Putative Mental, Physical, and Social Mechanisms of Hormonal Influences on Postpartum Sexuality

Abstract

Purpose of Review

Much research has documented changes in postpartum sexuality, including changes in sexual functioning and satisfaction for both the birthing parent and their partner(s). These changes are often linked to postpartum changes in hormonal and immune responses, which can have both direct and indirect effects on sexuality.

Recent Findings

Here, we review how postpartum sexuality may be changed via mental, physical, and social/relationship effects of a variety of hormones, including estrogens, progestogens, androgens, cortisol, and oxytocin. We also review the ways in which inflammation may act alongside hormones to influence postpartum sexuality.

Summary

We argue that, as each of these factors strongly influence the action of others, the next phase of research in postpartum sexuality must examine the bidirectional interactions of hormones and their effects on behavior, cognition, and social relationships.

Introduction

Pregnancy and parenthood bring about a cascade of changes in the endocrine and immune systems, which can directly impact sexual well-being. However, endocrine and immune systems also impact a variety of cognitive, behavioral, and social changes, which in turn may amplify or moderate the direct effect of hormones on sexual behavior. While the effects of each of these constructs on sexuality have largely been studied independently of one another, they do not work in a vacuum: interplay between systems is the rule rather than the exception.

Understanding both the direct and indirect effects of hormonal changes is particularly relevant for understanding changes in sexuality in pregnancy and the postpartum period—a time when parents experience drastic shifts in their body’s endocrine and immune function, as well as within their social context. We highlight the relevance of each hormones’ impacts on psychological, physical, and social health, in order to highlight a future research path that aims to understand the milieu of mechanisms driving sexuality changes in postpartum. In keeping with other recent reviews (e.g. [1],) we have attempted to refer to “postpartum parent” or “birthing parent” as appropriate, rather than explicitly gendered terms. Because much of the research has conflated sex and gender, we will use the term “female” when referring to research that claims sex differences. It should be noted that most research in this area has focused on cisgender women as birthing parents and mixed-sex couples as parents, and there is a critical dearth of research on sexuality- and gender-diverse parents and families.

Common Changes in Postpartum Sexuality

The first 6 weeks of the postpartum period is widely accepted as a time of significantly reduced sexual interest and activity for the parent who has given birth [2]. After these first 6 weeks, birthing parents have often physically healed enough to resume some partnered sexual activity; however, sexual functioning may continue to be impacted with lower sexual desire, arousal, and satisfaction commonly reported in the year postpartum [2–4]. One recent study found distinct trajectories for different groups of postpartum parents, with about half of birthing parents reporting few changes in their sexual function postpartum, one-third reporting moderate sexual dysfunction in the first 3 months postpartum but significant improvements by 1 year, and one-eighth reporting marked sexual problems that improved more slowly [3]. Changes in sexual desire is the most commonly reported issue postpartum, with most parents reporting at least some decrease in sexual desire within the first 3–6 months post-partum [5]. It should be noted, however, that some research points to short-term decreases in sexual desire as predictive of better—not worse—relationship and sexual satisfaction in new parents [6–8], suggesting the need for caution when conceptualizing such changes as sexually “dysfunctional.” For instance, decreased interest in sexual activities may serve as both a protective mechanism for the infant (i.e., more attention from the parents) and for the birthing parent as their body recovers [6].

In terms of arousal and orgasm, delivery mode (e.g., vaginal vs. caesarian) has been often proposed as a possible source of postpartum sexual arousal and orgasm difficulties. While there is no strong evidence that birthing mode change vaginal arousal for the long term [9–12], people who have undergone episiotomy and/or experienced perineal tearing during childbirth generally report greater sexual pain than those who did not [4]. To that end, increased pain during vaginal penetration is also common among birthing parents but tends to resolve within 12 months unless accompanied by other changes in the relationship [6, 12]. In sum, most couples resume to their prepartum sexual functioning within a year, with a small but significant minority of birthing parents experiencing either psychological or physical sexual difficulties that persist beyond this transitional time [2].

