Labor is a natural process that results in the birth of one or more infants; "normal" birth begins with the spontaneous onset of labour between 37 and 42 weeks gestation (1). Infants born prior to 37 weeks are considered premature, and those born after 42 weeks are considered postmature. 'Gestational age', a measure of fetal age/maturation, is measured in weeks from the first day of the woman's last menstrual cycle to the date of measurement (2). Although labor is a normal physiological process, it is associated with significant risks of maternal and fetal morbidities, and occurs in three stages (1):
- Commencement of regular painful contractions to full cervical dilatation
- Full cervical dilatation to birth of the infant
- The interval between delivery of the infant and delivery of the placenta and membranes
In the past, it was believed that exercise during pregnancy, particularly the third trimester increased risk of preterm delivery, however, recent research suggests this is not the case. In fact, a randomized controlled trial comparing 70 women engaging in supervised moderate intensity resistance exercise between 12 and 38 weeks of gestation to 70 inactive women suggested there was no difference in gestational age between women who engaged in training and those who did not (3). A study of 131 well-conditioned recreational athletes engaging in aerobic and endurance exercise during pregnancy offered similar results, suggesting women who exercised at or above 50% of their pre-conceptional level had a lower incidence of abdominal and vaginal operative delivery, as well as a shorter period of active labor, with similar rates of pre-term labor to the inactive group (4). Although birthweight tended to be lower in the exercising group, clinical evidence of fetal distress was less frequent in these women, suggesting a beneficial effect of aerobic activity on the course and outcome of labour (4). Exercise during pregnancy has also been associated with shorter hospital stays, fewer maternal and fetal complications, and decreased health-care costs (5).
There is certainly more to be said for the benefits of prenatal exercise on labor outside of demonstrating that it does not cause preterm labour. While research in the area of prenatal exercise and labor is variable, some sources suggest women who exercise while pregnant have lower rates of cesarean delivery as well as lower rates of perceived exertion during labor (5). Additionally, research completed at the Trondheim University Hospital and several outpatient Physiotherapy clinics in Norway suggests not only that pelvic floor training during pregnancy strengthens the pelvic floor muscles, it also prevents urinary incontinence in 1 out of 6 women during pregnancy and 1 in 8 women post-pregnancy (6). In addition, it also suggests that intensive training of the pelvic floor muscles during pregnancy facilitates labour and may also prevent a prolonged second stage of labor (active pushing) in as many as 1 in 8 women (6).
Finally, the impact of prenatal exercise on stress, mood and birth outcomes cannot be overlooked. Recent research suggests that stress and negative mood during pregnancy increases the risk for both postpartum mood issues, as well as poor childbirth outcomes such as earlier birth, younger gestation age and lower birthweight (7,8). A recent study of pregnancy-specific stress and birth outcomes linked high levels of pregnancy-specific stress to pre-term delivery as well as low birthweight. In this same study, prenatal exercise and healthy eating were inversely related to pregnancy-specific stress (8).
While all of this information is promising, the main theme running through this series has been individuality. Each woman will both engage in and respond to exercise in her own way. Please note that all exercise performed in the aforementioned studies was supervised to ensure both appropriateness as well as safety for both mum and baby. Obstetrics Nurse Trese Zannis expands on this concept based on her experience in the Sunnybrook Labour and Delivery rooms:
“My experience in the birthing unit at SHSC has allowed me to work with women of varying backgrounds, socioeconomic statuses, and ages; providing one-to-one care in such a setting allows for the formation of a bond between the patient and myself. I have had patients that range from athletes to the women who enjoy walking in their spare time. Even though each patient comes with their own exercise background, there has been one commonality between them all: physical activity in pregnancy (when done under the supervision of a doctor and interdisciplinary team) has many benefits. My experiences with exercise in pregnancy and how it can be beneficial in the labor and delivery period are all anecdotal…I once had a patient who was a competitive runner tell me that continuing to be active in her pregnancy allowed her to cope better with the labor experience and that she had an easier time healing in the postpartum period. I have also had women who continued to do such things as: yoga, walking, and weight lifting tell me that not only was the pregnancy more manageable (with regards to less fatigue and more energy), but that they felt more prepared for the labor and delivery process because they were used to pushing their bodies in some capacity when they exercised. So while exercise posits a plethora of benefits, one should always consult their physician and interdisciplinary team of health care providers before starting or continuing an exercise regime in pregnancy.”
-Trese Zannis R.N, Obstetrics Nurse at Sunnybrook Health Sciences Centre
- Narayan R, Hyett J. Labor and Delivery. In: Women's Health: A Core Curriculum. Editors Jason Abbott, Lucy Bowyer, Martha Finn. Elsevier Health Sciences (2013) pp 184-201.
- U.S. National Library of Medicine. Gestational Age. Updated 12/4/2013. Available at: http://www.nlm.nih.gov/medlineplus/ency/article/002367.htm
- Barakat R, Stirling J R, Lucia A. Does exercise training during pregnancy affect gestational age? A randomized controlled trial. British Journal of Sports Medicine:(42) 2008 pp 674-78.
- Clapp J. The house of labor after endurance exercise during pregnancy. American Journal of Obstetrics and Gynecology. 1990. 163(6): 1799-1805.
- Effects of maternal exercise on labour and delivery. In: Physiology of Prenatal Exercise and Fetal Development. May, L.E. SpringerBriefs in Physiology. 2012 (VII). DOI: 10.1007/978-1-4614-3408-5_2
- Salvesen K, Morkved S. Randomized controlled trial of pelvic floor muscle training during pregnancy. British Journal of Medicine. 2004 Vol 329: pp 378-380.
- Vieten C, Astin J. Effects of a mindfulness-based intervention during pregnancy on prenatal stress and mood: results of a pilot study. Archives of Women's Mental Health. 2008 (11): 67-74. DOI 10.1007/s00737-008-0214-3
- Lobel M, Cannella D L, Graham J E, DeVincent C, Schneider J & Meyer B A. Pregnancy-specific stress, prenatal health behaviors, and birth outcomes. Health Psychology. 2008. 27(5): pp 604-615.