Heart Rate in Pregnancy

Cardiovascular Adaptations in Pregnancy

Pregnancy determines a whole series of hemodynamic changes, necessary to satisfy the nutritional needs of the fetus. These include the increase in circulating blood volume, stroke volume and heart rate; the latter, in particular, begins to rise from the fourth week of conception and continues to grow throughout the rest of the pregnancy. In view of the birth, the heart rate will have risen by about 15 beats per minute with respect to the pregravidici values, while one fifth of the maternal circulating blood will constantly flow to the uterus.

The expansion of the volume (amount of circulating blood) can be quantified as 30-50% compared to the pregravidici values. To pump the increased quantities of blood into the circulation, the heart has two possibilities: to increase its speed of contraction (heart rate) or increase the amount of blood expelled at each contraction (stroke volume). Of course, both mechanisms are exploited.

With the same effort, during physical exercise, stroke volume and heart rate increase more in pregnant women than in non-pregnant women.

During labor, the cardiac output increases by a further 10%, while after the birth, the frequency and pulse volume decrease first rapidly, then more gradually; pregravid levels will be reached approximately 6 weeks after delivery.

Normal values

During a normal pregnancy, the heart rate passes indicatively from the canonical 70 beats per minute to 80-90 bpm.

Values ​​during physical activity

During pregnancy high intensity workouts are strongly advised against, to avoid unnecessary risks of fetal hypoxia (decrease of oxygen to the fetus due to the high metabolic demands of the maternal body committed to supporting exhausting efforts).

More than recommending rigid values ​​regarding ideal heart rates, to be respected during training, it is certainly better to personalize the expected intensity level to the maximum. We therefore recommend:

train at heart rates between 50 and 70% of HRmax, or train at a level of effort between the tenth and fifteenth points on the Borg scale.