Changes in Hormones Across Pregnancy and Postpartum

Changes in endocrine function impact sexual function, albeit in a complex and non-linear fashion [13, 14]. Key hormonal changes during pregnancy include dramatic shifts in estrogens and progestogens, as well as (relatively) more moderate changes in androgens and cortisol. Estrogens (particularly estradiol and estriol) and progestogens steadily increase throughout gestation—peaking in the third trimester—and dramatically decrease in the immediate postpartum period. Similarly, androgens (e.g., testosterone) and glucocorticoids (e.g., cortisol) increase through gestation and decline gradually during the postpartum period [15–18]. Unlike other steroid hormones, DHEA tends to decreases during the third trimester and continues to decrease throughout the postpartum period [19]. During the postpartum period, stress can influence cortisol production, which is discussed further below. Given antagonistic interactions between the hypothalamic pituitary adrenal (HPA) and hypothalamic pituitary gonadal (HPG) axes, some of these fluctuations—in particular, estrogens, progestogens, and cortisol—may occur in tandem. Each of these changes may independently influence psychosocial and behavioral changes, and together their action may amplify each other’s effects.

Estrogens

Because estrogens have been associated with a myriad of psychological and physical effects, they have been proposed as a major contributor to sex differences across a range of health conditions [20].

Effects on Mental/Psychological Factors

Greater elevations of endogenous estrogen during pregnancy (and thus a larger sudden estrogen withdrawal in postpartum) has been linked to more severe depressive symptoms (i.e., onset of postpartum depression [PPD]) and increased pro-inflammatory cytokines in the postpartum period [21]. A pathway linking postpartum inflammation and depressive symptoms may be through estrogen’s influence on neurotoxic kynurenine metabolites [22–24], which may disrupt the delicate processes of neural reorganization and neurogenesis during the first 6 months postpartum [25–27]. In other words, by interrupting key aspects of neuroplasticity that help the brain to adapt to parenthood, excessively sudden estrogen withdrawal may contribute to postpartum mental health disturbances—which in turn contribute to sexual dysfunction.

Estrogens and the serotonergic system have also been found to have a bidirectional relationship that act synergistically to achieve homeostasis [28]. However, dramatic decreases in estrogen (such as during the postpartum period) may interrupt the estrogen-serotonin balance and may produce longer-lasting depressive symptoms. Further, as estrogens can have an anti-inflammatory role, the dramatic decreases in estrogen production after childbirth may work in tandem with inflammatory responses that suppress sexual desire while the birthing parent recovers (see below).

Effects on Physical Health

For premenopausal people with vaginas, estrogen also plays an important role in sexual function such that estrogen supports sensitivity and plasticity of vulvar epithelium as well as vaginal lubrication, and thus vaginal functioning as a whole [13, 29, 30]. When estrogens are withdrawn, vaginal function is negatively impacted [13, 30]. Breast-/chest-feeding is associated with lower systemic estrogens, further contributing to vaginal dryness [9, 31]. When there is an increased need for tissue repair after birth, this decrease in vaginal-repairing estrogens likely contributes to sexual pain. While pain may resolve itself over time, how couples handle the pain can influence both the persistence of the pain and the couple’s sexual dynamics. [32] For instance, both hostility and solicitousness around sex and sexual pain from partners are often associated with more pain and poorer sexual outcomes [32].

Effects on Social and Relationship Factors

Estriol, the most common form of estrogen during pregnancy, is associated with greater responsiveness to social support [33]; to the extent that social support improves relationship/sexual satisfaction, the higher expression of estriol specifically may predict postpartum sexual function. Relatedly, increased estradiol is associated with lower levels of attachment avoidance and high levels of intimacy motivation [34]. Perhaps pregnancy-related increases in estrogens promote intimacy efforts between partners during gestation, which may work as a protective agent for dyadic adjustment in the postpartum period. If so, this would buffer against the negative effects of lower sexual function postpartum on the couples’ relationship satisfaction.

Interestingly, estrogens appear to amplify individual differences in social reward sensitivity [35]: that is, among people who are predisposed to be interested in social interactions, estrogens increase this interest. Thus, it is possible that, while most birthing parents experience a decline in estrogen production from pregnancy to postpartum, this amplification of underlying individual differences contributes to the diverse range of changes in sexual desire in post-partum—with some parents reporting moderate changes that resolve quickly and others reporting very marked and lasting declines.

