Hegar's sign is a non-sensitive indication of pregnancy

Pregnancy

Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

 in women — its absence does not exclude pregnancy. It pertains to the features of the cervix

Cervix

The cervix is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall...

 and the uterine isthmus

Uterine isthmus

The uterine isthmus is the inferior-posterior part of uterus, on its cervical end — here the uterine muscle is narrower and thinner. It connects superiorly-anteriorly to the complementary parts of the uterus: the body and the fundus....

.
It is demonstrated as softening of the uterine consistency and the possibility to palpate or compress the connection between the cervix and the fundus.

The sign is usually present from 4 to 6th week till 12 weeks of pregnancy.
It is more difficult to recognize in multiparous women.

This sign was repeatedly demonstrated and described by Ernst Ludwig Alfred Hegar

Ernst Ludwig Alfred Hegar

Ernst Ludwig Alfred Hegar, aka Alfred Hegar, was a German gynecologist famous for developing new medical tools and techniques. He was born January 6, 1830 in Darmstadt, Germany and died August 5, 1914. He was buried in Breisgau....

, a German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 gynecologist, in 1895. Hegar credited Reinl, one of his assistants, who originally described this sign in 1884.