What are all the causes of a pre-mature birth?

Answer 1

Premature birth Causes
Some women who go into preterm labor do so for unknown reasons. Other women may have a medical condition that contributes to early labor, such as:

-Ruptured amniotic sac. Normally, the fluid-filled sac that surrounds your baby in the womb ruptures during labor or just before labor begins. But sometimes the sac may rupture for no apparent reason weeks or even months before your due date. In that case, there's a high risk that labor will begin within a few days. A ruptured amniotic sac also increases the risk of infection for both you and your baby.
-Certain infections. Infections of the cervix or urinary tract are associated with preterm rupture of the membranes and preterm labor.
-Weak cervix. In a normal pregnancy, the cervix softens late in pregnancy and opens (dilates) in response to uterine contractions. But for some women, the cervix opens earlier — perhaps due to the weight of the baby and amniotic fluid. This problem can be associated with previous surgery involving the cervix, such as a dilation and curettage (D and C) or a cone biopsy. It's somewhat more likely to occur when you're pregnant with twins or other multiples.
-Certain chronic diseases. Diseases such as high blood pressure, diabetes, kidney disease and lupus may increase the risk of preterm labor. If complications arise, labor may need to be induced early.
-Uterine abnormalities. An abnormally shaped uterus may increase the risk of preterm labor.
-A previous premature delivery. Women who've had a premature delivery are at higher risk of preterm labor. For many women, though, early labor happens only once.
-Substance abuse. These include smoking, drinking alcohol or using illicit drugs.
-Malnutrition. Women who are undernourished or anemic are more likely to give birth prematurely.
-Excess amniotic fluid. Too much amniotic fluid can contribute to early labor.

Answer 2

there are lots of causes

Labor that begins before the 37th week of pregnancy is called premature or preterm labor. It is responsible for about 85% of illnesses and deaths in newborns in the United States. Premature labor is sometimes induced because of the mother's or the infant's condition. Preeclampsia/eclampsia is the most common reason for inducing labor; other reasons include fetal distress or bleeding. Common causes of spontaneous premature labor include:

abruptio placentae, or detachment of the placenta from the uterine wall
premature rupture of the amniotic sac
incompetent (too easily dilated) cervix
multiple pregnancy
abdominal or cervical surgery during the current pregnancy
placenta previa (the placenta lies between the baby and the birth canal)
Factors that increase the mother's risk of preterm labor include:

history of preterm delivery
listory of abortions or miscarriages
heavy smoking (more than 10 cigarettes per day)
history of drug abuse
exposure to diethylstilbestrol (DES), a synthetic estrogen given to treat estrogen deficiency conditions
urinary tract infection
malnutrition
height below 5 ft (1.5 m)
weight below 100 lb (45 kg)
age below 18

Answer 3

All the causes? too many to mention, some of the most common ones? here we go:
drinking, smoking, drugs, trauma, preclampsia, hormone imbalance (thyroid), a structural abnormality of the uterus, chronic illness, infection, poor nutrition.