Floating Babies and Zero-Gravity Birth: What Space Pregnancy Might Actually Involve

As plans for missions to Mars accelerate, so do questions about how the human body might cope. A return trip to the red planet would give more than enough time for someone to become pregnant and even give birth. But could a pregnancy be conceived and carried safely in space? And what would happen to a baby born far from Earth?

Most of us rarely consider the risks we survived before birth. For instance, about two thirds of human embryos do not live long enough to be born, with most losses happening in the first few weeks after fertilization; often before a person even knows they’re pregnant. These early, unnoticed losses usually happen when an embryo either fails to develop properly or to implant successfully in the wall of the womb.

Pregnancy can be understood as a chain of biological milestones. Each one must happen in the right order and each has a certain chance of success. On Earth, these odds can be estimated using clinical research and biological models. My latest research explores how these same stages might be affected by the extreme conditions of interplanetary space.

Microgravity, the near-weightlessness experienced during spaceflight, would make conception more physically awkward but probably wouldn’t interfere much with staying pregnant once the embryo has implanted.

However, giving birth, and looking after a newborn, would be far more difficult in zero gravity. After all, in space, nothing stays still. Fluids float. So do people. That makes delivering a baby and caring for one a much messier and more complicated process than on Earth, where gravity helps with everything from positioning to feeding.

At the same time, the developing fetus already grows in something like microgravity. It floats in neutrally buoyant amniotic fluid inside the womb, cushioned and suspended. In fact, astronauts train for spacewalks in water tanks designed to mimic weightlessness. In that sense, the womb is already a microgravity simulator.

But gravity is only part of the picture.

Radiation

Outside Earth’s protective layers, there’s a more dangerous threat: cosmic rays. These are high-energy particles—“stripped-down” or “bare” atomic nuclei—that race through space at nearly the speed of light. They’re atoms that have lost all their electrons, leaving just the dense core of protons and neutrons. When these bare nuclei collide with the human body, they can cause serious cellular damage.

Here on Earth, we’re protected from most cosmic radiation by the planet’s thick atmosphere and, depending on the time of day, tens of thousands to millions of miles of coverage from the Earth’s magnetic field. In space, that shielding disappears.

When a cosmic ray passes through the human body, it may strike an atom, strip its electrons, and smash into its nucleus, knocking out protons and neutrons and leaving behind a different element or isotope. This can cause extremely localized damage—meaning that individual cells, or parts of cells, are destroyed while the rest of the body might remain unaffected. Sometimes the ray passes right through without hitting anything. But if it hits DNA, it can cause mutations that increase the risk of cancer.

Even when cells survive, radiation can trigger inflammatory responses. That means the immune system overreacts, releasing chemicals that can damage healthy tissue and disrupt organ function.

In the first few weeks of pregnancy, embryonic cells are rapidly dividing, moving, and forming early tissues and structures. For development to continue, the embryo must stay viable throughout this delicate process. The first month after fertilization is the most vulnerable time.