Across sub-Saharan Africa, one in four married women who don’t want to become pregnant still aren’t using any form of contraception. This puzzling gap between intentions and actions has persisted despite decades of efforts to make birth control more available and more affordable.
In recent research with Grant Miller (Stanford University) and Christine Valente (University of Bristol), we conducted a survey of women in Mozambique who said they didn’t want to get pregnant in the next two years (Miller et al, 2025). Our findings offer some unexpected insights into why birth control isn’t used to prevent pregnancy – and point to a surprisingly simple solution.
The mystery of unmet need for family planning
In development and demography research, the phenomenon of unused birth control is referred to as the unmet need for family planning. The numbers are staggering. Over 52 million unwanted pregnancies occur each year in low-income countries, contributing to about 70,000 maternal deaths from unsafe abortions.
What makes this particularly concerning and puzzling is that when women are asked directly why they don’t use contraception, fewer than 10% cite cost or lack of access as the main reason. So, if it’s not about money or availability, what’s really going on?
Beliefs about birth control
To answer this question, we surveyed 584 women in Mozambique who said they didn’t want to get pregnant in the next two years. Instead of just asking about their choices, we dug deeper into what these women actually believe about different contraceptive methods – their perceived risks, benefits, costs and side-effects.
Women were asked to report the likelihood of an event (such as a pregnancy or adverse effect) for a given method by placing beans on a ruler (see Figure 1). A score of 20 on the ruler would mean that the woman was absolutely certain that this outcome would happen, while a score of 0 would mean that she was absolutely certain that this would not happen.
Figure 1: System for measuring attitudes towards birth control
Source: Author’s methodology
The findings are eye-opening. While women have surprisingly accurate knowledge about some aspects of contraception (such as the effectiveness of condoms), they have significant misconceptions about others.
First, many women dramatically underestimate their risk of getting pregnant without birth control. About 40% of women think that their chances are lower than the actual risk. According to medical research, 85% of sexually active women who don’t use contraception will become pregnant within a year. But many women in the study think that their personal risk is much lower.
Second, women vastly overestimate how often hormonal methods fail. While methods such as injections and implants are actually highly effective (failing less than 1-6% of the time), the women in our study think that they fail 19-25% of the time – making them seem barely better than using nothing at all.
Testing what really matters
We used statistical techniques to seek to understand which factors actually influence women’s contraceptive choices. We then tested various scenarios to see what would have the biggest impact on increasing use of birth control.
As Figure 2 illustrates, one can imagine women choosing among no contraceptive method, a hormonal method and condoms. If a woman chooses the hormonal method instead of no method or condoms, she then picks among injection, pills or implant.
Figure 2: Research methodology visualisation
Source: Author’s methodology
The results of our analysis challenge conventional wisdom about what prevents women from using contraception.
Supply-side fixes have surprisingly little impact: even eliminating all costs, waiting times and supply problems would only increase contraceptive use by about one percentage point. This suggests that while simply making birth control cheaper and more available is important, it won’t solve the problem on its own.
Side-effects aren’t the main barrier either: completely eliminating all side-effects would increase use by less than half a percentage point. Indeed, some side-effects are actually seen as benefits: many women value the lighter or absent periods that come with some hormonal methods.
Male partners’ attitudes matter: if all partners were to approve of contraceptive use, it would increase uptake by 7.5 percentage points. If couples were to have aligned fertility goals, use would increase by 2.4 percentage points.
The biggest potential impact comes from correcting misperceptions about pregnancy risk. If women who underestimate their risk of pregnancy were to be given accurate information, contraceptive use could increase by 6.7 percentage points (among this group).
The information experiment
To test whether correcting beliefs would change behaviour, we conducted a simple experiment. We randomly selected some women and told them: ‘studies show that, on average, out of every 20 sexually active women of reproductive age who do not use any contraceptive method, 17 will get pregnant within the next 12 months’.
The results are clear: women change their beliefs almost immediately, bringing them much closer to the actual medical statistics. More importantly, their intentions to use contraception increase significantly, rising by 4.4 percentage points among women who initially underestimate their pregnancy risk.
Among women who aren’t currently using any contraception, the effect is even larger: intentions to use birth control increase by 8.2 percentage points after receiving the information.
Why this matters
These findings suggest that a significant portion of the global unmet need for family planning isn’t really about access, affordability or side-effects. Instead, it’s about information – specifically, accurate information about the risk of pregnancy without contraception.
This is good news for policy-makers and public health practitioners because information programmes are relatively cheap and easy to implement compared with major infrastructure investments or new medical technologies.
Our research also highlights the crucial role that male partners play in contraceptive decisions. Women’s perceptions of their partners’ approval is the strongest predictor of contraceptive choice in our study. This suggests that family planning programmes need to engage men as much as women.
Looking forward
While our study was conducted in Mozambique, the findings are likely to apply to other countries where there are knowledge gaps about contraception. The key insight is that people make decisions based on what they believe to be true, not necessarily what is shown by empirical evidence.
For the millions of women worldwide who want to avoid pregnancy but aren’t using contraception, the solution might be simpler than we thought: giving them accurate information about their actual risk of pregnancy delivered in a way that they trust and understand.
But information alone isn’t a silver bullet. Our research shows that partner attitudes, cultural factors and access all matter too. Even so, correcting basic misperceptions about pregnancy risk could be a powerful, low-cost tool for reducing unwanted pregnancies and improving women’s reproductive autonomy around the world.
The next challenge is figuring out how to deliver this information effectively and at scale – a much more manageable problem to have compared with trying to build entirely new healthcare systems from scratch.
