Can You Build Muscle During Pregnancy? The Truth About Training, Hormones, and Strength While Expecting

Many active women wonder: “If my hormones are high during pregnancy, can I use this time to build more muscle?”

It’s a great question — especially if you love lifting weights or want to stay strong during pregnancy. While your body is in an anabolic state, that anabolic drive is not focused on your biceps, glutes, or quads. Instead, your physiology is working around the clock to grow a healthy baby, prepare for birth, and support breastfeeding.

In this article, I’ll break down how pregnancy hormones, nutrient partitioning, and training limitations affect muscle growth, and what’s realistic when it comes to fitness during pregnancy.

Pregnancy Hormones: Anabolic, But Not for Skeletal Muscle

During pregnancy, levels of estrogen, progesterone, relaxin, and other hormones rise dramatically.

• Estrogen can have mild anabolic effects on muscle, but in pregnancy, its main job is to grow the uterus, increase blood flow, and prepare breast tissue.

• Progesterone actually has a catabolic effect on skeletal muscle — promoting protein breakdown and relaxing muscle tone.

• Relaxin helps loosen ligaments and connective tissues for childbirth, but this also makes joints less stable, which can limit heavy strength training.

• Human placental lactogen (hPL) and prolactin shift your metabolism toward storing nutrients for your baby’s growth and future milk production.

Even though your hormonal profile is “growth-oriented,” the target of that growth is the fetus, placenta, uterus, and breasts — not skeletal muscle.

Nutrient Partitioning: Baby Comes First

To build muscle, you need a caloric surplus, plenty of protein, and progressive overload in training.

During pregnancy, your body prioritizes nutrients for your baby:

• Amino acids, glucose, and fatty acids are preferentially shuttled to the fetus.

• Natural insulin resistance develops in the second and third trimesters, keeping blood sugar higher so more nutrients reach the baby.

• This shift makes it harder for your muscles to get the fuel they need for new growth.

Your body is working like the ultimate nutritionist for your baby — making sure they get first dibs on everything you eat.

Training Limitations During Pregnancy

Building new muscle requires progressively lifting heavier weights or increasing training volume. But pregnancy brings changes that can make this challenging:

• Balance and stability shift as your belly grows and your center of gravity changes.

• Ligament laxity from relaxin increases your risk of injury with heavy lifting.

• Cardiovascular adaptations — like higher resting heart rate and increased blood volume — can reduce exercise tolerance.

• Fatigue, nausea, and sleep changes can make recovery more difficult.

That doesn’t mean you should skip strength training. In fact, moderate resistance exercise is incredibly beneficial for pregnancy — supporting posture, circulation, and even smoother labor.

Metabolic Factors: Why Maintenance Is More Realistic

Pregnancy naturally increases cortisol levels, which can have catabolic effects on muscle tissue. Mild, chronic inflammation also plays a role in supporting the placenta, but it may slightly blunt muscle protein synthesis.

The result? The balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB) tends to stay neutral or slightly negative during pregnancy — meaning your body is more focused on maintaining muscle rather than building new tissue.

Bottom Line: Train Smart, Maintain Strength

Pregnancy is a unique physical state where your body’s “building mode” is entirely focused on your baby. While you’re unlikely to make dramatic muscle gains, you can absolutely:

• Maintain your current muscle mass and strength

• Support your joints and core for a more comfortable pregnancy

• Improve functional strength for labor, delivery, and postpartum recovery

Smart, moderate resistance training during pregnancy benefits both you and your baby — from better posture and reduced back pain to improved recovery after birth.

If you’re looking for a tailored fit pregnancy workout plan, or want expert guidance on prenatal nutrition for strength and energy, I can help you navigate this important time with confidence.

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