Maternal nutrition is crucial for health in pregnancy and across the generations. Experiencing food insecurity during pregnancy is a driver of inequalities in maternal diet with potential maternal and infant health consequences. This systematic review explored associations between food insecurity in pregnancy and maternal and infant health outcomes. Searches included 8 databases (MEDLINE, Embase, Scopus, Web of Science, PsychInfo, ASSIA, SSPC in ProQuest, and CINAHL), grey literature, forwards and backwards citation chaining, and contacting authors. Studies in high-income countries (HICs) reporting data on food insecurity in pregnancy and maternal or infant health, from January 1, 2008 to November 21, 2023 were included. Screening, data extraction, and quality assessment were carried out independently in duplicate. Random effects meta-analysis was performed when data were suitable for pooling, otherwise narrative synthesis was conducted. The protocol was registered on PROSPERO (CRD42022311669), reported with PRISMA checklist (S1 File). Searches identified 24,223 results and 25 studies (n = 93,871 women) were included: 23 from North America and 2 from Europe. Meta-analysis showed that food insecurity was associated with high stress level (OR 4.07, 95% CI [1.22, 13.55], I2 96.40%), mood disorder (OR 2.53, 95% CI [1.46, 4.39], I2 55.62%), gestational diabetes (OR 1.64, 95% CI [1.37, 1.95], I2 0.00%), but not cesarean delivery (OR 1.42, 95% CI [0.78, 2.60], I2 56.35%), birth weight (MD -58.26 g, 95% CI [-128.02, 11.50], I2 38.41%), small-for-gestational-age (OR 1.20, 95%, CI [0.88, 1.63], I2 44.66%), large-for-gestational-age (OR 0.88, 95% CI [0.70, 1.12] I2 11.93%), preterm delivery (OR 1.18, 95% CI [0.98, 1.42], I2 0.00%), or neonatal intensive care (OR 2.01, 95% CI [0.85, 4.78], I2 70.48%). Narrative synthesis showed food insecurity was significantly associated with dental problems, depression, anxiety, and maternal serum concentration of perfluoro-octane sulfonate. There were no significant associations with other organohalogen chemicals, assisted delivery, postpartum haemorrhage, hospital admissions, length of stay, congenital anomalies, or neonatal morbidity. Mixed associations were reported for preeclampsia, hypertension, and community/resilience measures. Maternal food insecurity is associated with some adverse pregnancy outcomes, particularly mental health and gestational diabetes. Most included studies were conducted in North America, primarily the United States of America, highlighting a research gap across other contexts. Further research in other HICs is needed to understand these associations within varied contexts, such as those without embedded interventions in place, to help inform policy and care requirements.