Physical Activity Recommendations

Current physical activity recommendations are informed by general advice for healthy adults with the American College of Obstetricians and Gynecologists advising 20–30minutes of moderate PA of moderate intensity on most or all days of the week in the absence of contraindications. Contraindications to exercise include heart or lung disease, incompetent cervix, multiple gestation with risk of premature labor, persistent second- or third-trimester bleeding, placenta previa after 26 weeks gestation and preeclampsia. With a safe upper level of exercise intensity yet to be established, PA that can be easily quantified to monitor perceived intensity and exertion is recommended, including the use of perceived exertion scales, which may be more practical than continuous heart rate monitoring in general populations, A score between 13–14 out of 20 on the Borg’s Rating of Perceived Exertion scale is indicative of moderate intensity.pregnancy activity

Overall, there is little evidence to suggest that regular moderate intensity PA throughout pregnancy is detrimental to foetal development or raises maternal core body temperature sufficiently to impose risk. Therefore, in normal pregnancies, and when PA is at recommended levels, there is general agreement that the benefits of exercise during pregnancy far outweigh any risks to themother or fetus, with guidelines advising adequatehydration and PA in cool environments with participation in contact or higher risk sports restricted. Despite the documented ‘teachablemoment’ of pregnancy with increased motivation for healthy lifestyle behaviors, pregnancy is usually associated with decreased levels of PA. Concerns about safety and potential adverse effects on the developing fetus, as well as changing body shape, tiredness and time constraints are themost commonly cited barriers to regular activity during pregnancy.

Gestational Weight Gain

Increased gestational weight gain (GWG) is a risk factor for antenatal complications. Exacerbating risk is pre-existing overweight and obesity which in itself is an established risk factor for maternal complications including miscarriage, hypertension, gestational diabetes mellitus (GDM) and caesarean delivery as well as large-for-gestational age (LGA) neonates. Excess weight gain in early to mid pregnancy is particularly important, as maternal fat accretion peaks at 30 weeks gestation and directly correlates with total GWG and long-termobesity development.

A recent Cochrane review of 13 RCT exercise intervention studies (n ¼ 10 supervised exercise intervention, n ¼ 3 unsupervised self-directed exercise) supports the role of PA for the prevention of excess GWG, reporting a 21% (11–31% range overall) reduction in risk compared with standard care. On further analysis, the most protective benefit of PA was in women with a healthy BMI, with a 31% reduced risk of excessive GWG, compared with a 16% reduced risk when obese women only were included (23% reduced risk in the total sample). Additionally, in 3 studies reporting total GWG (n ¼ 1134 participants) a significantmean reduction of 1.35kg overall (95% CI -1.80, -0.89) was noted. Encouragingly, on analysis of the total sample, this review found that increased PA was as effective as dietary intervention for reducing risk of excessive GWG, with a 23% reduced risk noted with a low glycaemic load diet and a 14% reduction with diet and PA counselling. Substantial heterogeneity in the dietary intervention studies (n ¼ 36) prevented pooling of data, however most reported no benefit on risk of excessiveGWG; only 5 of 36 studies noted a significant effect. The most benefit in risk of excessive GWG was found in studies that included both supervised exercise training and dietary intervention, with a 29% reduction overall. These findings are supported by a previous systematic review with comparable results.

Prevention and Treatment of Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM), defined as glucose intolerance with onset or first recognition during pregnancy, is closely related to obesity, IR and T2DM in women and its prevalence has dramatically increased in parallel with recent rises in obesity rates in women. Modifiable and unmodifiable factors drive GDM risk, with development associated with a progressive rise in insulin resistance (IR) with advancing pregnancy. Prevalence varies depending on the population studied and diagnostic criteria applied, however current estimates indicate GDM affects 6–14% of pregnancies.gestational diabetes

