Many in the medical community believe there’s clear evidence that a fetus – a developing baby in the womb – can’t feel physical pain until after the 24th week (6th month) of pregnancy. But other scientists say it’s possible for a fetus to feel pain as early as 12 weeks (3 months) into its development.
Much of the disagreement centers on whether certain parts of the brain and nervous system must be fully developed before a fetus can feel pain. There’s also uncertainty over the definition of pain itself. Can a fetus that doesn’t have consciousness (awareness) yet really experience it?
There are no easy answers. But the debate has implications for decisions around abortion and fetal surgery (operations done in the womb to treat birth defects and other medical conditions).
What Does the Research Say About Fetal Pain?
Research into fetal pain is complicated. Researchers can’t know for certain if a fetus feels pain. They must rely on what they know about fetal development and consider the fetus’ physical and hormonal responses.
Until the late 1980s, the medical community believed that even newborns couldn’t feel pain since their brains aren’t fully developed. But scientists began to consider the concept of nociception – the body’s ability to perceive harm. It’s not the same as pain because it doesn’t require awareness. Scientists say nociception itself can cause a stress response that could affect how a fetus’s brain or stress response system develops.
Today, the position of many major medical organizations, including the American College of Obstetricians and Gynecologists (ACOG), the Society for Maternal-Fetal Medicine (SMFM), and the Royal College of Obstetricians and Gynaecologists (RCOG), is that a fetus isn’t capable of feeling pain until at least 24-25 weeks.
These groups say research shows that:
- The cortex, the outer layer of the brain thought to be largely responsible for consciousness, and the thalamus, which relays sensory information (like pain) to the cortex, develop only after 24 weeks.
- Just because a fetus has other brain structures that process pain doesn’t mean the connections that can cause it to feel pain are working yet.
- The nerve connections that allow a fetus to tell the difference between a harmless touch and a painful one don't develop until late in the third trimester.
- When a fetus under 28 weeks seems to respond to “noxious stimuli” (actions an adult would perceive as unpleasant), it’s a reflex or hormonal reaction.
- While doctors may use pain-relieving drugs during fetal surgery, it’s mostly to keep the fetus from moving or prevent long-term damage from stress.
There’s some evidence, though, that a fetus could feel pain earlier than 24 weeks – perhaps as early as the first trimester. According to this research:
- It’s not clear whether a fetus needs a cortex to feel pain.
- Pain receptors start developing in the body by 7 weeks and are linked to the brain by 12-15 weeks.
- There are pathways for pain in a brain structure called the cortical subplate as early as 12 weeks and in the thalamus as early as 7 weeks.
- The thalamus and the brain stem, both of which start developing during the first trimester, are involved in consciousness.
- A fetus’s brain chemicals don’t cause it to be asleep or unconscious most of the time, as some scientists say.
The debate over fetal pain is further clouded by the fact that medical advances have made it possible for premature infants to survive at earlier and earlier ages. Babies born at 22-23 weeks now have a chance of survival. And doctors today tend to agree that newborns – even premature ones – can feel pain.
How Does This Affect the Abortion Debate?
Fetal pain is often cited as a reason to restrict abortion. It’s one reason why most states limit legal abortion to certain stages of pregnancy. As of spring 2023:
- Four states banned abortions at various points between 6 and 20 weeks.
- Nine states banned them at 22 weeks.
- Four states at 24 weeks.
- Three at viability (when the fetus is likely to survive if delivered).
- One state in the third trimester (25 weeks).
- Thirteen states prohibited abortions entirely.
But even before these laws took effect, most abortions in the U.S. were performed early in pregnancy. According to 2020 figures from the CDC:
- More than 93% of abortions were done at or before 13 weeks.
- 5.5% were done between 14 and 20 weeks.
- Less than 1% were performed after 21 weeks.
Though scientists don’t have all the answers on fetal pain, some say it’s reasonable to consider giving fetuses pain-relieving drugs during late abortions.
What Do We Know About Pain During Fetal Surgery?
For most fetal surgeries, doctors give the parent anesthesia that crosses the placenta and affects the fetus as well. But some scientists say this doesn’t guarantee the fetus gets enough of the drug to prevent potential pain or stress from the operation.
After the second trimester, doctors generally also give the fetus pain-relieving medicine, such as an opioid, along with a drug that stops it from moving around. This prevents the stress reaction that the American Academy of Pediatrics says can have harmful effects on their development.
Doctors have begun providing pain relief directly to fetuses during surgery at earlier and earlier stages of development, some experts say. The American Society of Anesthesiologists and the North American Fetal Therapy Network recommend that fetuses get pain-relieving drugs for all invasive surgeries.
This is considered safe for both parent and fetus. Side effects from giving a fetus anesthesia directly during surgery are rare.