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Original Research: Lead Article

Effect of Parity on Sexual Function

An Identical Twin Study

Botros, Sylvia M. MD; Abramov, Yoram MD; Miller, Jay-James R. MD; Sand, Peter K. MD; Gandhi, Sanjay MD; Nickolov, Angel MS; Goldberg, Roger P. MD

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doi: 10.1097/01.AOG.0000207677.03235.76
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Female sexual function is an important quality-of-life issue and is influenced by a variety of psychological, relational, and physical factors.1 Childbirth represents a central event in a woman's reproductive lifetime, in physical and psychosocial terms, with the potential to impact female sexual function across all of its domains. Although up to 25% of women report diminished sexual function that persists at 6 months postpartum,2,3 no prior studies have focused on the potential long-term sexual repercussions of childbirth.

Sexual function represents a key aspect of female pelvic health, which has only very recently emerged as an openly discussed subject. Barrett et al3 demonstrated that only 15% of women with a sexual problem postnatally reported discussing it with a health care professional. Many women, and indeed many physicians—possibly due to paucity of information4—have been reluctant or too embarrassed to confront these inherently private physical and functional changes.

The purpose of this study was to evaluate the long-term effects of childbirth and mode of delivery on sexual function by using an identical twin study design. This design provides a “biologic” control group that eliminates genetic variance, and thus provides unique insight into the impact of environmental risk factors. Our aim was to compare the sexual function scores of twins who had children with those of their counterparts who did not, and to compare the scores of parous twins who delivered by different modalities.


An extensive survey including demographic, historical, and obstetric information as well as validated questionnaires was administered to 342 twin sister pairs (n = 682) of whom 271 pairs (n = 542) were monozygotic. The questionnaires included in the survey were the short form of the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire (PISQ-12), the short form of the Incontinence Impact Questionnaire, and the Pelvic Floor Distress Inventory. Data were obtained at the 2003 and 2004 Twins Day Festival, the world's largest annual gathering of twins in Twinsburg, Ohio.

In 2004, subjects were asked if they had filled out the survey in the prior year and were refused participation if they had. Each participant anonymously completed the survey without assistance by the physicians and research assistants administering the study. Sociodemographic, environmental, surgical, and obstetric factors were analyzed for possible impact on total PISQ-12 scores and individual items.

The PISQ was previously developed and validated to evaluate the effects of urogynecologic symptoms on sexual function in patients with urinary incontinence or pelvic organ prolapse. The 12-item short form was validated in 2003.5 Each question receives a score from 0 to 4, with higher scores indicating better sexual function. The 31-item questionnaire can be subcategorized into 3 domains: emotional, physical, and partner related.6 For this study, using the short form, subcategories were analyzed by individual questions in the PISQ-12 as recommended by Rogers et al.5

Introductory questions to the PISQ-12 were administered to obtain information about current sexual activity or reasons for absence of sexual activity. Only subjects who were currently or recently (within 6 months) sexually active were instructed to complete the PISQ-12. A logistic regression analysis was performed to identify predictors of sexual activity in the sample of 271 monozygotic twin sister pairs. A subset of this population, 138 identical twin pairs (n = 276), was identified in which both sisters were sexually active and were included in the majority of analyses. Only the findings related to sexual function are presented in this article. Findings regarding urinary incontinence and anal incontinence have been previously reported.7,8

A further subset of 29 twin pairs discordant for parity was identified in the data set and comparison of mean PISQ-12 scores were performed using the paired 2-tailed t test.

To evaluate multiple covariates, a regression model with all sexually active monozygotic twin pairs was created. After univariable analysis, stepwise multivariable linear regression models for repeated measures were used to account for correlated data within twin pairs.9 Three models were used: 1) 138 sexually active identical twin pairs (n = 276), to evaluate the effect of parity and general risk factors; 2) 98 sexually active parous-parous twin pairs (n = 196), to examine the impact of birth mode; and 3) 76 sexually active twin pairs with previous vaginal deliveries only (n = 152), to examine the role of episiotomy and operative delivery.

Further linear regression analyses were performed using the answers to individual questions from the PISQ-12 as outcomes to evaluate emotional, physical, and relational parameters. A P value of .05 or less was considered statistically significant. Data were analyzed with SAS version 8.2 (SAS Institute, Inc., Cary, NC). Institutional review board approval was obtained from the Evanston Northwestern Healthcare Research Institute before implementation of the study.