Progesterone

Progesterone—literally, a “pro-gestation” hormone—prepares the body for pregnancy by promoting implantation, preventing contractions of the uterus during early pregnancy, and regulating maternal immune function [36]. In fact, much research suggests that parturition (childbirth) is stimulated by rapid withdrawal of the anti-inflammatory effects of progesterone, which in turn leads leading to an acute inflammatory response that triggers uterine contraction. [37]

Effects on Mental/Psychological Factors

In postpartum, rapid withdrawal of progesterone is associated with increased inflammation, which in turn may amplify psychological responses to stress [38, 39] and suppress sexual desire as described below. Moreover, higher progesterone coincides with within-person decreases in sexual desire [40], potentially reflecting a shift in reproductive investment towards the new offspring. Several studies investigating neuroplasticity during pregnancy have suggested that increased progesterone (alongside increased estrogens) may be responsible for changes in how emotional information is processed, increasing attention to offspring-related cues and decreasing interest in sexual stimuli [41–43]. Thus, one might assume rapid decreases in progesterone during the postpartum period would increase sexual desire; however, decreases in progesterone have been associated with increases in factors that seem to promote depressive symptoms (e.g., IL-1B and neurotoxic kynurenine metabolites) [21, 44, 45]. Thus, progesterone during the postpartum period may indirectly impact mental health and sexual function. Recently, progesterone loading has been proposed as a treatment for people experiencing PPD [46].

Effects on Physical Health

Progesterone has also been implicated in wound healing, specifically among cervical injuries [47, 48] (for opposing results, see [49]). Increased progesterone in the third trimester promotes cervical integrity and accelerated cervical healing [48], potentially protecting against risk of dyspareunia. Relevant to sexual pain, much research suggests that higher progesterone is associated with decreased pain sensitivity [50] with progesterone serving an analgesic role in reducing the negative emotional experience associated with pain [51]. Thus, it is possible that the drop in progesterone from pregnancy to postpartum may contribute to postpartum sexual pain. However, other work suggests that there is a decoupling of hormonal influences on pain during pregnancy and postpartum [52].

For individuals who breast-/chest-feed during the postpartum period, progesterone and estrogens are suppressed [53, 54]. Sex steroid suppression during the lactation period is thought to act as a natural form of contraception promoting longer birthing intervals, which allows for both physical repair and energy allocation to the new baby[55].

Effects on Social and Relationship Factors

Increased progesterone seems to influence both brain plasticity, particularly in the limbic system—known for its role in intense emotional response [41]. Furthermore, increased progesterone levels seem to correspond with increased relationship commitment [56], though assessment of exact measurement of progesterone levels, and this phenomenon is needed. Progesterone has been cited in physiological attunement among women friends [57], suggesting that changes in progesterone may influence psychological synchrony in couples. If so, we would expect that birthing parents who have larger or more sudden changes in progesterone postpartum may experience greater desynchrony with their co-parents—which in turn could lead to relationship dissatisfaction.

DHEA

DHEA is a prevalent precursor hormone that aids in the production of sex steroids like estrogens and testosterone [58]. DHEA and cortisol interactions have also been found to help regulate inflammatory responses [59]. Though DHEA seems to be an indirect but important influence on many factors within the body, investigations on postpartum DHEA are limited.

Effects on Mental/Psychological Factors

DHEA and cortisol interactions have been linked to mental health conditions (e.g., severe anxiety and depression) both during pregnancy [60] and during the postpartum period as well as several years after birth [61]. In general, higher levels of DHEA is linked to greater psychological stress [62], and higher DHEA may amplify the desire-suppressing effects of stress [63–65]. However, as DHEA can serve as a precursor to other hormones (e.g., estrogens), supplementation of very low DHEA levels can improve psychological and sexual function [66]; thus, moderate levels of DHEA may buffer against postpartum mental health effects of other hormonal changes. In females, better cognitive functioning has also been linked with higher DHEA levels [66], which may influence cognitive processes during the postpartum period, such as attention allocation to sexual cues.

Effects on Physical Health

As DHEA impacts the production of sex steroids, decreases in DHEA may result in indirect negative effects on sexual function [66]. There is evidence that DHEA influences the inflammatory system [59], which in turn may influence sexual functioning (see below). Finally, DHEA supports vulvovaginal tissue health and a healthy, Lactobacilli-dominant vaginal microbial environment [67], both of which undergo significant changes during childbirth [68]. Likely, postpartum changes in DHEA production may influence the rate at which the vaginal microbiome re-integrates following birth, which in turn may influence vaginal arousal and pain during sex [69].

