A Prospective Study of Physical Activity and Fecundability in Women With a History of Pregnancy Loss

Lindsey M. Russo; Brian W. Whitcomb; Sunni L. Mumford; Marquis Hawkins; Rose G. Radin; Karen C. Schliep; Robert M. Silver; Neil J. Perkins; Keewan Kim; Ukpebo R. Omosigho; Daniel L. Kuhr; Tiffany L. Holland; Lindsey A. Sjaarda; Enrique F. Schisterman

Disclosures

Hum Reprod. 2018;33(7):1291-1298. 

In This Article

Abstract and Introduction

Abstract

Study Question: Is physical activity (PA) associated with fecundability in women with a history of prior pregnancy loss?

Summary Answer: Higher fecundability was related to walking among overweight/obese women and to vigorous PA in women overall.

What is Known Already: PA may influence fecundability through altered endocrine function. Studies evaluating this association have primarily utilized Internet-based recruitment and self-report for pregnancy assessment and have yielded conflicting results.

Study Design, Size, Duration: This is a secondary analysis of the Effects of Aspirin in Gestation and Reproduction (EAGeR) trial (2007–2011), a multisite, randomized controlled trial of preconception-initiated low-dose aspirin.

Participants/Materials, Setting, Methods: Healthy women (n = 1214), aged 18–40 and with 1–2 prior pregnancy losses, were recruited from four US medical centers. Participants were followed for up to six menstrual cycles while attempting pregnancy and through pregnancy for those who became pregnant. Time to hCG detected pregnancy was assessed using discrete-time Cox proportional hazard models to estimate fecundability odds ratios (FOR) adjusted for covariates, accounting for left truncation and right censoring.

Main Results and the Role of Chance: The association of walking with fecundability varied significantly by BMI (P-interaction = 0.01). Among overweight/obese women, walking ≥10 min at a time was related to improved fecundability (FOR = 1.82, 95% CI: 1.19, 2.77). In adjusted models, women reporting >4 h/wk of vigorous activity had significantly higher fecundability (FOR = 1.69, 95% CI: 1.24, 2.31) compared to no vigorous activity. Associations of vigorous activity with fecundability were not significantly different by BMI (P-interaction = 0.9). Moderate activity, sitting, and International Physical Activity Questionnaire (IPAQ) categories were not associated with fecundability overall or in BMI-stratified analyses.

Limitations, Reasons for Caution: Some misclassification of PA levels as determined by the short form of the IPAQ is likely to have occurred, and may have led to non-differential misclassification of exposure in our study. Information on diet and change in BMI was not collected and may have contributed to some residual confounding in our results. The generalizability of our results may be limited as our population consisted of women with a history of one or two pregnancy losses.

Wider Implications of the Findings: These findings provide positive evidence for the benefits of PA in women attempting pregnancy, especially for walking among those with higher BMI. Further study is necessary to clarify possible mechanisms through which walking and vigorous activity might affect time-to-pregnancy.

Study Funding/Competing Interest(s): This work was funded by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The authors report no conflicts of interest in this work.

Introduction

The female reproductive system may be influenced by environment, lifestyle, behavior and other factors. Such effects may impact time-to-pregnancy (TTP), which is used to estimate couple fecundability or cycle-specific conception probability (Wilcox, 2010; Buck Louis and Platt, 2011; Sapra et al., 2014). Approximately 60% of couples achieve pregnancy within three menstrual cycles, 80% within six menstrual cycles, and 90% within 12 menstrual cycles, with the remainder meeting the definition for clinical infertility (Wilcox, 2010). Understanding potential modifiable factors for a lengthened TTP may be of particular importance for women with a history of pregnancy loss, since TTP following a loss may be increased (Sapra et al., 2014). Further, the relationship between physical activity (PA) and fecundability has not been evaluated in a population of women with a history of pregnancy loss.

PA has been proposed to influence fecundability through alterations in endocrine function. PA, recognized for maintaining and improving cardiorespiratory and muscular fitness, may represent a widely available strategy for promoting general health (Office of Disease Prevention and Health Promotion, 2017). The '2008 Physical Activity Guidelines for Americans' offer specific guidance for participation in moderate and vigorous-intensity aerobic PA along with muscle-strengthening activity for adults (Office of Disease Prevention and Health Promotion, 2017), and the American College for Obstetrics and Gynecology (ACOG) similarly recommends PA during pregnancy (ACOG Committee Obstetric Practice, 2002). While there are no specific guidelines for women with a history of pregnancy loss who are planning a pregnancy, ACOG offers general information about preconception care, suggesting that overweight women consider losing weight and becoming more physically active prior to pregnancy (Good Health Before Pregnancy: Preconception Care, 2017).

The mechanisms through which increasing PA may impact TTP are unclear. Very high levels of exercise may result in disruption of menstrual cyclicity and increase risk for amenorrhea and subfertility (De Souza et al., 1998; Warren and Perlroth, 2001). Conversely, PA may have beneficial effects on fecundability through reduction of stress and anxiety and/or impacts on lipid profiles and inflammation (Sorensen et al., 2003), though information on thresholds for the amount and intensity of activity to achieve optimal fertility is not known (Warren and Perlroth, 2001; Gudmundsdottir et al., 2009).

To date, few studies have examined the association between PA and conception probability in a population of women not being treated for infertility (Gudmundsdottir et al., 2009; Wise et al., 2012; McKinnon et al., 2016). Results of studies of PA and TTP vary, with some suggesting higher conception probability with moderate intensity activity (Gudmundsdottir et al., 2009), and conflicting results regarding vigorous intensity activity (Wise et al., 2012; McKinnon et al., 2016). Questions remain regarding the association of PA and intensity-specific domains with TTP. Women with a history of pregnancy loss are at risk for protracted subfertility/infertility and may end up requiring clinical care for fertility. For these women, interventions that improve TTP may have significant impact both as an intervention and for making decisions regarding treatment. Clarifying the role and etiology of PA in conception may help to provide recommendations for women with a history of pregnancy loss when attempting pregnancy.

Thus, we aimed to evaluate the relationship between PA and fecundability among a large cohort of reproductive-aged women with a history of pregnancy loss.

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