Of the 271 monozygotic twin pairs (n = 542), 352 (65%) twins were sexually active and 190 (35%) were not sexually active. Women who were sexually active were more likely to be premenopausal and multiparous (Table 1). Reported reasons for no sexual activity were lack of a partner (68%), lack of desire (11%), partner's impotence (7%), partner's lack of desire (2%), and multiple or other reasons (12%). Less than 0.5% of women cited pain or irritation as a reason for not having sexual relations.

Table 1
Table 1:
Comparison of Demographic Factors Between Sexually Active and Nonactive Women (542 Monozygotic Twins) by Multiple Logistic Regression Analysis

Twenty-nine twin pairs discordant for parity were identified in the data set. The parous and nonparous twins were similar in terms of age, body mass index (BMI), prior surgery, and stress incontinence. They were not similar in terms of urge incontinence; 32% of parous twins had urge urinary incontinence compared with 7% of nonparous twins (P = .008). Mean PISQ-12 scores were compared between groups and parous twins scored significantly lower than nonparous twins (93.5 ± 11.5 versus 102.5 ± 15.5, P < .001).

Among the 138 sexually active twin pairs, 99.6% fully completed all portions of the sexual questionnaire. Demographic and obstetric characteristics of the study sample (138 twin pairs), including modes of delivery, are presented in Table 2. Among sexually active women, 13.4% stated that they seldom or never felt sexual desire, 16.7% seldom or never climaxed, 6.4% seldom or never felt excitement with intercourse, 7% usually or always had pain, and 2% usually or always had leakage during intercourse (Table 3).

Table 2
Table 2:
Demographic Information Regarding 138 Pairs of Sexually Active Twins (n = 276)
Table 3
Table 3:
Frequencies of Individual Items in the Questionnaire

The mean (standard deviation) PISQ-12 score was 99.3 (11.7). Age of 50 years or older (difference in mean PISQ score −5.4, P = .019), stress urinary incontinence (–3.3, P = .02), urge urinary incontinence (−5.9, P < .001), parity (−6.5, P < .001), and fecal incontinence (−5.7, P = .048) were associated with decreased mean PISQ scores in the univariable analysis. In the multivariable regression analysis, parity (P < .001) and urge urinary incontinence (P = .009) were the only factors remaining independently predictive of diminished sexual function. Significantly higher mean scores were observed for nulliparous women compared with primiparous women (105.5 versus 99.5, −5.3 P < .001) and multiparous women (105.5 versus 100.6, −4.93, P < .001) in the multivariate analysis. (Table 4)

Table 4
Table 4:
Effect of Various Factors on Total PISQ-12 Scores

Model B, comparing twin pairs in which both sisters had given birth regardless of delivery mode, revealed that mode of delivery did not significantly affect sexual quality of life according to mean PISQ scores (P = .763). Among twin sister pairs in which both had delivered by vaginal route only (model C), neither episiotomy nor operative delivery was associated with change in sexual quality-of-life score (P = .553). Other factors found to not significantly impact sexual function included weight of largest baby, BMI, and hysterectomy (Table 4).

Multivariable linear regression analyses were also performed on individual questions in the PISQ-12 questionnaire, to gain insight into the effect of parity on specific domains of sexual function. Parity (−1.09, P = .007) and fecal incontinence (−1.74, P = .0001) were predictive of decreased sexual desire. In addition, increasing parity and age were predictive of decreased feelings of excitement at the time of intercourse. Parity did not affect patient reports of dyspareunia, leakage with intercourse, erectile dysfunction, or change in orgasm from 6 months prior.


Sexual function is multidimensional and is affected by psychological, physical, and relational factors.1 The majority of studies evaluating the effects of childbirth on sexual function have focused on immediate physical effects, namely episiotomy,2,10,11 and their conclusions are conflicting. Whereas some studies indicate no difference in short-term sexual function among women who have undergone vaginal delivery versus those delivering by cesarean,12,13 long-term sexual function after these two modes of delivery has not been compared. Even fewer studies have focused on emotional or partner-related aspects of sexual dysfunction specific to childbearing women.12,14 Certainly, for some individuals the psychological strains of parenting may represent a contributing cause for diminished frequency and desire.

Upon evaluating the psychological aspects of sexual function, previous investigators have demonstrated decreased sexual desire and frequency of intercourse within the first year after childbirth.3,15 Few studies, however, have assessed the specific reasons underlying these changes, or how long they persist. Barret et al3 demonstrated that sexual desire initially decreased at 3 months postpartum, and then increased at 6 months postpartum without fully returning to prepartum levels. Their follow-up period, however, did not extend beyond 6 months postpartum. Waterstone et al16 found that common reasons for not reestablishing intercourse after childbirth included lack of a partner, lack of interest, and concern relating to possible genital tenderness or pain. Interestingly, women who suffered severe obstetric morbidity were more likely to list fear of becoming pregnant again as a reason for decreased frequency of intercourse.