Effects on Social and Relationship Factors

There is some evidence that DHEA is increased among cisgender women who were separated from their partner or single compared to cisgender women who were in long-term relationships [70]. Additionally, affectionate communication has been linked to healthier stress hormone levels, in particular the cortisol:DHEA ratio [71]. While there are not clear direct effects of DHEA, healthier relationship dynamics appear to be related to more regulated HPA axis function. Both healthier relationship dynamic and HPA function likely relate to better sexual function.

Cortisol

Cortisol is most commonly known for its role in the stress response. However, cortisol plays an important part in metabolism and immune response and interacts with estrogens and progestins to create a uterine environment in which a fetus can be sustained [72]. As the main product of the hypothalamic–pituitary–adrenal stress axis, cortisol has a mutually antagonistic relationship with ovarian hormones: as one increases, the other is typically suppressed [73]. Thus, cortisol’s effects on postpartum sexuality may be indirect, through inhibition of the production of estrogens and progesterone. That said, pregnancy is a unique context in that cortisol has been shown to rise throughout pregnancy even as ovarian hormones also rise [74, 75]. In fact, it has been suggested that pregnancy is one of the few times in which relatively higher levels of cortisol are tolerated by the body, as higher cortisol contributes to increased energy availability needed in a healthy pregnancy [76].

Effects on Mental/Psychological Factors

Stress, happiness, and depression have been linked to cortisol during the postpartum period [77]. For instance, pregnant people who experience severe anxiety show heightened cortisol levels [60]. While more severe depression symptoms have been linked to increased cortisol [78, 79], there have been mixed results on cortisol’s influence on PPD [80–84]. During pregnancy, lower cortisol levels seem to help conserve conflict monitoring and resolution capacities [85]. Though not thoroughly assessed in birthing parents in the postpartum period, increased cortisol can have effects on cognitive responses to sexual stimuli [86], as well as longer term effects suppressing sexual desire [87]. There has been some work suggesting that multipara (people who have given birth multiple times) may have lower cortisol during pregnancy than primipara (those giving birth for the first time) [88], with greater links between cortisol and negative mood in primipara. This suggests in turn that cortisol may have a greater influence on sexual function among first-time parents.

Effects on Physical Health

Though spikes of cortisol in response to stressors are helpful for survival, chronic exposure to increased cortisol has been linked to many physical health outcomes. Flatter diurnal cortisol rhythms throughout the daytime are related to poorer mental and physical health outcomes, including poorer immune and inflammatory function [89]. Indeed, cortisol has been shown to be a significant predictor of postpartum physical health problems, particularly among ethnic and racialized minority groups [90]. In particular, higher cortisol levels are related to higher risk of cardiovascular disease [91, 92]. The vascular system is crucial for vaginal blood flow (i.e., arousal); thus, increased cortisol can have a variety of effects on physiological sexual arousal (e.g., decreasing vaginal arousal) [65, 86, 93]. Indeed, there is some evidence that hypertension during pregnancy is associated with increased rate of cortisol production and metabolism [76]. As hypertension is associated with significantly poorer sexual function, particularly in arousal domains [94], it is possible that cortisol-related increases in blood pressure during pregnancy may contribute to postpartum sexual arousal.

Effects on Social and Relationship Factors

Cortisol seems to play a bidirectional role in conflict behaviors among people in close relationships. For instance, couples with more attuned cortisol levels tend to have fewer conflict behaviors [95]. Further, the amount of affectionate communication from a partner predicts both waking and evening cortisol levels, such that more affectionate communication promotes healthier cortisol function [71]. Additionally, family support has been found to serve as a protective factor against increased stress and cortisol levels among low-income Mexican–American folks during postpartum [96]. Finally, there is some research suggesting that among cisgender women with sexual trauma histories, dysregulated cortisol responses contribute to problems feeling emotional closeness or intimacy with male partners [97], suggesting that cortisol may play a role in sexual relationship dissatisfaction. That said, this research has not been extended to postpartum or parenting contexts.

Testosterone

There is relatively more research on the effects of testosterone on sexuality among postpartum parents and their co-parents. Testosterone fluctuations are some of the only hormonal fluctuations to happen noticeably in tandem between partners [98]. Testosterone fluctuations have been examined in both the birthing parent and the non-birthing parent [99, 100].

