A woman who goes to see her doctor or midwife because she suspects pregnancy will be asked when her last period took place. The reason for this is simple: if the woman is indeed pregnant, the due date can be estimated based on the last known period. Doctors take the date of the last period and count forward 40 weeks to determine the baby's due date (40 weeks is the average gestation period for human babies). From this estimated due date, doctors can also determine whether a baby is preterm at birth.
As a general rule, babies born anywhere between the 37th and 42nd week are considered full-term babies. A baby is preterm if born prior to the 37th week. Believe it or not, preterm birth is actually more common than most people know. The UK sees about 80,000 such births every year while as many as 15 million children are born preterm around the world.
The implications of preterm birth are rather extensive for both mother and baby. Therefore, to make things easier for the medical community to address, preterm births have been divided into three classifications, as dictated by the World Health Organisation:
Data shows that the vast majority of preterm babies born in the West are moderate to light preterm. In other words, they are born at 32 weeks are later. Fortunately, babies born at this point enjoy survival rates in excess of 90% in Europe and North America. Experts cite our high quality of healthcare as one of the primary reasons for this.
At the other end of the scale, babies born between 23 and 28 weeks have a significantly lower chance of survival. At 23 weeks the survival rate is about 15%. Any preterm delivery earlier than 23 weeks has a near zero survival rate. For this reason, 23 weeks seems to be the cut-off at which doctors are willing to aggressively try to save a baby's life.
There are two main differences between preterm and full-term births, the first being the potential for complications. Obviously, there can be complications with any pregnancy or birth regardless of how long it goes. But with preterm births, the risk of complications increases as the term of the pregnancy goes down.
For example, a preterm birth can be instigated by a condition known as pre-eclampsia. This condition causes hypertension and protein build-up in the mother's body. While most cases of pre-eclampsia do not cause any trouble, a severe case left untreated could lead to mum developing eclampsia fits, liver problems, or cardiovascular problems. Complications involving the baby can include stunted growth, low birth weight, and neonatal respiratory distress.
A mother being admitted to the hospital experiencing symptoms of preterm labour will be thoroughly evaluated by a medical team to determine the risk of complications. The most important thing to know is that a high risk of complications that could endanger the life of either mother or baby could result in a caesarean delivery. This is a surgical procedure resulting in delivery through an incision in the uterus.
The other main difference between a preterm and full-term birth is the potential of permanent disability. All preterm babies are at risk of disability, but risks are more severe with shorter terms. Most of the disabilities we do see with preterm babies are directly related to baby's body not having had time to fully develop before birth.
Among the biggest concerns is lung deficiency. If lungs are not developed fully enough to allow the baby to breathe by itself, the results could be devastating. Inadequate lung development can lead to permanent breathing problems and dangerous infections. Doctors will attempt to administer steroids to stimulate lung growth if a baby is at risk of preterm birth.
Another big concern is oxygen deprivation that might occur during labour and delivery. For obvious reasons, preterm babies are more susceptible to this problem. If oxygen deprivation lasts long enough, it could result in brain damage that could manifest itself in any number of developmental disabilities.
Other potential problems faced by preterm babies include cardiovascular disease, cerebral palsy, renal disease, vision and hearing problems, cognitive disabilities, and an inability to thrive.
Please do not assume that every preterm birth results in complications for mum or permanent disabilities for baby. That is certainly not the case. In fact, the majority of preterm babies born after the 32nd week go on to live completely normal lives.
Despite millions of babies being born early every year, science has not been able to say definitively what causes premature birth. The vast majority of preterm births occur spontaneously and without any known cause. When a suspected cause can be identified, it could be anything from diabetes to high blood pressure to some sort of trauma suffered by the mother or her child. A few studies even suggest there may be a genetic influence in some cases.
Soon-to-be parents should know that the best way to increase the likelihood of a healthy, full-term birth is to protect the health of both mother and baby during pregnancy. This includes eating correctly, avoiding alcohol and drugs, avoiding tobacco, and taking care not to expose mother or baby to any unnecessary risks. If preterm labour should occur anyway, parents in the UK can rest assured that our medical system is more than capable of handling the situation.