GDM increases neonatal and maternal risks, including LGA neonates, neonatal hypoglycaemia andmorbidity, as well as increased rates of delivery by caesarean section. Long term, maternal progression to T2DM occurs in 15-70% of women with a history of GDM and offspring are at an increased risk of obesity development as well as T2DM. A 2015 systematic review of 10 RCT studies comparing increased PA as a stand-alone intervention with standard care in 3401 participants of whom 275 developed GDM estimated a 28% lower risk in the development of GDMon meta-analysis (RR 0.72, 95% CI 0.58–0.91, p < 0.005). The majority of studies enrolled women in the first or early second trimester and included women of all BMI levels with the exception of three studies targeting overweight or obese women. These studies involved aerobic PAof varying types, with the majority involving 3–4 exercise sessions of 45–60 minutes duration per week. Four studies included a resistance training component. In pregnancies complicated by GDM, treatment centres on achieving glucose control through lifestyle change as a first line approach. The potential theoretical use of PA as an adjunctive therapy for GDMtreatment is promising due to its effects on glucose uptake and utilization. Yet despite this, evidence for the role of exercise in the treatment of GDM is inconclusive.

A 2006 Cochrane review of four trials, with a combined 114 GDM cases, reported no significant difference between combined exercise and diet therapy intervention and minimal or dietary therapy alone on glucose control, insulin prescription, or neonatal and maternal outcomes. The included studies commenced exercise in the third trimester for a minimumof 6 weeks duration, 3–4 times weekly at moderate intensity (50–70% VO2 max). With insufficient evidence on the role of exercise in GDM treatment, advice regarding the optimal type, frequency, intensity and duration of exercise required for blood glucose control remains unclear. Larger, high quality studies are required to elucidate the independent role of exercise in treating GDM.

Prevention and Treatment of Hypertension and Pre-Eclampsia

Hypertensive disorders of pregnancy are one of the most common maternal complications, affecting 10% of pregnant women. Risk factors mirror those in the general population and include advanced maternal age, ethnicity, family history of hypertension and increased CVD risk factors as well as a sedentary lifestyle. Chronic, pre-existing hypertension (prior to 20 weeks gestation) and gestational hypertension (transient hypertensionmanifesting after 20weeks gestation and resolving by 6 weeks postpartum), affects 5–8% of women and is characterized by a systolic blood pressure (BP) 140mmHg and/or a diastolic BP 90mmHg.

Preeclampsia is a multisystemdisorder of increased severity on the spectrumof hypertensive disorders, affecting 5–8% of pregnancies and is typically characterized by hypertension and proteinuria manifesting in the second half of pregnancy. Despite the protective role of PA in hypertension in the general population, its role in preventing preeclampsia is yet to be fully elucidated.pre eclamsia

Systematic reviews in the area report contradictory findings, potentially owing to methodological differences, including criteria for included studies. A Cochrane review of two small RCT studies in 45 women reported insufficient power to detect any beneficial role of PA in the prevention of pre-eclampsia in women at increased risk prior to, or in, early pregnancy. These studies included moderate intensity exercise at least 3 times per week of 30–45 minutes duration, from18 weeks gestation for 10 weeks or 34 weeks gestation until term. Yet a second recent systematic review including casecontrol and cohort studies only reported an inverse relationship between increasing PA before or during early pregnancy and reduced risk of preeclampsia. Using prospective cohort studies, the authors report a 35% relative risk (RR) reduction in women exercising in the highest category prior to pregnancy (4 studies, n ¼ 9733 participants of whom 420 developed preeclampsia) and a 18% RR reduction with high levels of PA in early pregnancy (7 studies, n ¼ 162,558 participants of which n ¼ 5077 developed pre-eclampsia). The meta-analysis also included a dose–response analysis of PA pre-pregnancy and risk of pre-eclampsia and reported a non-linear trendwith themost protective benefits found with between 5–6 hours of activity per week, with a 40% reduction in risk, overall. However, as the review included only observational studies, with no reported methodological quality analysis, results should be interpreted with caution and further research is required.

Labor and Delivery

In theory, the stronger and more physically fit awomen is at term, the better her ability to cope with labor and delivery. However limited evidence exists that PA during pregnancy improves labor, labor duration and perceived ease of delivery. There is evidence from recent prospective cohort studies that sufficiently active pregnant women have a lower risk of medical intervention during delivery, including caesarean delivery. Cultural factors have more effect than PA on procedures such as episiotomy, epidural induction of labor and method of delivery.