Effects on Mental/Psychological Factors

Higher postpartum testosterone levels are associated with greater risk for postpartum mood disorders for the birthing parent [101, 102]. However, some work suggests that testosterone’s main contribution to postpartum mental health is to amplify pre-pregnancy mental health issues and risk factors [103], specifically in cisgender women with a history of sexual trauma [104, 105]. While some evidence suggests that very low testosterone can contribute to fatigue [106, 107], a notably important factor predicting sexual function in new parents [3], recent randomized controlled trials have failed to find positive effects of testosterone on fatigue or sexual function in (non-pregnant) cisgender women [108].

Effects on Physical Health

Testosterone does not appear to have a consistently observed direct effect on physical health in the postpartum period [99]. However, there are not many studies that examine direct physical health impacts of testosterone on the birthing parent. Much of the research on testosterone and physical health—as it relates to pregnancy and postpartum—focuses on the effects on the offspring. Testosterone may, however, have indirect, positive effects for physical health in the post-partum. There are a growing number of studies suggesting synergistic effects of testosterone with estrogens in promoting vulvovaginal integrity, increasing the speed of healing micro-abrasions in the epithelium, and improving vaginal microbiome health (see [109] and [110] for review), all of which are critical for postpartum vaginal health.

Effects on Social and Relationship Factors

Lower testosterone for both parents in a heterosexual couple is associated with greater nurturance of the newborn and better caregiving [100]. Further, maternal and paternal testosterone synchrony in heterosexual couples predicts postpartum relationship investment [98]. Decreased testosterone in expectant, cisgender fathers [111, 112] is associated with lower dyadic desire[113], but also greater support for mothers, leading to higher relationship satisfaction [114]. Increased testosterone in expectant, cisgender mothers is associated with lower dyadic desire [113]. Decreased sexual desire in the peri- and postpartum period may promote a greater focus on parenting the newborn and provide a reprieve for the birthing parent’s body after delivery and thus may be adaptive [6, 113]. While decreases in testosterone likely have similar outcomes in lesbian couples, the research to date on lesbian couples’ hormone fluctuation during pregnancy and the postpartum period has not established significant testosterone changes in the non-birthing parent of lesbian couples [99].

Oxytocin

Oxytocin increases gradually throughout pregnancy and peaks during the first and second stages of labor [115]. Oxytocin is also heightened in lactating parents, with higher levels in multipara vs. primipara [115].

Effects on Mental/Psychological Factors

Oxytocin has become very popularly known as the “love hormone.” While oxytocin does play a role in bonding, particularly between parents and their infants [116], it also seems to play a role in mental health. Differences in plasma oxytocin have been found in individuals with and without PPD, such that cisgender women with PPD experience an oxytocin drop in the immediate postpartum period [117]. Though there are mixed results on endogenous oxytocin levels and postpartum mood [117, 118], there is evidence that suggests peripartum exposure to exogenous oxytocin (e.g., during induced birth) may have limited longer term effects on mood [119]. That said, endogenous oxytocin predicts lower anxiety and better responses to stress postpartum, particularly among primipara [120]; as stress is a particularly important risk factor for postpartum sexual dysfunction [3], it is possible that oxytocin may be a protective factor via effects on mental health.

Effects on Physical Health

Oxytocin is also known for its role in birthing parents’ bodies during labor and postpartum. During labor, oxytocin stimulates uterine contractions at the start of labor and promotes further contractions to progress the labor [115]. In recent laboring practices, exogenous oxytocin has been used to induce labor [121]. However, there is some recent research to indicate that prenatal exposure to exogenous oxytocin may influence oxytocin production in the postpartum [119]. Further, oxytocin is in involved in the positive feedback loop that is breast-/chest-feeding. Oxytocin promotes milk to drop into the areola for quick access, suckling promotes oxytocin release, and the flow of oxytocin promotes further milk production [122]. There is some evidence that oxytocin may also contribute to vaginal health and improve vaginal lubrication [123], although these findings have been limited to postmenopausal patients and need to be extended to postpartum contexts. Finally, relevant to the discussion of inflammation below, oxytocin has an important anti-inflammatory role [124], buffering against the pro-inflammatory effects of elevated cortisol during pregnancy and postpartum [125, 126].