We found that decreased sexual desire and excitement were the two sexual function domains most significantly impacted by previous childbirth. Interestingly, mode of delivery (vaginal or cesarean) played no obvious role. In other words, the components of sexual quality of life significantly impacted by childbirth appear to be psychological rather than physical. Previous childbirth did not predispose to pain, anorgasmia, or any other discrete physical complaint within our cohort. We found that neither episiotomy nor mode of delivery significantly impacted the risk of dyspareunia, in agreement with some previous reports.13,17 Hannah et al13 reported, at the 2-year follow-up, that mode of delivery did not affect sexual function in a randomized control trial comparing breech vaginal delivery to breech cesarean section. Similarly, Hartmann et al17 in a meta-analysis comparing routine versus restrictive use of episiotomy, found that routine use of episiotomy did not increase the risk of dyspareunia. In contrast, Signorello et al2 found that at 6 months postpartum the strongest risk factor for dyspareunia was breastfeeding, and instrumental delivery was also a significant predictor of dyspareunia.

Few studies have evaluated partner-related factors in relation to decreased sexual function. Byrd et al12 evaluated pregnant women and their partners at 4 time points during pregnancy, and observed good correlation between the answers of women and their partners. Von Sydow et al14 performed a meta-analysis encompassing most studies relating to sexuality and pregnancy, parenting or childbirth. They found few articles addressing the partners of women who gave birth, and no studies comparing the sexual function of parous women with that of childless women or couples. With respect to “partner issues,” we noted an increase in premature ejaculation among partners of women who gave birth. This finding, however, did not remain significant in the multivariate analysis.

We performed a Medline and MD Consult search for articles in English published between 1966 and October 2005 using the search terms “sexual function,” “sexual dysfunction,” “sexuality,” “childbirth,” “parity,” “parenting,” “twin studies,” and “adoption studies.” To our knowledge, this study is the first to compare sexual function of parous and nonparous women, and the first to evaluate the potential impact of childbirth on sexual function years after the postpartum period. Moreover, the identical twin study design provides “biologic control” over known and unknown genetic determinants, and thus a unique opportunity to identify the impact of environmental predictors (eg, parity and birth mode) on the disease outcome of interest (eg, sexual dysfunction). Using this study design, we demonstrated that parous women have lower self-reported sexual function scores than women without children. In previous studies, lower scores on the PISQ were associated with decreased frequency of intercourse and increased likelihood of restricting sexual intercourse.18,19

Given that parous women report decreased sexual function scores well beyond the postpartum period, the question arises whether these findings are primarily related to physical aftereffects of childbirth, to the psychosocial and relational impact of rearing a child, or both. Although emotional rather than physical domains appeared to be the key factors within our cohort, the design of our study—while providing the first insight into this question—does not allow us to reach definitive conclusions. Future studies comparing the sexual function of women who gave birth with those who adopted children may help to clarify whether physical changes to the pelvic floor play a significant role.

One limitation of our study is that the PISQ-12 has not been validated in women without urinary incontinence or pelvic organ prolapse. The original PISQ had 2 phases of validation. The first took place in women without urinary incontinence or pelvic organ prolapse for generalizability of the instrument. We recognize the lack of validation in a general population as an inherent limitation of our study, but think that the PISQ-12 was the appropriate instrument because over 50% of our sample has self-reported urinary incontinence. It remains unclear whether depression could have played a role in the decreased sexual quality-of-life scores among postpartum women. Indeed, it has been demonstrated that depressed patients tend to report lower scores on the PISQ.5 The vast majority of respondents in our sample, however, were well beyond the postpartum period. Nonetheless, we have included a depression inventory in our survey to be administered at upcoming twin conferences to evaluate general mental health status within this population.

In conclusion, this study of 276 identical twin sisters provides new insight into female sexual dysfunction, and its “environmental” and obstetric determinants. Nulliparous women reported superior sexual function when compared with their biologically identical counterparts, regardless of their age, and irrespective of their mode of delivery. Obstetrical interventions, including episiotomy and forceps, demonstrated no impact on subsequent sexual function for better or worse. Having a child appears to have a lasting impact on sexual function—apparently due to emotional and relational factors, more than to discrete physical injury to the pelvic floor—that extends well beyond the postpartum period.


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© 2006 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.