Neonatal Outcomes

Although some observational studies have reported associations between PA, gestational age and neonatal birth weight, the effects are extremely small with the general consensus being that PA of light, moderate or vigorous intensity does not affect infant birth weight when appropriate confounding factors are controlled for. A Cochrane review of 14 intervention studies with over 1000 women reported no significant effects of exercise on birthweight. Ameta-analysis reported had 31% less riskof having a largebaby (>90th percentile)with regular PA, and that babies of exercising women were 31 g lighter than non- exercising women. Data from a large Norwegian study found lower adjusted odds (0.76–0.91) for pre-termbirth among exercising women, compared with non-exercising women, however the mean difference was only 1–2 days.

Lactation and Breastfeeding

Moderate to vigorous PA does not negatively affect breast milk composition and volume, provided adequate food and fluid intake is maintained, with the caloric cost of breast feeding estimated to be 600 kcal/day. Recommendations include breastfeeding prior to exercise, postponing breast feeding to one hour after exercise, or expressing if required, in cases where infants are unsettled with feeding immediately after the mother exercises.

Postpartum Weight Retention

With 60% of women exceeding IOM guidelines for GWG, postpartum weight retention is common with up to 20% of new mothers retaining 5 kg or more one year postpartum, driving long-termhealth risk. PA in the postpartumperiod is important for weight maintenance as well as other health benefits, however may not induce sufficient weight loss as a standalone therapy. While a 2007 Cochrane review of two studies with 53 participants overall found an insignificant change in postpartumweight following exercise intervention of -0.10kg (95% CI -1.90, 1.71) compared with usual care, a recent review of six studies found a significant weight loss of -1.63kg (95% CI -2.16, -1.10). Both these and other reviews, have noted a greater effect on weight loss in intervention studies that included a dietary component, with mean changes in weight of between 2–4.3 kg. More intensive dietary interventions and more structured activity programs incorporating HR monitors or pedometers, were associated with higher weight loss.baby training

Postpartum Depression and Quality of Life

Postpartum depression (PPD) is a prevalent condition affecting 10–15% of women within the first year of birth. Severity and duration varies, however approximately half of all cases occur within the first 12 weeks following birth and severitymay be exacerbated by the added demands placed on new mothers following birth. PA and/or exercise interventions for the prevention or treatment of PPD are limited, with fewhigh quality RCT studies, small sample sizes and high variability in time from delivery at recruitment.

Data from a recent meta-analysis of 6 exercise intervention studieswithin 12 months postpartum reported a weighted mean reduction in Edinburgh Postnatal Depression Score (EPDS) of 2.22 (95% CI 0.48, 3.96), with this change remaining below the clinical significance indication of a 4 unit change, increasing equivocality. Studies comprised either structured exercise classes (n ¼ 4) or provided tailored exercise advice (n ¼ 4). Overall, the meta-analysis supported a moderate effect of exercise for the treatment of PPD. Walking groups may also be beneficial for reducing PPD with data from two small RCT studies of between 20–24 women reporting a 59–65% reduction in scores following a 12 week intervention of 2–3 walking sessions per week. These results are supported by cohort studies showing comparable results with low-moderate and vigorous exercise interventions commencing both in pregnancy or the postpartum period. Although studies evaluating causation between increased PA and reduction in indicators of PPD are needed, PA may potentially act to elevate mood, improve self-efficacy and sleeping patterns, alleviate stress and increase coping strategies. Women report a greater sense of well-being and health related QoL with postpartum exercise. As preconception and antenatal exercise are associated with reduced PPD risk following pregnancy, women should be encouraged to engage in regular activity to enhance potential benefits on mental well-being post-pregnancy.

Conclusion

Women of reproductive age are a high risk group for progression to obesity; increasing the risk of morbidity and contributing to the global economic health burden. Preconception, pregnancy and the early postpartumperiod represent opportunewindows to engage women in regular PA to optimize health and prevent weight gain with added potential to transfer behavior change more broadly to children and families. Yet, many reproductive aged women do not meet PA guidelines preconception, with pregnancy and the postpartum period marking further PA decline, warranting public health efforts in this population.

To date, few studies have evaluated PA as a standalone therapy and key methodological gaps necessitate further research. Large, comparative, high-quality studies, addressing barriers to exercise with objective PAmeasurement and with reporting of compliance and adherence are now needed to clarify the optimal type, frequency, duration and intensity of PA required for beneficial health outcomes for women, during preconception, pregnancy and postpartum.