Definition
As premature contractions one calls efforts to the birth before the completed 37th week of pregnancy, i.e. up to including 36 + 6 by beginning contractions. This is the borderline to premature birth. 1:30 – 1:50 births, involved in approx.
30-50% of all premature births (premature labor). The development of labor (preterm labor) is based on the body’s own hormones, oxytocin and prostaglandins. Oxytocin is produced in the hypothalamus and leads to contraction of the uterus by binding to receptors.
In the course of pregnancy, the receptors in the uterus muscles increase, so that sensitivity increases. The pathogenesis of local infections lies in the formation of a hormone produced naturally in the body, prostaglandin, which on the one hand leads directly to uterine contractions (= contractions) by activating the smooth muscles, but on the other hand also softens the cervix so that it opens. The cervix is divided into an inner and an outer cervix and thus frames the cervix (= cervical canal).
It opens outwards into the vagina and inwards into the uterus. The softening and thus easier opening is a natural process during birth. Prostaglandins are formed due to the increased release of an enzyme, phospholipase A2, during an inflammatory reaction.
This then leads to an increased synthesis of arachidonic acid, which in turn is converted into prostaglandins (premature contractions). The pathogenesis of labor (premature labor) in multiple pregnancies and polyhydramnios is that the muscle layer of the uterus (= myometrium) is stretched too far. The causes for the onset of premature labor are manifold.
Infections are most frequently involved. These can be generalised infections (e.g. urinary tract infections) or fever, but also local infections such as inflammation in the vagina (=colpitis), in the cervix (=cervicitis) or in the uterus directly (=intrauterine). Mental/physical overstrain or certain foods are also mentioned as reasons for premature labor.
A high risk is also associated with multiple pregnancies or problems with the placenta, which can be either placental insufficiency or placental detachment. A calcified placenta can also lead to premature labor. In this case, the reduced blood flow to the fetus and its reduced supply of nutrients via the placenta is the decisive reason for the induction of labor.
An excessive amount of amniotic fluid (=polyhydramnion) can also be considered a cause of premature labor. An excessive amount of amniotic fluid (=polyhydramnion) can also be considered as a cause of premature labor. Depending on the week of pregnancy, there are standard values for what type of contractions (premature labor) and how many per day or per hour are considered normal.
Increased frequency of occurrence speaks for preterm labor, in addition there can be relatively unspecific symptoms such as back pain, pulling in the abdomen, hardening of the abdomen or altered discharge. If only cramps without pain or discharge occur, it may also be just exercise contractions. Normal is up to 10 contractions in 24 hours, up to 30 weeks of pregnancy less than 3, above that less than 5 contractions per hour. From the 20th week of pregnancy onwards, uncontrolled, weak contractions (so-called Alvarez waves of up to 20 mmHg) or uterine contractions of up to 30 mmHg with subsequent pause in labour (=Braxton Hicks contractions) can occur (premature contractions).
