Pregnancy is one of the most physiologically demanding periods the human body can experience.

Almost every major system changes:

• Hormones shift dramatically
• Blood volume increases
• Breathing mechanics adapt
• Ligaments become more lax
• Metabolic demands rise
• The abdominal wall stretches
• The pelvic floor carries increasing pressure

Modern research shows that for most uncomplicated pregnancies, appropriately adapted exercise is not only safe — it is beneficial.¹

But pregnancy training should never be random. The strategy must evolve with the physiology.

1. Cardiovascular Changes During Pregnancy

One of the earliest and most significant adaptations is cardiovascular.

During pregnancy:

• Blood volume increases approximately 30–50%
• Cardiac output rises significantly
• Resting heart rate increases
• Oxygen demand becomes higher

This is why many pregnant women feel:

• Out of breath more easily
• Hotter during exercise
• Fatigued faster than usual

These responses are often normal physiological adaptations — not necessarily loss of fitness.

2. Respiratory & Breathing Changes

As the uterus expands upward, the diaphragm gradually shifts position.

The rib cage widens and breathing mechanics change.

Many women notice:

• Shallower breathing
• Difficulty taking deep breaths
• Reduced tolerance for intense cardio

At the same time, oxygen consumption increases to support both mother and baby.²

This is one reason breath coordination becomes extremely important during prenatal training.

3. Hormonal Changes & Joint Stability

Pregnancy hormones significantly influence movement.

The most discussed is relaxin, which contributes to increased ligament laxity and pelvic adaptation.

This does not mean women become “fragile.”

But it does mean:

• Joint stability may change
• Overstretching becomes less beneficial
• Controlled movement becomes more important
• Balance and coordination may feel different

Progesterone and estrogen also influence:

• Fluid retention
• Temperature regulation
• Fat storage
• Energy levels

4. What Happens to the Core & Abdominal Wall?

As the baby grows, the abdominal wall stretches to accommodate expansion.

The linea alba — connective tissue between the abdominal muscles — also stretches. This can contribute to diastasis recti, a separation between the rectus abdominis muscles.

Important nuance:

Some degree of abdominal separation is normal during pregnancy.

The goal is not fear. The goal is pressure management.

This is why prenatal training increasingly focuses on:

• Breathing mechanics
• Core coordination
• Pelvic floor integration
• Reducing excessive intra-abdominal pressure

5. Pelvic Floor Changes

The pelvic floor experiences increasing pressure throughout pregnancy due to:

• Growing fetal weight
• Changes in posture
• Fluid and tissue changes
• Breathing adaptations

Modern pelvic-floor research emphasizes that these muscles must both:

• Contract effectively
• Relax and lengthen when necessary

Pregnancy training is moving away from endless isolated “Kegels” toward integrated breathing and pressure management strategies.³

6. Metabolic Changes & Calorie Needs

Pregnancy increases energy requirements — but not as dramatically as social media often suggests.

The phrase “eat for two” is biologically misleading.

Evidence-based estimated calorie increases are approximately:

Needs vary depending on:

• Pre-pregnancy body size
• Activity level
• Twin pregnancies
• Metabolic health

7. Insulin Resistance, Hunger & Pregnancy Cravings

One of the most misunderstood changes during pregnancy is insulin resistance.

Many women notice:

• Stronger hunger
• More cravings for carbohydrates or sweets
• Energy crashes
• Feeling shaky if meals are delayed

This is not simply lack of discipline.

Pregnancy naturally creates a state of progressive insulin resistance, especially during the second and third trimester.⁴

Biologically, this happens because the body is trying to ensure a stable glucose supply for the growing baby.

Hormones produced by the placenta alter insulin sensitivity so that more glucose remains available in circulation.

This is a normal adaptation — but in some women, especially with genetic predisposition, higher body fat levels, or pre-existing metabolic dysfunction, insulin resistance may become excessive and contribute to gestational diabetes.

Why Do Cravings Happen?

Pregnancy cravings are influenced by multiple factors:

• Blood sugar fluctuations
• Increased energy needs
• Hormonal shifts
• Changes in dopamine and reward signaling
• Emotional and psychological changes

Many women become more sensitive to drops in blood sugar during pregnancy, which may increase cravings for quick energy sources like sweets or refined carbohydrates.

Sleep deprivation and chronic stress may intensify these cravings further because cortisol also affects appetite regulation.

Can Exercise Help?

Yes. Moderate movement and resistance training improve insulin sensitivity and glucose regulation during pregnancy.⁵

Walking after meals, strength training, and balanced meals with adequate protein and fiber may help stabilize energy and reduce extreme blood sugar fluctuations.

The goal is not rigid control or fear around food.

Pregnancy is a period of increased biological demand. The objective is supporting metabolism intelligently while respecting the body’s changing needs.

8. Protein Needs Increase Too

Protein requirements rise during pregnancy because the body is building:

• Fetal tissue
• Placenta
• Maternal tissue
• Expanded blood volume

Emerging evidence suggests many active pregnant women may benefit from approximately:

1.2–1.6 g protein/kg bodyweight/day⁶

Protein becomes especially important for maintaining muscle tissue during pregnancy.

9. Weight Gain During Pregnancy

Weight gain during pregnancy is not only fat gain.

It includes:

• Baby weight
• Placenta
• Amniotic fluid
• Blood volume
• Breast tissue
• Fluid retention

Healthy weight gain varies significantly depending on pre-pregnancy BMI and individual physiology.

This is why pregnancy should not be treated as a “body composition challenge.”

10. Training by Trimester

First Trimester

Often characterized by:

• Fatigue
• Nausea
• Hormonal instability
• Lower recovery tolerance

Some women continue training normally with adjustments. Others need reduced intensity temporarily.

Second Trimester

Often the “best-feeling” phase for many women.

Energy may improve, making this a good period for:

• Strength maintenance
• Walking
• Mobility work
• Postural training

Third Trimester

Typically involves:

• Higher pelvic pressure
• Breathing limitations
• Reduced balance
• More fatigue

Training usually shifts toward movement quality, circulation, breathing, and comfort.

11. Final Thoughts

Pregnancy is not weakness. It is adaptation on a massive biological scale.

For most healthy pregnancies, movement remains beneficial — but training must evolve with the body instead of fighting against it.

The goal is not “bouncing back.”

The goal is supporting strength, resilience, confidence, and recovery through one of the most transformative periods of life.

As always, feel free to leave thoughts, experiences, or new research in the comments. These articles are open to learning and evolving 🤍

References

1. ACOG Committee Opinion No. 804: Physical Activity and Exercise During Pregnancy and the Postpartum Period. Obstetrics & Gynecology. 2020.
2. Artal R, O'Toole M. Exercise during pregnancy. British Journal of Sports Medicine. 2003.
3. Bø K, Hilde G. Pelvic floor muscle function during pregnancy and postpartum. Physiotherapy. 2023.
4. Barbour LA et al. Cellular mechanisms for insulin resistance in normal pregnancy and gestational diabetes. Diabetes Care. 2007.
5. Davenport MH et al. Prenatal exercise improves glycemic control and reduces gestational diabetes risk. British Journal of Sports Medicine. 2018.
6. Stephens TV et al. Protein requirements during pregnancy. Current Opinion in Clinical Nutrition & Metabolic Care. 2015.