Women of childbearing age in the developing world, especially in most countries in Africa, struggle to space their children and prevent unwanted pregnancies. Modern contraceptives are perceived to have side effects such as hormonal imbalance, increased risk of cancer, thromboembolism, weight gain, heavy menstrual bleeding, and genital infections [9, 18]. The use of plants for contraceptive purposes is an age-old practice that is deeply embedded in the cultural and medicinal heritage of several communities across Nigeria. However, with the increasing influence of modern medicine and the potential decline in the transmission of this knowledge to younger generations, there is a pressing need to preserve this information [56].

The participants in this study were predominantly married female herb sellers who were 31–50 years of age, in contrast to the number of male participants. This finding indicates that women, particularly those in middle to older age groups, are the primary custodians of traditional contraceptive knowledge. Female herb sellers, who frequently interact with other women, are likely to be well informed about contraceptive herbs, both for personal and professional use [45]. Additionally, in many societies, particularly in rural areas, women play a crucial role in local health practices. This disparity can be understood through sociocultural roles, knowledge dynamics, and economic factors specific to gendered practices in the realm of reproductive health [4].

The educational background varied across the four states, with a significant proportion having secondary and tertiary education. The varied educational backgrounds of the participants highlight the mix of traditional and formal knowledge systems in the practice of ethnobotany. Their literacy and education also enable them to understand the basics of contraceptive use and efficacy, aligning their knowledge with community needs in a practical manner [42].

These sociodemographics indicate that traditional contraceptive knowledge is held by experienced, educated, and married individuals. This analysis is crucial for understanding the dynamics of knowledge preservation and the role of different groups in maintaining traditional contraceptive practices. There have also been reports of a positive association between respondent age and plant knowledge acquisition [51].

Informant Consensus Factor (ICF) describes informants’ consensus on the medicinal plant consumption and evaluates variability in mode of utilization for contraception [22, 53]. The ICF values calculated for Kwara, Lagos, Oyo, and Osun study areas were 0.5, 0.6, 0.3 and 0.8 respectively, with an overall ICF value of 0.7 across the four areas. A similar informant consensus factor (0.6) was reported in an ethnobotanical study on medicinal plants species used for contraception and reproductive health care in four regions in Uganda [11, 33]. The results obtained from this study demonstrated that the herb sellers and herbal practitioners, who participated in the study tend to agree with each other in terms of the plant species used as contraceptives, which is an indication of quality control of administration of herbal remedies.

The RFC index authenticates the citation frequency of a medicinal plant used for treating various ailments. It also represents the relative importance of plant species and it is dependent on the number of informants that report their usage [53, 54]. In this study, RFC values ranged from 2 to 27% in Kwara, 2.5% to 30% in Lagos, 8% to 58% in Oyo, and 6% to 44% in Osun. Across the four study areas, the highest RFC was found for Mucuna pruriens (0.31), Carica papaya (0.21) and Jatropha gossypiifolia (0.14). This demonstrates that the vast majority of respondents in the study areas agreed that these species were the most often prescribed medicinal plants for contraception. Mucuna pruriens has been traditionally used for various medicinal purposes, including its potential role as a herbal contraceptive. However, studies have reported that M. pruriens may enhance fertility instead of acting as a contraceptive [46]. Mucuna pruriens seeds have been reported to improve male sexual function as well as enhance uterine and ovarian functions in animal models [10, 47, 50]. Therefore, while traditional practices may have associated M. pruriens with contraceptive properties, current scientific evidence suggests it may actually enhance fertility. In traditional medicine, different parts of C. papaya such as leaves, stem, roots and seeds are used in the management of various diseases. In search for male contraceptive agents, C. papaya seed extract has been widely studied for its antifertility properties [28,29,30,31,32]. The effects of C. papaya seeds on the male reproductive system have been well-documented, with concerns raised regarding the potential risks of seed ingestion during pregnancy. In female animals, the antifertility action of C. papaya seeds is primarily based on traditional knowledge, with conflicting reports regarding its precise mechanism in inducing infertility [25]. Different parts of J. gossypiifolia including its leaves, stems, roots, and seeds have been reported to exhibit several pharmacological activities, such as anti-inflammatory, analgesic, anti-microbial, anti-diabetic and contraceptive effects [23, 24, 44].

The most predominant plant families were Fabaceae, Euphorbiaceae, and Cariacaceae. The Fabaceae family was the most frequently cited, occurring 37 times. This high frequency of citation may be attributed to the wide variety of species within Fabaceae, also known as the legume family, which is known for its diverse secondary metabolites, including alkaloids, flavonoids, and glycosides. These compounds have been linked to antifertility effects, potentially explaining why Fabaceae species are favored in traditional contraceptive practices [2, 43]. The prominence of Fabaceae in such traditional uses has also been noted in studies across African regions, reinforcing its ethnobotanical importance [12].

