45 CFR 46 Subpart B (Additional Protections for Pregnant Women, Human Fetuses, and Neonates)

45 CFR 46 Subpart B (“Additional Protections for Pregnant Women, Human Fetuses and Neonates Involved in Research,” §§46.201-46.207) is the Common Rule section that governs federally conducted or federally funded research in which the subjects are pregnant women, human fetuses, or neonates. Like Subpart C (prisoners) and Subpart D (children), it sits on top of the general Common Rule — an IRB must apply Subpart A’s ordinary approval criteria at §46.111 first, then layer Subpart B’s population-specific risk/benefit conditions and consent requirements on top wherever a subject falls into one of its defined categories.

Definitions Under §46.202

Subpart B’s applicability turns on precise regulatory definitions, not everyday usage of the terms:

• Pregnancy is defined as the period of time from implantation until delivery; a woman is presumed pregnant if she exhibits signs such as a missed menstrual period, until the presumption is ended by a negative pregnancy test, delivery, or other reliable determination.
• Fetus means the product of conception from implantation until delivery.
• Neonate means a newborn.
• Viable, as applied to a neonate, means being able, after delivery, to survive (given the benefit of available medical therapy) to the point of independently maintaining heartbeat and respiration.
• Nonviable neonate means a neonate after delivery that, although living, is not viable.

These definitions are load-bearing: whether a protocol is reviewed under §46.204, §46.205, or §46.206 depends on which of these categories the actual subject falls into at the time of the research, not on the study’s general subject matter.

Duties of the IRB (§46.203)

§46.203 requires the IRB, in addition to all other Common Rule responsibilities, to determine that the research satisfies the specific conditions of whichever of §§46.204-46.207 applies before approving it — Subpart B review is additive to, not a substitute for, the general §46.111 risk-minimization and informed-consent criteria.

Research Involving Pregnant Women or Fetuses (§46.204)

§46.204 permits research involving pregnant women or fetuses only where the IRB finds, among other conditions, that: appropriate studies on animals and non-pregnant individuals have been completed; the risk to the fetus is caused solely by interventions or procedures that hold out the prospect of direct benefit to the pregnant woman or fetus, or, if there is no such prospect, the risk to the fetus is minimized and is not greater than minimal; no inducements will be offered to terminate a pregnancy; individuals engaged in the research will have no part in determining the viability of a neonate or in decisions about the timing, method, or procedures used to terminate a pregnancy; and, where the research holds out the prospect of direct benefit to the fetus, the consent of the pregnant woman and the father is obtained, except where the father’s identity or whereabouts cannot reasonably be ascertained, he is not reasonably available, or the pregnancy resulted from rape or incest.

Research Involving Neonates (§46.205)

§46.205 splits neonatal research into two consent-eligible pathways depending on viability status, both requiring the general conditions at §46.205(a) (appropriate preclinical and clinical studies completed; individuals involved in the research have no part in determining the neonate’s viability):

• Neonates of uncertain viability may be involved if, additionally, the IRB determines the research holds out a reasonable possibility of enhancing the neonate’s survival to the point of viability, and any risk is the least possible for achieving that objective, or the research holds out the prospect of enhancing that particular neonate’s survival, or (for research not held out to hold that prospect) the research will not add to the neonate’s risk and its purpose is developing important biomedical knowledge not obtainable by other means, with the additional §46.205(c) conditions on consent applying as appropriate.
• Nonviable neonates may be involved only where the IRB determines vital functions will not be artificially maintained, the research will not terminate heartbeat or respiration, there is no reasonable possibility the research will suppress or terminate them, and the purpose is developing important biomedical knowledge not obtainable by other means, plus the specific parental-consent conditions at §46.205(c).

Once a neonate has been determined viable, it is no longer covered by §46.205 and instead becomes subject to Subpart D (or Subpart A generally, if outside Subpart D’s scope) as a child subject.

Research Involving, After Delivery, the Placenta, the Dead Fetus, or Fetal Material (§46.206)

§46.206 covers research on material obtained after delivery — the placenta, dead fetus, or fetal material — requiring that such research be conducted in compliance with any applicable federal, state, or local laws regarding the procurement, use, or disposal of such material, and that identifiable information not be recorded or used for a purpose the individual providing biospecimens has not consented to, in accordance with subpart A of this part.

Research Not Otherwise Approvable (§46.207)

§46.207 is a narrow escape valve, structured the same way as the parallel Subpart D provision at §46.407: research that does not satisfy §§46.204-46.206 may still be conducted or funded only if the HHS Secretary, after consulting a panel of experts and providing opportunity for public review and comment, determines that it presents a reasonable opportunity to further the understanding, prevention, or alleviation of a serious problem affecting the health or welfare of pregnant women, fetuses, or neonates, and will be conducted in accordance with sound ethical principles. As with §46.407, this pathway is rarely invoked precisely because it requires Secretarial-level public review rather than IRB-level approval alone.

Relationship to Subpart C and Subpart D

Subparts B, C, and D form a sibling family of Common Rule population-specific protections: Subpart B covers pregnant women, fetuses, and neonates; Subpart C covers prisoners; and Subpart D covers children. A single study can trigger more than one subpart — for example, a trial enrolling incarcerated pregnant participants would need to satisfy both Subpart B’s and Subpart C’s conditions. HHS finalized a rule (Federal Register document 2024-24399), effective October 24, 2024, that amended Subparts B, C, and D for technical and conforming alignment with the 2018-revised Common Rule, updating cross-references without changing which populations each subpart covers or the underlying protections described above.

Frequently Asked Questions

Does Subpart B apply only to federally funded research?

By its own terms, Subpart B binds HHS-conducted or HHS-funded research. As with Subpart D, institutions holding a Federalwide Assurance (FWA) with OHRP commonly extend Common Rule protections, including Subpart B, to all human-subjects research they conduct regardless of funding source, and several non-HHS federal agencies have separately adopted the Common Rule for their own funded research.

Does the father’s consent requirement under §46.204 ever apply outside pregnancy research?

No — it is specific to §46.204 research that holds out the prospect of direct benefit to the fetus, and even then it does not apply where the father’s identity or whereabouts cannot reasonably be ascertained, he is not reasonably available, or the pregnancy resulted from rape or incest.

What happens once a neonate of uncertain viability becomes clearly viable?

§46.205 governs only while viability is uncertain or the neonate is nonviable. Once the neonate is determined viable, further research involving that child is governed by Subpart D’s risk-category and parental-permission/assent structure rather than §46.205.

See also: Vulnerable Populations in Research, which situates Subpart B alongside Subparts C and D and the general §46.111(b) IRB safeguard criterion; 45 CFR 46 Subpart D (Additional Protections for Children in Research), the sibling subpart for pediatric subjects; Common Rule (45 CFR 46), the umbrella regulation; and OHRP (Office for Human Research Protections), the HHS office that administers and interprets the Common Rule including Subpart B.