Effects on Social and Relationship Factors

While heightened oxytocin in postpartum may increase interest in one’s pair bond (i.e., increase relationship satisfaction) [127], it may also decrease sexual interest in new parents [128]. As oxytocin plays an important role in both bonding and mood, it is likely that oxytocin fluctuations play an indirect role in the sexual function and/or behaviors of people in the postpartum period. For example, some research in non-pregnant heterosexual couples suggests that sexual function is improved in male partners of cisgender women using oxytocin treatments for low sexual desire [129], suggesting that oxytocin’s effect on sexual functioning may act on a couple’s attunement to each other. Further research is needed to fully understand the potential mechanisms by which oxytocin influences sexual desire or motivation in the postpartum period.

Inflammation and Inflammatory Cytokines

The endocrine and immune systems work together to maintain health and reproductive homeostasis [130]. Each system signals to the other, with the endocrine system using hormones and the immune system using cytokines, chemokines, and other small signaling molecules. These signals can trigger up- or down-regulation both within and across systems. This “immocrine” communication is particularly important to educate the parent’s body to accept the fetus as a semi-allogeneic graft (i.e., not a foreign object) and prevent rejection during early pregnancy. Of note, inflammatory cytokines have been shown to have hormone-like properties, including the ability to modulate neural function through action on dedicated receptors [131], and both local and systemic effects (mimicking autocrine, paracrine, and endocrine functions). Fluctuations in both the immune and endocrine systems are separately and interactively linked with psychological, cognitive, behavioral, and (likely) sexual fluctuations. As such, we include inflammatory signals in our review of hormonal changes during postpartum.

Effects on Mental/Psychological Factors

After birth, the body requires at least several weeks of recovery. Both physical recovery and physiologic adjustment back to pre-pregnancy homeostasis involve massive changes in the birthing parent’s inflammatory profiles. Dramatic upswings in birthing parents’ inflammatory profiles after birth (relative to immune suppression during pregnancy) may result in the milieu of symptoms known as “sickness behaviors” [132]. These behaviors are thought to be adaptive as they help down-regulate unnecessary physical strain while the immune system is busy fighting infection and healing wounds [132]. Common sickness behaviors include fever, lethargy, and anhedonia [133]. In the context of pregnancy and postpartum, decreases in sexual interest stemming from changes in inflammatory signaling may be a manifestation of sickness behaviors and are likely adaptive during the immediate postpartum period as the body heals from birthing trauma [6]. Relatedly, increased inflammation can contribute to depression via action on cytokine circuits that suppress reward sensitivity and motivation [134, 135], which likely plays a role in PPD and related decreased sexual desire.

The significant increase in estrogens produced during pregnancy leads to decreases in pro-inflammatory responses (such as cytokines interleukin-6 (IL-6) and tumor necrosis factor (TNF) and increased anti-inflammatory responses (such as cytokines interleukin-4 (IL-4) and interleukin-10 (IL-10) [136, 137]. Further, progesterone has been found to suppress the production of Th1 cytokines (multifunctional sources of inflammatory cytokines), enhance Th2 cell activity, and modulate the shift from Th1 to Th2 cytokines [138]. This immune shift can serve not only as a protective factor for the fetus but can reduce the severity of some inflammation-related diseases for the pregnant parent [136, 139]. However, down-regulation of inflammatory response can leave the pregnant parent at risk for contracting more severe infectious diseases (e.g., influenza)[136]. If the immune system becomes activated during pregnancy—known as maternal¹ immune activation—the fetus may be introduced to a cascade of cytokines and other inflammatory signals, which has been found to impact fetal neural development later in life [140, 141]. Though much of the research focus has been on fetal outcomes, immune activation during pregnancy likely also has a longer term impact to the pregnant parent. Parental outcomes from maternal immune activation pose interesting questions in regard to mating and parenting behaviors from an evolutionary standpoint. Speculatively, immune activation during pregnancy may lower parental investment in the current offspring and redirect interest in new offspring, potentially altering the trajectory in which sexual desire returns postpartum; this hypothesis warrants further investigation.

Effects on Physical Health

Increased inflammation can have negative effects on many aspects of physical health. For instance, increased inflammation can increase pain sensitivity, which could increase sexual pain for some individuals [142, 143]—however, as noted above, there are some countervailing effects of progesterone regulating pain sensitivity in pregnancy. That said, some changes in autoimmune conditions—like the changes that pregnancy and postpartum bring upon—may improve sexual functioning. For instance, during pregnancy and post-partum, individuals with rheumatoid arthritis tend to report better sexual function [144].

