While the CIOMS Guidelines support inclusion of pregnant women in research, existing laws in Latin America tend to be more restrictive . The laws often permit only a subset of studies that would be considered ethical under the CIOMS Guidelines. It is not uncommon for pregnant women  or even women of childbearing age  to be referred to as a vulnerable population in regulatory frameworks of Latin American countries. Pregnant women are commonly permitted to participate in research for conditions that solely affect pregnant women or their fetuses—meaning that pregnancy is a requirement for inclusion in the study . Several countries require that the father of the fetus also give consent to a pregnant woman’s participation in research unless circumstances make it impossible to do so [10,11,12]. For women of childbearing potential who are enrolled in research, the use of at least one contraception method is often required to ensure that they do not become pregnant during the study . Women who become pregnant during a study are, as a rule, automatically removed from the study [11, 13, 14].
With few exceptions [10, 12], relevant laws in Latin America do not distinguish between studies that do or do not offer potential benefit for the pregnant woman or the fetus. As a result, the standard provisions for studies with no potential individual benefit are often applied to all cases of research during pregnancy. Definitions of minimal risk  and distinctions between levels of risk for research with pregnant women  are often absent, thus leading to a precautionary position that treats all levels of risk as equally unacceptable, which ultimately results in a categorical exclusion of pregnant women from all research that involves any risk—no matter how small—to either the pregnant woman or the fetus. While ethics review committees are tasked with reviewing and approving studies prior to their initiation, the regulatory frameworks often do not leave much leeway to the committees’ assessment on the basis of the specific characteristics of individual protocols because a share of research involving pregnant women is often already forbidden or restricted by the regulations. In a nutshell, a legitimate concern with the protection of pregnant women and their fetuses in research has prompted regulatory action and implementation that often forbids in all cases what might be unethical in some cases.
The United States permits pregnant women’s participation in research under conditions specified in federal regulations, known colloquially as the “Common Rule” and “Subpart B” [15, 16]. The Common Rule requires that research be reviewed and approved by a local ethics committee, known as an institutional review board (IRB), which is subject to national oversight. The Common Rule generally applies to research institutions and researchers that receive US federal funding or otherwise agree to abide by those directives. Subpart B specifies additional ethics requirements for research involving pregnant women, fetuses, and neonates, and is more limited in application than the Common Rule because not all government agencies have adopted Subpart B . Both regulations may apply to international institutions and individuals (e.g., when they receive US government funding or otherwise agree to comply with the regulations). Pharmaceutical products (drugs, devices, and biologics) are subject to additional regulations promulgated by the Food and Drug Administration (FDA) [18,19,20]. The FDA does not have regulations specific to research with pregnant women, but has promulgated a number of guidelines on the topic .
Subpart B begins with a presumption that pregnant women, where pregnancy is defined as the period of time from implantation until delivery, may be included in research, provided certain conditions are met. According to Subpart B, the permissibility of research with pregnant women hinges on a judgment of the potential benefits and risks of the research. Approval of proposed research carrying no “prospect of direct benefit” to the woman or fetus requires that the risk to the fetus be judged “not greater than minimal” . Fetal risk that exceeds that standard is permissible only when the proposed research offers a prospect of direct benefit to the pregnant woman, the fetus, or both. Notably, if the proposed research does not fit within either of those two parameters, Subpart B offers an additional mechanism at the national level for approval by the Secretary of Health and Human Services. To our knowledge, that process has never been used.
Lastly, consent of the woman is required in all cases. The consent of the father, however, is not mandatory unless the research has a prospect of direct benefit solely to the fetus (i.e., no such benefit to the pregnant woman herself). Exceptions to the paternal consent requirement are permissible when the father is unavailable, incompetent, temporarily incapacitated, or when the pregnancy resulted from incest or rape.
Although pregnant women are currently classified as “vulnerable” in the Common Rule, along with children, prisoners, and people with disabilities , a forthcoming revision removes that classification .