The national birth registry shows a substantial baby bust in 2021 – the first full year plus nine months into the COVID-19 pandemic. The fertility of native Costa Rican women dropped by 13%. This decrease seems to be a continuation of preexisting fertility decline rather than an outcome of the pandemic. In contrast, a brief plunge in conceptions during the first full month of the pandemic (April 2020) decreased the fertility rate in January 2021 by as much as 24% for some groups. This plunge was a response to the hardships caused by pandemic mitigation measures as well as uncertainties and fears concerning the novel disease rather than to the physiological harm of the disease itself. The decrease in births among immigrant women (who contribute one-fifth of the birth rate) during the pandemic was 78% larger than among native women, driven mostly by pandemic-induced migration decisions. The data hint at a pandemic baby boom in low-SES communities and, especially, in families with several children.