From the Guidelines
Embryo implantation typically does not cause elevated body temperature. After an embryo implants in the uterine lining, which occurs about 6-12 days after ovulation, most women do not experience a noticeable increase in their basal body temperature specifically due to implantation. While some women might report feeling warmer during early pregnancy, this is generally attributed to the hormonal changes that occur after implantation has already taken place, particularly the continued production of progesterone 1. Progesterone naturally elevates body temperature during the luteal phase of the menstrual cycle and continues to be produced in increasing amounts after successful implantation. A sustained elevated temperature beyond the typical 14-day luteal phase can be an early sign of pregnancy, but the implantation process itself is not directly responsible for causing fever or significant temperature elevation. If you experience an actual fever (temperature above 100.4°F or 38°C) around the time of expected implantation, it's more likely due to an unrelated illness rather than the implantation process. Key points to consider include:
- The role of progesterone in elevating basal body temperature during the luteal phase and after implantation
- The distinction between feeling warmer and having a significant temperature elevation due to implantation
- The importance of monitoring for fever as a potential sign of unrelated illness rather than implantation itself Given the most recent evidence, the recommendation is to monitor body temperature changes in the context of overall health and pregnancy symptoms, rather than attributing temperature changes directly to embryo implantation 1.
From the Research
Embryo Implantation and Temperature
- The relationship between embryo implantation and temperature is complex, with various factors influencing the outcome 2, 3, 4.
- Elevated temperature can reduce developmental competence of the preimplantation embryo, and the embryo's sensitivity to heat shock varies depending on its genotype, stage of development, and exposure to regulatory molecules 2.
- Research suggests that maternal core body temperature increases of ∼2°C above normal for extended periods can result in developmental abnormalities in animal models 3, 4.
Effects of Heat on Embryos and Foetuses
- Hyperthermia during pregnancy can cause embryonic death, abortion, growth retardation, and developmental defects 3, 4.
- The development of the central nervous system is especially susceptible to elevated maternal temperatures, with a 2.5°C elevation for 1 h during early neural tube closure resulting in an increased incidence of cranio-facial defects 4.
- Thresholds and dose-response relationships vary between species and even between different strains of the same species, making it challenging to extrapolate data to humans 3, 4.
Embryo Implantation in the Laboratory
- The embryo implantation process is crucial for the correct establishment and progress of pregnancy, but it is still elusive to experimentation due to its inaccessibility 5.
- In vitro models have been proposed to recreate different stages of the implantation process, allowing for rapid high-throughput interrogation of embryos and cells, and efficient screening of molecules that control embryo implantation and endometrial receptivity 5.
- These models have contributed to the study of human reproduction by discovering molecules that control implantation, including hormones, signalling molecules, transcription factors, and cytokines 5.