In most pregnancies, labor starts between 37 and 42 weeks after the last menstrual period. Labor is considered preterm labor when it starts before the beginning of the 37th week.
If you are noticing uterine contractions, cramping or backache:
It is not known exactly what causes labor to start. Hormones produced by both the mother and fetus play a role. Preterm labor may be a normal process that starts early for some reason. Or, it may be started by some other problem, like infection of the uterus or amniotic fluid. In most cases of preterm labor, the exact cause is not known. Half of the women who go into preterm labor have no known risk factors.
Growth and development in the last part of pregnancy is critical to the baby’s health. If preterm labor is found early enough, delivery can sometimes be prevented or postponed. This will give your baby extra time to grow and mature.
Obviously, the earlier the baby is born, the greater the risk of problems. Preterm birth, especially very preterm delivery before 30 weeks, accounts for about 75% of newborn deaths that are not related to birth defects. Even “late preterm” babies, i.e. born between 34 – 37 weeks, can have problems such as maintaining a normal body temperature. Thus, if you are planning a home birth but find yourself delivering before 37 weeks, it will be recommended that you birth in the hospital.
It can be hard to tell the difference between true labor and strong Braxton-Hicks contractions. Braxton-Hicks start at around 12 weeks of pregnancy, and increase in strength in the third trimester as the uterus gets stronger in preparation for labor. At this time, women may begin to notice that their bellies regularly get hard (especially with movement such as during exercise, or caused by fetal movement). These “practice contractions” may even be painful and regular, but usually go away within an hour or with rest. Braxton-Hicks contractions can also last for extended periods of time, even up to an hour – these are generally reassuring, unlike intermittent contractions that increase in frequency, duration or strength.
Preterm labor can only be diagnosed by finding changes in the cervix. This can sometimes be done by your careprovider doing an internal exam (inserting two fingers into your vagina to feel the cervix). Other times, in the early stages of preterm labor, ultrasound will need to be used to confirm cervical shortening and/or dilation.
