Prenatal Exercise and Cardiovascular Health (PEACH)

Maintenance of a healthy pregnancy depends on an appropriate adaptation and responsiveness of blood vessels, to ensure appropriate blood flow to the fetus during everyday stressors. Previous work by the investigators has demonstrated that during pregnancy, the part of the nervous system responsible for cardiovascular function (the sympathetic nervous system) is hyperactive. The investigators also know that in women who develop high blood pressure during pregnancy that sympathetic nervous system activity is even higher. Yet, very little is known about why this occurs and how this might be affected.

Pregnant women are encouraged to be active, yet, less than 15% of women perform sufficient exercise to meet current guidelines. This is important because hyperactivity of the sympathetic nervous system is observed in other inactive populations and has been linked to adverse cardiovascular health outcomes including hypertension, atherosclerosis, heart attack, and stroke. Indeed, in 2011, the American Heart Association stated that inactivity was a risk factor as potent as cigarette smoking for the development of future cardiovascular disease in women.

The investigators' work and others have demonstrated that exercise during pregnancy is beneficial for both the mom and baby; however, the effect of prenatal exercise on neurovascular function is not known. If exercise is effective in controlling the increase in sympathetic activity that occurs during pregnancy, or its effects on the cardiovascular system, this may help prevent the development of high blood pressure or other cardiovascular problems during pregnancy.

The objectives of this study are to: 1) examine the impact of exercise on sympathetic and vascular function during pregnancy; 2) examine the role of endothelial function on the vascular effects of exercise during pregnancy.

Study design:

100 women (\>18yrs) will be recruited in the first or second trimester (\<20 wks). Women with multiple pregnancies will be excluded. Eligible women will be randomized between an aerobic exercise intervention (EXER) or no intervention (CTRL).

Initial testing will take place between 16-20 weeks of pregnancy. Following initial baseline testing, women will be randomly assigned to an exercise intervention or no intervention. Women will receive an opaque sequentially numbered envelop with their allocation. Allocation will be determined using a randomly generated allocation sequence by an individual not associated with the research study. The intervention will consist of aerobic exercise equivalent to 50-70% of heart rate reserve, 3-4 times per week until the end of the study (34-36 weeks). For initial baseline testing (16-20 weeks) and at the end of the intervention (34-36 weeks), participants will visit the laboratory twice

On Day 1, participants will complete a peak exercise test on the treadmill or bike to volitional fatigue to measures fitness and cardiovascular/cerebrovascular responses to exercise.

On Day 2 Participants will arrive fasted (12 hrs) and blood samples will be collected. Anthropometrics, personal/familial history of hypertension and pregnancy complications will be recorded. Following a standardized breakfast, participants will undergo an assessment of reflex neurovascular control including a cold pressor test, flow mediated dilation and end expiratory voluntary breath hold. Muscle sympathetic nerve activity, ultrasound (blood flow and diameter of brachial, femoral and carotid arteries), blood pressure, heart rate and respiratory variables will be measured.

OUTCOME/IMPACT

Pregnancy is a stress-test for life; with women who develop complications during pregnancy having a higher risk for cardiovascular disease later in life. Exercise is well known to prevent cardiovascular disease through improvements in endothelial function and the sympathetic nervous system. Whether this improvements is also seen in pregnancy remains to be seen.

Eligibility Criteria:
Inclusion Criteria:

* \>18 years old
* singleton pregnancy
* cleared to exercise by health care provider using Par Med X for Pregnancy (CSEP)

Exclusion Criteria:

* multiple gestation
* absolute contraindication to exercise (CSEP)
* \<18 years old
* develops any contraindication during intervention