During which stage of pregnancy is the risk of miscarriage highest?

The risk of miscarriage is highest during the first trimester of pregnancy. This stage encompasses the initial 13 weeks and is characterized by significant hormonal changes, critical embryonic development, and the establishment of early placental support. During this time, a variety of factors, including chromosomal abnormalities, maternal health conditions, lifestyle factors, and environmental influences, can contribute to the likelihood of miscarriage.

Most miscarriages occur due to chromosomal issues that prevent the embryo from developing properly, which are most common in the early stages of pregnancy. As the pregnancy progresses into the second and third trimesters, the risk of miscarriage substantially decreases. By the end of the first trimester, the embryo's major organs and systems are in place, and the body transitions into a more stable phase of pregnancy, thus reducing the likelihood of loss. Conception itself represents just the very initial phase of a potential pregnancy, not a stage where miscarriage risk can be defined in the same way as during the subsequent trimesters.