Effects on Social/Relationship Factors

Females may be more sensitive than males to the effects of social stress and isolation. For example, females have greater increases in inflammation when in a state of isolation and/or when social support is low [145, 146]. Relatedly, an increased inflammatory state seems to increase sensitivity to social reward [147, 148]. These effects may be particularly enhanced for birthing parents in the postpartum period when both socialization and inflammation are fundamentally altered, which may further the negative impact of inflammation on sexuality.

Conclusions and Future Directions

Although there is a growing body of research documenting the trajectory of sexual function and behavior during the postpartum period, there is much less of an understanding of the psychophysiological processes behind postpartum shifts in sexuality. While this review is focused on postpartum sexuality, the research presented is largely in non-pregnant, non-postpartum samples. Based on previous work, we can make tentative inferences about hormonal and immune influences during pregnancy and postpartum on sexuality; however, investigations directly pertaining to pregnancy and postpartum immocrine mechanisms is lacking overall.

This review has attempted to highlight many potential mechanistic avenues for future research; specifically, the need for a more holistic approach to these research questions. As these systems often work in tandem, promising lines of investigation lie within the immune-endocrine interactions, hormonal interactions, and bidirectional behavioral-environmental-immocrine interactions. Much of the previous research has examined these systems independently, which may overlook important contextual pieces about how these systems influence one another and behavior. Similarly, while much research has investigated linear relationships in hormonal effects, there is increasing evidence for contrasting behavioral effects at low vs high levels, particularly in the context of hormone interactions (e.g., [149]). For example, the effects of estrogens on inflammation differ at low vs high levels of progesterone, with subsequently different effects on women’s sexual desire [150].

Given this, modeling dynamic interactions between estrogens, pro- and anti-inflammatory cytokines, and sexual behavior may be a particularly fruitful area for future research on postpartum sexuality, as both estrogens and cytokines ebb and flow with changes in sexual activity [151, 152]. This estrogen-cytokine interaction may be of particular interest in the postpartum period as there is a dramatic shift in both systems that may influence sexual behavior. Another potentially fruitful avenue of investigation during the postpartum period would be the cortisol-testosterone ratio. The coordination of cortisol and testosterone has been found to influence social orientation (e.g., shifting the balance between socially dominant and nurturant behaviors), which may be of interest in the hormonally and behaviorally tumultuous postpartum period [153, 154].

A broader focus on the variety of mechanisms by which postpartum hormonal systems influence sexuality may further inform research that includes both partnered and solitary sexuality. As a return to partnered sex has been seen as relatively important to couples (and thus to researchers), many studies construct the narrative of postpartum sexuality in the context of partnered sexual behavior and how sexuality changes may impact relationship function and satisfaction during this time. This focus neglects other important aspects of human sexuality such as solitary sex, masturbation, and fantasy. Notably, in this review, we made an effort to find hormonal studies that differentiated postpartum participant’s dyadic and solo sexual desire; however, there seems to be dearth of research into hormonal influences on these distinct facets of desire. In addition to the benefits that solitary sexuality has for the birthing parent’s own mental and sexual well-being, neglecting solitary sexual behavior overlooks potential changes in the sexual interest system, which in turn may direct partnered sexual behavior.

Finally, there is an expanding base of research suggesting that sexual and gender minority people may differ in some key hormones—most notably in cortisol and DHEA, corresponding to their higher exposure to discrimination stress [155]. And, some trans* folks use hormonal treatments as part of their gender-affirming care; however, little is known about the long-term mental and physical health effects of altering or stopping this care during pregnancy or postpartum [156]. Despite this evidence of key differences from heterosexual/cisgender populations on which much hormonal research is based, there is shockingly little known about hormonal fluctuations experienced by LGBTQ + individuals and couples during pregnancy and postpartum. We join others—including the NIH [157]—in calling for more research in these populations, with particular interest in hormonal fluctuation and synchrony between lesbian couples during the postpartum period, postpartum changes in trans-individuals with a history of using hormone replacement therapies, and how physiological stress response and allostatic load influences postpartum immunocrine transitions in gender and sexual minority people.