The rapid spread of the Zika virus across Latin America, and its suspected link to an outbreak of birth defects, has prompted governments to do something without much precedent in human history: urge people to hold off on having kids. Facing what the World Health Organization has now called an international emergency, El Salvador has asked women to avoid getting pregnant until 2018, while countries such as Brazil and Colombia have suggested waiting several months, or indefinitely. Imagine you are trying to get pregnant, or already are, and you hear that message from your government. Would you take it seriously? And if you did, and all your peers did, what would that actually look like five, or 25, years out? Classes with no or hardly any students? Baby stores forced out of business? A depleted younger generation unable to support older ones?

What, in other words, are the social and economic consequences of a gap like that in a country’s or region’s population?

“It’s difficult to define what the effect could be because you don’t know how this epidemic will evolve,” said Jose Miguel Guzman, a former demographer at the United Nations who’s now with the consulting firm ICF International. He noted that there are 10 to 11 million births in Latin America per year, which means the population would drop by that number if, theoretically, all births were postponed for a year. “This is not a high percentage,” he told me. “Take into account that the population for Latin America is about 634-635 million.” But such a decline could cause the total population in the region, where birth rates have been falling for decades, to grow more slowly or contract sooner than expected.

The key variable to watch is how long the Zika outbreak persists. Populations have a way of boomeranging back when temporarily depressed by a war, epidemic, economic disaster, or some other shock to the system, Guzman said. If the outbreak lasts one or two years, it may produce an enduring “hole in the age structure.” But couples in Latin America, who typically have two children, would likely aim for the same family size they’d anticipated before the health crisis, perhaps compensating for lost time by speeding up their timeline for having kids. A 28-year-old woman who was hoping to have her first child at 30 and her second at 34 might, say, give birth at 32 and 34 instead.

“One year in a school you would have much less kids … but then in two years, they would have double [the number] of kids,” Guzman hypothesized. The socioeconomic repercussions would probably be minimal: Smaller grades for a couple years could mean fewer students per classroom and thus, potentially, better education for those students, but these dynamics wouldn’t have a major impact on educational systems and the labor market.

If the Zika epidemic lasts five years or more, however, the calculus could change. In that (very hypothetical) scenario, a significant portion of the women who postponed getting pregnant during the health crisis will be over the age of 35, when pregnancies carry a higher risk, and some of these women “will not have the possibility to have more kids.” That drop in the birth rate might not be canceled out by a subsequent rise, leading to a substantially smaller generation than otherwise would have emerged.

Such a shift in the age structure could present problems in Latin America, where the informal economy is massive and people tend to not save much money for the future. As a result, the elderly often depend more on material support from their kids and grandkids than on inadequate pension and social-security systems. Countries in the region, Guzman explained, appear to be growing old before they grow rich—a challenge that could be exacerbated by a prolonged struggle to contain the Zika outbreak.

Some public-health experts have questioned the wisdom of the recent government recommendations to avoid getting pregnant, and the advisories have proven politically explosive in largely Catholic countries with some of the strictest abortion laws in the world. (How do you tell Salvadoran women to not give birth for the sake of public health, while continuing to criminalize abortion under all circumstances?)

But officials appear to be grasping for solutions. Zika is slippery. There’s no vaccine or treatment for the mosquito-borne virus, which is suspected of causing a surge in Brazil of babies born with microcephaly, or an abnormally small head and brain damage. The precise link between the virus and birth disorders remains far from clear. Eighty percent of Zika patients don’t show symptoms. Combatting the virus involves pretty mundane and marginally effective things like spraying pesticides, covering your skin, using mosquito repellant, and dumping standing water where mosquitos can breed (and not-so-mundane things, such as genetically modifying mosquitos to kill off other mosquitos).

Guzman, for his part, isn’t so sure that the Zika virus, and the dire government warnings about it, will radically reduce birth rates. In Latin America, he noted, most births are unplanned. A 2014 study by the Guttmacher Institute found that 56 percent of pregnancies in Latin America and the Caribbean are unintended—a rate that is declining, but still the highest of any region in the world.

For that reason, it’s not enough for governments to simply encourage women to put off pregnancy, as if fertility were solely discretionary: “Those women, those couples, have to have the possibility to do so. And for that they need ... quick and good access to high-quality contraceptives and modern methods. And this is something that’s still missing in Latin America.”

Access is particularly difficult for the poorest segments of the population, and especially low-income, adolescent women, in a region with the greatest economic inequality on the planet. That inequality manifests itself in many ways, among them limited opportunities for the poor to receive good education, including sex education, which Church officials sometimes restrict or distort as well. (Still, in Latin America, 67 percent of women of reproductive age who are married or in a union are using some modern method of contraception; in the developing world as a whole, the figure is 56 percent.) High rates of rape in the region also contribute to the prevalence of unplanned pregnancies.

Guzman pointed out that other mosquito-borne diseases like malaria disproportionately affect the poor. “If we think that in the poorest group of the population, the incidence of the Zika virus will be higher, and also the possibility for those women to really not become pregnant is lower, that is the worst combination—the combination of inequality, [lack of] access to family planning, and also the characteristic of the virus that will be affecting more people who are poor,” he said. “Dealing, in a condition of poverty, with kids [with microcephaly] that are not able to be active or to be productive—that will really have an impact in terms of the capacity of families to transform their lives and leave the cycle of poverty.”

So far, Guzman hasn’t seen Latin American governments make a serious commitment to widening access to family-planning resources as part of their emergency Zika response. Calls to defer pregnancy are reductive unless they’re accompanied by an emphasis on women’s rights and needs, he argued. Without that emphasis, they’re also unlikely to be widely heeded.