Pregnancy, part 1: Physiological changes

27/02/2024 Par Stéphanie Guinois-Côté, physiotherapist in perineal rehabilitation

Part I provides information on the many changes taking place in the body during pregnancy. During this period, a woman’s body undergoes many changes. It’s important for women to understand these changes so they can be as in control as possible. This section focuses on women’s health and well-being during this process. For additional information on pregnancy, see Part II.

It’s important to remember that the following information is a brief summary of each topic covered. It is strongly recommended that you be evaluated by a perineal rehabilitation physiotherapist for your questions and for a program specific to your pregnancy/post-partum.

During pregnancy, a woman’s body undergoes many changes. Most of these changes are due to hormone secretion. Each hormone secreted has an impact on the general functioning of the human body. Here’s a summary of the effects of pregnancy on the body’s systems.

The cardiovascular system

The cardiovascular system undergoes the most changes early in pregnancy. These changes are also most marked in women. They are mainly due to the fetus’ need for oxygen and nutrients. During pregnancy, the main changes to this system are as follows:

↑ of blood volume from weeks 6-8
- Up to 45-50% between weeks 30 and 34
Change in heart positioning and remodeling
↑ of cardiac output by about 50%
- ↑ of resting heart rate by 15-20 bpm
↑ concentration of clotting factors
- Be alert to signs of thromboembolism
Presence of edema, varicosities and varicose veins
- Especially in legs, vulva and vagina
- Hemorrhoids more frequent

Regulation of body temperature (thermoregulation)

Body temperature during pregnancy is important, especially in the 35-42 days after the last menstrual period. It is during this period that the formation of the neural tube in the fetus occurs. There may be an increased risk of malformation if body temperature exceeds 39 ℃. Fortunately, thermoregulation is improved during pregnancy. So you’ll notice an increase in sweating, which helps to evacuate heat.

Here are a few causes of hyperthermia (pronounced rise in body temperature):

Fever
Long-term vigorous exercise in a hot environment
Hot yoga
Saunas and whirlpool baths/spas (>30min)
Heated blankets

The respiratory system

There will also be a reorganization of the shape of the rib cage. There will be an increase in thoracic diameter, an increase in the infracostal angle, and an increase in the mobility of the rib cage joints. The latter can lead to pain in the ribs and sternum. Other changes will appear:

Elevation of the diaphragm due to fetal growth
Decreased lung capacity due to compression of the diaphragm by the uterus
Decreased backward movement of the ribs

All these factors affect the respiratory pattern. It is therefore normal to feel out of breath more often and more quickly.

The gastrointestinal system

A general decrease in peristalsis (involuntary contractions of the walls of the digestive tract, allowing food to be broken down and moved) is noted during pregnancy. This has a direct impact on digestion. As food passes through the digestive system more slowly, changes can be noted in this area.

Here are some common symptoms related to the digestive system during pregnancy:

Nausea and vomiting
Heartburn, reflux
Gallstones
Constipation
Stool consistency = hard and dry

These are mainly due to reduced movement of food through the digestive tract, sphincter incompetence and general muscle relaxation.

To help stool movement, try to eat fibre-rich foods, move regularly and drink the recommended amount of water (1.5-2L) every day.

The urinary system

During pregnancy, it’s normal to have to go to the bathroom more often than usual. This increase can be felt as early as the first few months of pregnancy. The last trimester, however, is when the frequency is greatly increased. This is because the uterus applies considerable pressure to the bladder, making it less able to stretch to accommodate the urine. Frequency is also increased by an increase in blood volume, causing the kidneys to filter more urine. It is also possible to experience symptoms of urinary incontinence. Incontinence can be caused by:

Increased amount of urine remaining in the bladder after urination
Weakening of the pelvic floor
Excessive pressure on the bladder

However, urinary incontinence is not a normal symptom of pregnancy. Advice and exercises can be applied to remedy the problem.

The musculoskeletal system

A general increase in joint laxity and mobility will occur. This is mainly due to the secretion of the following hormones: progesterone, estrogen, endogenous cortisols and relaxin. This laxity may persist for up to 6 months post-partum, especially if you are breast-feeding. Decreased muscle control in the lumbar and pelvic region may also occur. Here are some of the effects of these hormones:

Postural changes (mainly due to the growing fetus)
Joint laxity and hypermobility
Decreased abdominal competence
Weakened pelvic floor

For more information, advice or any other question concerning the pelvic floor, don’t hesitate to book a free 15-minute telephone consultation or make an appointment with Stéphanie, our perineal rehabilitation physiotherapist at Clinique de La Prairie.