Hegar’s sign is an early physical indicator associated with pregnancy, involving a specific change in the consistency of a part of the uterus. It was historically used by healthcare professionals as a probable indicator of pregnancy.
Understanding Hegar’s Sign
Hegar’s sign is a specific physical change in the uterus that healthcare professionals can detect during an early pregnancy examination. It involves the noticeable softening and increased compressibility of the uterine isthmus, which is the narrow, lower segment of the uterus located just above the cervix. Normally, this area feels firm to the touch. When Hegar’s sign is present, this segment becomes remarkably soft and pliable, almost feeling empty.
A healthcare professional assesses this change during a bimanual pelvic examination. In this procedure, one or two fingers are gently inserted into the vagina to palpate the lower uterine segment, while the other hand applies gentle pressure on the lower abdomen. The unique sensation is that the abdominal and vaginal fingers can seemingly come very close together, as if the uterine tissue between them is exceptionally thin and compressible. This distinct pliability creates an impression that the firm cervix and the main body of the uterus are separated by a very soft, almost non-existent, middle section. It is classified as a probable sign of pregnancy, though it does not provide absolute confirmation, as similar changes could theoretically arise from other conditions.
When and Why it Occurs
Hegar’s sign becomes detectable in early pregnancy, appearing between 4 to 6 weeks and persisting until about 12 weeks of gestation. It is most apparent during the 6th to 8th week. This physical change results from physiological adaptations within the uterus. The softening is due to elevated levels of pregnancy hormones, notably estrogen and progesterone.
These hormones trigger increased vascularity, leading to a greater blood supply to the uterine tissues, and cause edema, the accumulation of fluid within cells. The connective tissue of the uterine isthmus also undergoes structural modifications, with collagen fibers becoming thinner and more dispersed. This altered tissue, combined with enhanced blood flow and fluid, results in the distinctive softening and increased pliability. At this early stage, the growing embryo or fetus does not yet completely fill the uterine cavity, which contributes to the perceived emptiness and compressibility of the lower uterine segment.
Its Role in Pregnancy Detection
Hegar’s sign is categorized as a probable sign of pregnancy. This distinguishes it from presumptive signs, which are subjective symptoms like nausea or fatigue, and positive signs, which offer undeniable evidence such as visualizing the fetus on ultrasound or detecting a fetal heartbeat. Historically, Hegar’s sign was a valuable tool for clinicians in early pregnancy detection, especially before the widespread availability of modern diagnostic methods.
However, its clinical reliance has decreased with the advent of accurate and accessible early home pregnancy tests, which detect human chorionic gonadotropin (hCG), and early ultrasound examinations. While still a potential finding during a physical examination, Hegar’s sign is not the primary method for confirming pregnancy today. Only a qualified healthcare professional can assess for this sign during a pelvic examination.