OBJECTIVE: The objective is to provide guidance for pregnant women, and obstetric care and exercise professionals, on prenatal physical activity. OUTCOMES: The outcomes evaluated were maternal, fetal, or neonatal morbidity or fetal mortality during and following pregnancy. EVIDENCE: Literature was retrieved through searches of Medline, EMBASE, PsycINFO, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Scopus and Web of Science Core Collection, CINAHL Plus with Full-text, Child Development & Adolescent Studies, ERIC, Sport Discus, ClinicalTrials.gov, and the Trip Database from database inception up to January 6, 2017. Primary studies of any design were eligible, except case studies. Results were limited to English, Spanish, or French language materials. Articles related to maternal physical activity during pregnancy reporting on maternal, fetal, or neonatal morbidity or fetal mortality were eligible for inclusion. The quality of evidence was rated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology. VALUES: The Guidelines Consensus Panel solicited feedback from end-users (obstetric care providers, exercise professionals, researchers, policy organizations, and pregnant and postpartum women). The development of this guideline followed the Appraisal of Guidelines for Research Evaluation (AGREE) II instrument. BENEFITS, HARMS, AND COSTS: The benefits of prenatal physical activity are moderate, and no harms were identified; therefore, the difference between desirable and undesirable consequences (net benefit) is expected to be moderate. The majority of stakeholders and end-users indicated that following these recommendations would be feasible, acceptable, and equitable. Following these recommendations is likely to require minimal resources from both individual and health systems perspectives. PREAMBLE: This guideline provide evidence-based recommendations regarding physical activity throughout pregnancy in the promotion of maternal, fetal, and neonatal health. In the absence of contraindications (see later for a detailed list), following this guideline is associated with: (1) fewer newborn complications (i.e., large for gestational age); and (2) maternal health benefits (i.e., decreased risk of preeclampsia, gestational hypertension, gestational diabetes, Caesarean section, instrumental delivery, urinary incontinence, excessive gestational weight gain, and depression; improved blood glucose; decreased total gestational weight gain; and decreased severity of depressive symptoms and lumbopelvic pain). Physical activity is not associated with miscarriage, stillbirth, neonatal death, preterm birth, preterm/prelabour rupture of membranes, neonatal hypoglycemia, low birth weight, birth defects, induction of labour, or birth complications. In general, more physical activity (frequency, duration, and/or volume) is associated with greater benefits. However, evidence was not identified regarding the safety or additional benefit of exercising at levels significantly above the recommendations. Prenatal physical activity should be considered a front-line therapy for reducing the risk of pregnancy complications and enhancing maternal physical and mental health. For pregnant women not currently meeting this guideline, a progressive adjustment toward them is recommended. Previously active women may continue physical activity throughout pregnancy. Women may need to modify physical activity as pregnancy progresses. There may be periods when following the guideline is not possible due to fatigue and/or discomforts of pregnancy; women are encouraged to do what they can and to return to following the recommendations when they are able. This guideline were informed by an extensive systematic review of the literature, expert opinion, end-user consultation and considerations of feasibility, acceptability, costs, and equity. RECOMMENDATIONS: The specific recommendations in this 2019 Canadian Guideline for Physical Activity Throughout Pregnancy are provided below with corresponding statements indicating the quality of the evidence informing the recommendations and the strength of the recommendations (explanations follow). CONTRAINDICATIONS: All pregnant women can participate in physical activity throughout pregnancy with the exception of those who have contraindications (listed below). Women with absolute contraindications may continue their usual activities of daily living but should not participate in more strenuous activities. Women with relative contraindications should discuss the advantages and disadvantages of moderate-to-vigorous intensity physical activity with their obstetric care provider prior to participation. Absolute contraindications to exercise are the following: Relative contraindications to exercise are the following: STRENGTH OF THE RECOMMENDATIONS: The GRADE system was utilized to grade the strength of the recommendations. Recommendations are rated as strong or weak based on the: (1) balance between benefits and harms; (2) overall quality of the evidence; (3) importance of outcomes (i.e., values and preferences of pregnant women); (4) use of resources (i.e., cost); (5) impact on health equity; (6) feasibility, and (7) acceptability. Strong recommendation: Most or all pregnant women will be best served by the recommended course of action. Weak recommendation: Not all pregnant women will be best served by the recommended course of action; there is a need to consider other factors such as the individual's circumstances, preferences, values, resources available, or setting. Consultation with an obstetric care provider may assist in decision-making. QUALITY OF THE EVIDENCE: The quality of the evidence refers to the level of confidence in the evidence and ranges from very low to high. High quality: The Guideline Consensus Panel is very confident that the estimated effect of physical activity on the health outcome is close to the true effect. Moderate quality: The Guideline Consensus Panel is moderately confident in the estimated effect of physical activity on the health outcome; the estimate of the effect is likely to be close to the true effect, but there is a possibility that it is substantially different. Low quality: The Guideline Consensus Panel's confidence in the estimated effect of physical activity on the health outcome is limited; the estimate of the effect may be substantially different from the true effect. Very low quality: The Guideline Consensus Panel has very little confidence in the estimated effect of physical activity on the health outcome; the estimate of the effect is likely to be substantially different from the true effect. This was a weak recommendation because the quality of evidence was low, and the net benefit between women who were physically active and those who were not was small. This was a strong recommendation because, despite low quality evidence supporting physical activity during pregnancy for women categorized as overweight or obese, there was evidence from randomized controlled trials demonstrating an improvement in gestational weight gain and blood glucose. Moderate-intensity physical activity is intense enough to noticeably increase heart rate; a person can talk but not sing during activities of this intensity. Examples of moderate-intensity physical activity include brisk walking, water aerobics, stationary cycling (moderate effort), resistance training, carrying moderate loads, and household chores (e.g., gardening, washing windows). This was a weak recommendation because urinary incontinence was was not rated as a "critical" outcome and the evidence was low quality. This was a weak recommendation because: (1) the quality of evidence was very low; and (2) although harms were investigated there was limited available information to inform the balance of benefits and harms. This recommendation was primarily based on expert opinion.