The hip thrust is a popular and effective exercise that primarily targets the gluteus maximus. This movement involves placing the upper back against a bench and using the hips to lift a barbell or other weight, engaging the hamstrings and quadriceps as secondary muscles. Many active individuals question whether certain movements, particularly those involving heavy lifting or supine positioning, could potentially cause a miscarriage. This article provides evidence-based information regarding the safety of the hip thrust exercise throughout pregnancy.
Understanding Miscarriage Causes and Timing
The concern that physical activity might lead to pregnancy loss is common, but it is important to understand the typical causes and timing of miscarriage. A miscarriage is defined as the spontaneous loss of a pregnancy before 20 weeks’ gestation, with the vast majority occurring in the first trimester. It is estimated that approximately 50% to 70% of first-trimester miscarriages are due to chromosomal abnormalities in the developing fetus.
These chromosomal issues, such as having an extra or missing chromosome, are genetic errors that occur spontaneously and are fundamentally incompatible with continued development. Common examples include Trisomy 16 and Monosomy X, which are often lethal to the embryo. These developmental failures are biological events that moderate physical activity, lifting, or external strain cannot prevent or cause.
The uterus and fetus are protected within the pelvis during the early weeks, shielded by the pelvic bones and amniotic fluid. Therefore, the scientific consensus is that moderate exercise, including strength training, is not a primary cause of miscarriage in a healthy, uncomplicated pregnancy. Focusing on these biological realities can help alleviate the fear that a workout might be the cause of an early pregnancy loss.
Evaluating the Risk of Uterine Pressure During Hip Thrusts
The hip thrust exercise, when performed correctly, is a horizontal movement that focuses on hip extension, not vertical pressure on the abdomen in the early stages of pregnancy. In the first trimester, the uterus is small and contained within the pelvic bowl. This makes it physically impossible for the external force of a barbell across the hips to create undue internal pressure on the developing fetus. This exercise primarily recruits the large muscles of the posterior chain, which are safely accessible throughout this initial period.
A common concern relates to the supine position, or lying flat on the back, which is generally advised against later in pregnancy. This advice is not related to miscarriage risk, but rather to a condition known as Aortocaval Compression Syndrome, or supine hypotensive syndrome. After approximately 20 to 24 weeks of gestation, the growing size and weight of the uterus can compress the inferior vena cava, a major vein that returns blood to the heart.
This compression can reduce blood flow back to the mother’s heart, potentially causing a drop in blood pressure and reduced blood flow to the placenta. Symptoms often include dizziness, pallor, or nausea, and the condition is usually temporary, resolving quickly by shifting to a side-lying position. Because the risk is related to the size of the uterus, which becomes significant only in the second half of pregnancy, the hip thrust performed in the first trimester does not pose this risk. Based on current medical understanding, hip thrusts performed with appropriate modifications and weight are not linked to an increased risk of miscarriage.
Adapting Lower Body Strength Training During Pregnancy
While hip thrusts are safe in the early stages, modifications become necessary as the pregnancy progresses to ensure comfort and safety. As the abdomen grows, the positioning of the barbell can become awkward or uncomfortable, and the supine position should be avoided after the mid-second trimester. General prenatal guidelines suggest maintaining a moderate intensity, ensuring adequate hydration, and avoiding overheating during any exercise.
One of the first modifications for hip thrusts is to elevate the barbell using blocks or plates, which decreases the range of motion and creates space for the growing belly at the bottom of the movement. Adding extra padding to the bar can also increase comfort by reducing direct pressure on the upper thighs and lower abdomen. Switching the resistance from a heavy barbell to resistance bands or dumbbells allows for easier setup and removal, and also helps to reduce overall load.
If the flat back position becomes uncomfortable or causes any symptoms of lightheadedness, the exercise should be immediately modified or replaced. Alternatives that work the same muscle groups without requiring a supine position include standing cable kickbacks, elevated glute bridges, or a shift to a bodyweight glute bridge on the floor. Adjusting the training to avoid any movement that causes pain or coning in the abdomen is important as the physical demands of pregnancy evolve.