Some pregnant women hear from the 20-week scan that there is a possible shortened cervix. A shortened cervical neck is shorter than 30 mm. In many countries, the length of the uterus is not yet routinely measured in pregnant women who do not have an increased risk of an early child.
Studies have shown that the risk of premature birth in women with a shortened cervix is greater compared to women with a normal length of uterus. In daughters of women who have used the DES hormone, the cervix is also a little shorter.
Pregnancy with a short cervix and early onset can be treated with medication. Progesterone is prescribed for this purpose.
A short cervical neck does not mean your baby will be premature, but is associated with an increased risk.
From angelababy In Q&A