In addition to Fabaceae, the Euphorbiaceae family ranked second with 28 occurences and the Caricaceae family ranked third with 23 occurrences in the survey. Euphorbiaceae is rich in diverse bioactive compounds, such as diterpenes and triterpenes, many of which have been researched for their pharmacological potential, including their antifungal and abortive properties [38, 39]. Plants in the Caricaceae family, particularly Carica papaya, are well documented in traditional medicine for their role in regulating fertility, with components such as papain believed to influence reproductive health [52]. The life forms of most of the plants cited as contraceptive medicinal plants in the four studied areas were trees, with the plant parts most commonly used being seeds, leaves, bark, fruits and rhizomes, which indicates a reliance on more substantial, possibly long-standing flora for contraceptive purposes. One prominent preparation method is herbal contraceptive powder, which is made by grinding the plant materials such as seeds or leaves into a fine powder. This powder is ingested with a medium such as pap food or water. This approach is likely to make the bioactive compounds more digestible and palatable, facilitating their intended contraceptive effects. Another method involves boiling the plant parts, after which the resulting decoction is consumed. Boiling may enhance the potency of the medicinal properties by extracting active constituents but may also render the remedy easier to ingest. In certain cases, plant materials are mixed with ash or boiled with other items, such as waist/wrist beads or rings, suggesting symbolic or ritualistic effects in addition to practical and pharmacological effects. The addition of ash may also serve as a preservative or additional binding agent, enhancing the effectiveness of the mixture [5].

Furthermore, some preparation techniques involve more prolonged processes, such as soaking plant materials alone or with rings or waist/wrist beads for several days. These extended soaking periods could serve to leach specific active compounds gradually, enhancing the potency or stability of the contraceptive. Methods involving boiling and/or drying, such as boiling rings with contraceptive herbs and allowing the rings to dry for three days, may carry cultural or symbolic significance, reflecting the belief that ritualistic handling can influence the efficacy of the contraceptive (Bablola et al. 2009). The use of contraceptive rings could have some consequences with periods and times of sexual intimacy, as emphasized by 5 out of the 41 participants in Kwara study area and 3 out of the 12 participants in Oyo study area. Further instructions/advice against the concurrent use of traditional and modern contraceptives were also given, which could stem from concerns over interactions that might reduce effectiveness or cause side effects. The oral route of administration (48.6%) was the most common route prescribed by respondents to female contraceptive seekers, aligning with the general preference for the ingestion of medicinal plants. This could indicate that the active compounds in these contraceptive plants are believed to work systemically. The use of incisions, though less common, suggests that some traditional practices might involve topical or localized applications, possibly in conjunction with spiritual or ritualistic practices [27]. Many of the participants (96.3%) reported no side effects from the use of these plants, which might have contributed to their continued use in traditional practices. The small percentage of reported side effects, particularly general body pain, could be due to individual sensitivities, dosage differences, or the preparation method [48]. Some of the excerpts quoted from the participants include “Do not use traditional contraceptives together with modern contraceptives”. Another traditional contraceptive provider was quoted to have affirmed that “the contraceptive ring will work as long as you wear it” and, importantly, about the need for a firm belief in effectiveness: “When you believe it will work without asking questions, it will work”. Based on these themes, quotes and excerpts, it can be inferred that traditional contraceptive providers generally believe that their products and services, if prepared accurately and instructions are well followed, effectively assist women in planning their birth.

A chi-square test was used to identify significant relationships between the form of the plant (such as seeds, leaves) and various participant attributes or conditions of contraceptive usage. A statistically significant association (p = 0.018) between plant form and participants’ level of education suggested that educational background may influence the choice of plant parts recommended as herbal contraceptives. A higher educational attainment may therefore influence preferences toward certain plant parts or preparation methods due to differences in perceived efficacy, safety, or cultural knowledge [2]. This finding aligns with studies indicating that education often impacts health behaviors, including contraceptive choices and methods [49].

Another statistically significant association (p = 0.001) between plant form and experience with herbal contraceptive patients suggests that individuals who have assisted others in contraceptive use may prefer to recommend specific plant parts due to their efficacy or perceived reliability. This association may indicate practitioner expertise, where experience influences the selection of plant forms most aligned with successful contraceptive outcomes [17].

In contrast, no statistically significant associations were found between plant part and participant status (p = 0.549), route of administration for males (p = 0.224), route of administration for females (p = 0.273), or side effects of the plant (p = 0.593). The lack of association between plant part and participant status—such as whether the participant was a practitioner, user, or general informant—indicates that plant form preference may be more culturally or community-based rather than role-specific within the population surveyed. Similarly, the absence of a significant relationship with the route of administration for both males and females implies that plant form selection is likely independent of the intended mode of delivery (e.g., oral, topical), with variations perhaps rooted in local cultural practices rather than biological gender considerations.

Finally, the nonsignificant results concerning the plant form and side effects of the plants suggest that side effects may not be directly tied to the plant itself but rather to the individual plant species or preparation methods used. This finding underscores the potential complexity of ethnobotanical contraceptive side effects, where variables such as dosage, individual tolerance, and preparation may play more influential roles [13].