Commentary: No Evidence to Show Fetal Pain in Second Trimester

Earlier this month, the US House of Representatives passed a bill that would ban abortions after 20 weeks fertilization with very few exceptions. [Editor's note: The bill defines 20 weeks as 20 weeks post-fertilization, equal to 22 weeks after the last menstrual period.] This bill will restrict access to care, will take treatment options away from patients, will mandate how healthcare professionals are supposed to approach second-trimester abortion care, and will represent another step backward—this time, at the Federal level—for women in America.

Even though this measure is not yet law—and hopefully will not become law—it is already planting seeds of confusion about fetal development during gestation, one of the most unfounded being the false existence of fetal pain in the second trimester. We have seen the havoc that state restrictions like this have created for women's access to care, all based on mischaracterization of science.

The name of the bill itself speaks volumes: the "Pain-Capable Unborn Child Protection Act." Clearly intended to create bias, this name is blatantly inaccurate and unscientific.

Quite simply, there is no evidence to suggest that fetuses are capable of feeling pain during the second trimester, especially at 20 weeks. This is not a matter that is subject to interpretation; rather, the explanation is tied intrinsically to the physiologic development of the fetus's brain and nervous system, which do not have the capacity to process, recognize, or feel pain during the second trimester.

The Science Is Clear

Medical decisions must be based on science, and the science is clear.

In 2005, a multidisciplinary review published in the Journal of the American Medical Association clearly and comprehensively addressed this issue. This landmark review incontrovertibly found no existence of fetal pain until much later in gestation.^[1] Importantly, no research since its publication has contradicted its findings.

The review found that the gestational brain developments that are necessary for pain simply don't occur until the third trimester. This is largely based on the creation and eventual connection of thalamocortical pathways. The authors wrote: "The capacity for conscious perception of pain can arise only after thalamocortical pathways begin to function, which may occur in the third trimester around 29 to 30 weeks' gestational age, based on the limited data available."

It is true that thalamocortical fibers begin to form between 23 and 30 weeks of gestation, but the authors emphasize that while "the presence of thalamocortical fibers is necessary for pain perception, their mere presence is insufficient—this pathway must also be functional." This happens at around 30 weeks.

ACOG's counterpart in the United Kingdom, the Royal College of Obstetricians and Gynaecologists (RCOG), reached a complementary conclusion in 2010: "In reviewing the neuroanatomical and physiological evidence in the fetus, it was apparent that connections from the periphery to the cortex are not intact before 24 weeks of gestation and, as most neuroscientists believe that the cortex is necessary for pain perception, it can be concluded that the fetus cannot experience pain in any sense prior to this gestation." Full development requires an additional 8-10 weeks, RCOG found.^[2]

Fetuses vs Premature Neonates

Reproductive-rights opponents point to premature neonates as evidence of pain in a fetus, but the RCOG analysis found good evidence that conditions within the womb distinguish fetal experience of sensation from those of premature infants of similar gestational age. As RCOG explains, "there is increasing evidence that the fetus never experiences a state of true wakefulness in utero and is kept, by the presence of its chemical environment, in a continuous sleep-like unconsciousness or sedation. This state can suppress higher cortical activation in the presence of intrusive external stimuli."^[2]

The JAMA analysis also suggested such a finding, reporting that electroencephalography patterns that represent wakefulness do not exist in fetuses until roughly 30 weeks.^[1]

What About Fetal Movement?

Opponents of reproductive rights argue that fetal movement supports their position. Of course fetuses move in utero. However, we are mistaken if we assign a meaning to fetal movement. Fetal movement can be reactive to certain stimuli, but that does not mean that there is a specific sensation of pain. Fetuses can't comprehend or interpret sensations in the way that a newborn infant can.

The authors of the JAMA review agree, writing: "Pain perception requires conscious recognition or awareness of a noxious stimulus. Neither withdrawal reflexes nor hormonal stress responses to invasive procedures prove the existence of fetal pain, because they can be elicited by nonpainful stimuli and occur without conscious cortical processing."

A Commitment to Patients

As physicians, we make a commitment to treat our patients based on science and best practices—not ideology. Women who are facing a second-trimester abortion are usually facing complex, often heart-wrenching situations, and they deserve empathetic care, not attacks and not mistruths. As an obstetrician-gynecologist, I have dedicated my career to the care and well-being of women at all points in their lives, and this includes during the painful time in which a woman may need to terminate a pregnancy.

At ACOG, we recognize that not every ob-gyn will choose to provide abortion care,^[3] but we do hope that our colleagues will not be a barrier to women getting the care that they need, when they need it.

No physician, regardless of specialty, should manipulate and mischaracterize evidence in order to stand in the way of proven science, of the practice of medicine, and of the lives of our patients.

Finally, no lawmaker should pursue nonscientific, unconstitutional legislation that obstructs the provision of good healthcare. Medical and legislative decisions should be based on science, not ideology.

[Editor's note: Click here to read a counter-commentary from the Christian Medical & Dental Associations.]

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