in sexual desire, which are thought to reflect an evolutionarily adaptive focus on parenting over mating. New parents also show changes in testosterone, a steroid hormone implicated in both parenting and mating, suggesting that changes in sexual desire may be associated with changes in testosterone. To test these associations, we followed a sample of heterosexual couples expecting their first child across the prenatal period. We examined prenatal changes in testosterone and two forms of sexual desire (solitary, dyadic). Expectant mothers showed prenatal increases in testosterone, and women's higher testosterone was associated with lower dyadic desire. Expectant fathers showed prenatal decreases in testosterone, and declines in men's testosterone were associated with lower dyadic desire. Testosterone was unrelated to men's or women's solitary desire. Our findings provide support for the idea that prenatal changes in testosterone contribute to an evolutionarily adaptive focus on parenting over mating during the TTP.

Introduction

Expectant parents experience many psychological and physiological changes during the transition to parenthood, including pre- to postpartum declines in sexual desire (Radoš et al., 2015). Perinatal changes in sexuality are thought to reflect an evolutionarily adaptive trade-off between parenting and mating: A diminished sex drive is adaptive insofar as it allows parents to prioritize parental investment, while temporarily putting future reproductive effort on hold (Gray, 2013). Physiologically, expectant parents also show changes in hormones, including testosterone, a steroid hormone associated with aggression and dominance (at higher levels) as well as caregiving and nurturance (at lower levels) (van Anders et al., 2011). Specifically, expectant mothers show large prenatal increases in testosterone, which return to pre-pregnancy levels postpartum (Edelstein et al., 2015; Fleming et al., 1997); expectant fathers show prenatal declines in testosterone, which rebound somewhat within the first postpartum year (Edelstein et al., 2015; Rosenbaum et al., 2018). Changes in testosterone are also thought to be adaptive in that they may facilitate infant protection, increase commitment to the relationship, and/or reduce mating effort in favor of caregiving and nurturant behaviors (Gettler et al., 2011).

Given the widespread belief that testosterone is related to sexual desire (Baumeister et al., 2001; Petersen and Hyde, 2011), and research implicating testosterone in parenting and mating (Barrett et al., 2013; Gettler et al., 2017; Gray et al., 2005), it has been assumed that declines in sexual desire during pregnancy may be due to prenatal changes in testosterone (Regan et al., 2003). In fact, there is some evidence to suggest that changes in testosterone may precede changes in sexual desire: Men who suffer from erectile dysfunction and women who report clinical levels of sexual dysfunction (e.g., due to hypoactive sexual disorder or menopause) show significant improvements in sexual desire after the administration of synthetically produced testosterone (Achilli et al., 2017; Bolour and Braunstein, 2005; Corona et al., 2016; Corona et al., 2014; Isidori et al., 2005). These findings suggest that increases in testosterone may promote sexual desire; however, it is important to note that such evidence comes primarily from studies of people with clinically low levels of sexual desire (or testosterone) and administration of synthetically-produced testosterone. Thus, it is difficult to extrapolate findings from these studies to the general population (Sader et al., 2005; van Anders, 2012; van Anders et al., 2005). Indeed, a growing body of research with healthy men and women provides contrary evidence, showing null or even negative associations between testosterone and sexual desire (Davis et al., 2005; Goldey and van Anders, 2011; Jones et al., 2018; McIntyre et al., 2006; van Anders, 2012). Moreover, to our knowledge, testosterone-sexual desire associations have rarely been tested among expectant women, let alone couples, making it impossible to assess whether such associations can help to explain changes observed in both men and women throughout the transition to parenthood.

Further, more recent research suggests that the relation between testosterone and sexual desire may depend on the type of sexual desire and participants' biological sex. Contemporary theories, based primarily on studies of college-aged and young adult participants, suggest that human sexuality includes both erotic and nurturant components (van Anders et al., 2011): Motivation for solitary erotic experiences, such as masturbation, which are arguably more erotic than nurturant, is thought to be facilitated by higher testosterone. Motivation for dyadic or paired sexual experiences, however, which tend to be more nurturant or intimacy-building, is thought to be facilitated by lower testosterone (van Anders, 2013). Nurturant experiences may be more socially accepted (and more easily achieved than erotic experiences) for women (Goldey et al., 2016); coupled with the fact that women's dyadic sexual desire may involve relational components that are not necessarily related to genital pleasure (van Anders, 2013), associations between testosterone and dyadic sexual desire may be stronger among women (especially heterosexual women) compared to men. For instance, in two cross-sectional assessments of 157 and 177 healthy college-aged men and women, van Anders and colleagues found that people with higher testosterone reported greater desire to engage in solitary sexual activities, but only women with lower testosterone reported greater desire to engage in paired sexual activities (Raisanen et al., 2018; van Anders, 2012). Further, men's testosterone was not related to their dyadic or solitary sexual desire.

Dyadic sexual desire may also be more sensitive to changes that occur during the transition to parenthood compared to solitary sexual desire: Expectant couples report declines in interest for most paired sexual activities (except hugging and kissing), but no changes in interest for solitary sexual activity (e.g., masturbation frequency; von Sydow et al., 2001). Thus, dyadic sexual desire may be more closely tied to changes in testosterone during pregnancy than solitary sexual desire. Moreover, given that pregnant women undergo large prenatal increases in testosterone, whereas expectant fathers undergo prenatal declines, associations between prenatal (dyadic) sexual desire and testosterone may also differ by sex.

Surprisingly, there is little published data on associations between testosterone and sexual desire during pregnancy; longitudinal work that tracks testosterone-sexual desire associations in expectant couples across pregnancy is also critically lacking. An early (and the only) review of studies that assessed either women's testosterone or sexual desire prenatally concluded that women's testosterone increased, while sexual desire decreased, during pregnancy (Regan et al., 2003); however, none of the studies reviewed measured both testosterone and sexual desire, and none assessed these constructs in men. A more recent cross-sectional assessment of 589 healthy pregnant women showed that expectant mothers' lower sexual function (including sexual desire) was not related to their prenatal testosterone (Erol et al., 2007). This study is limited by its cross-sectional design, and exclusive focus on women, which tells us little about how changes in prenatal testosterone might be associated with sexual desire in both couple members. Both the review and empirical study are further limited in that solitary and dyadic forms of sexual desire were not distinguished. An overall null association between testosterone and sexual desire may mask divergent associations between testosterone and solitary versus dyadic sexual desire.