Heatwaves pose significant health risks during pregnancy due to physiological changes that impair the body's ability to regulate temperature. With growing interest in the effects of heat on pregnancy, numerous studies have been published. However, the expanding evidence base remains fragmented, making it difficult to identify major patterns and gaps. This study combined bibliometric analysis and systematic review to map the existing literature and summarise key findings. A total of 259 articles published between 2000 and 2024 were retrieved from the Web of Science Core Collection. Most studies were conducted in high-income countries. Keyword analysis identified four major themes: preterm birth, methodological approaches, co-exposure to heat and air pollution, and physiological or mechanistic pathways. Most studies used cohort designs, and the distributed lag non-linear model, in combination with other methods, was the most common analytic approach. Preterm birth was the most frequently studied outcome, with strong evidence linking both acute and chronic heat exposure to increased risk. Several studies examined co-exposure to heat and air pollutants (e.g., PM₂.₅, PM₁₀) in relation to various pregnancy outcomes, reporting synergistic effects, such as up to 48% of preterm birth risk attributed to combined exposure. Antagonistic effects were also observed, such as between ozone and heat on pregnancy loss. Our review also identified pathways linking heat exposure to adverse outcomes. Maternal hypertension, placental weight, and fetal heart rate changes were reported as mediators, with effects ranging from 3.7% to over 50%. Other pathways included reduced uterine artery pulsatility index and impaired placental function. Some studies reported outcomes indicative of physiological stress and strain, such as increased heart rate, core temperature, white blood cell counts, and changes in newborn respiratory function. This review highlights the scarcity of studies from developing countries, the narrow focus on outcomes, methodological inconsistencies, and uncertainty surrounding the underlying mechanisms