Prematurity is high on the list of parental anxieties. But what exactly do we know about the development of these preterm babies? What are the stages of prematurity? What can be the consequences of an early birth? The answers to your questions with our experts.

The definition of prematurity

We call a “premature” child a baby born before 37 weeks of amenorrhea or SA (since the first day of the last menstrual period).

"Before 37 weeks of amenorrhea (SA) - that is to say 37 weeks after the end of the last period - a birth is said to be premature", confirms Dr Jean-François Magny, head of the neonatology department at the Necker Hospital, to draw the first outlines of prematurity. "You should know that a child is born at term at 41 SA. On the other hand, at less than 24 SA, the fetus is mostly non-viable".

Inserm recalls in its file on premature children (Source 1) that "about 50% of premature births are spontaneous, due to early contractions, the cause of which is rarely identified, or premature rupture of the membranes (these ruptures being sometimes of infectious origin)".

What is a very premature baby?

Extreme prematurity corresponding to a birth occurring between the 28th and 32nd SA (6 months to 7 months of pregnancy), and very extreme prematurity for births occurring before 28 weeks, below 6 months of pregnancy. The risks are all the greater for large and very large premature babies.

Childbirth: what are the causes of premature birth?

According to Dr. Magny, prematurity is plural. "These preterm deliveries can be spontaneous or induced."

In the first case (on average 60% of premature deliveries according to Inserm), an infection or a rupture of the water bag can trigger the mother's labor (generally around the fifth or sixth month of pregnancy).

In the second case, the medical team chooses to induce the delivery, “if they judge that there is any risk for the mother or the unborn child. »

Other possible causes of preterm labor include:

genitourinary or generalized infections;

abnormalities of the uterus and placenta (such as placenta previa which can be complicated by hemorrhage);

maternal diabetes

retroplacental hematoma (premature detachment of the placenta accompanied by a hematoma).

"Severe hypertension represents around 20% of the reasons for giving birth before 32 weeks of pregnancy", adds Inserm (source 1). In 30% of cases, we do not know why the child is born prematurely.

Are there women or situations at risk?

Apart from medical causes, there are aggravating risk factors that can give birth to a premature child. First of all, there is the age of the woman, the higher it is, the higher the risk increases. Multiple pregnancies also rarely come to term.

As for the consumption of tobacco during pregnancy, it multiplies by three the rate of prematurity. We also know that alcohol is a factor that can disrupt the neurological development of your future baby, but it also increases premature births.

Other risk factors, such as fatigue accumulated during difficult working conditions or exhausting housework, favor them. Thus, "the rate of prematurity is twice lower among female executives than in the worker and employee category", notes Inserm .

What weight for a premature baby?

Premature infants can be classified into three categories:

From 33 to 37 SA, it is an average prematurity that happens most often today. The baby seems more fragile, but does not require great care, just significant monitoring by the maternity pediatrician. The vital prognosis is not engaged, but it is still placed in an incubator to be better protected;

From 28 to 32 SA, it is very premature. These babies require specific neonatology care (level 2 or 3 maternity). Medical assistance is put in place because their organs are still too immature.

From 24 to 28 SA, babies are called “very preterm”. In level 3 maternity, they are directly placed in intensive care. They have no autonomy. Birth weight matters. The limit of viability is considered to be between 500 and 600 grams.

Differentiating the stages of gestation is not trivial, because the care of the child depends on its stage of prematurity. Even if nothing is sewn with white thread, we find overall that the earlier the birth, the higher the risk of sequelae during the child's development.

"Premature babies are placed in an incubator to keep them at 34°/35° C, a temperature equivalent to that of the mother's belly. Children can leave the incubator from 2 kg", details Inserm. Extremely premature and very premature babies are transferred to the neonatal intensive care unit, then referred to intensive care, then to the neonatology service when their state of health is stable.

Research is continuing to further improve the care of these children who come into the world too early.

From how many weeks a baby is viable?

Generally, a child can be discharged from the hospital when he has become autonomous from the respiratory and digestive point of view. Otherwise, it is usually considered that a child is viable from 23 to 24 SA.

What are the risks for a premature baby?

When he is born, the organs of a premature child are not all ready to face extra-uterine life. "This mainly concerns four organs: the brain, the lungs, the digestive tract and the arterial canal", specifies Inserm (source 1). The consequences differ according to its stage of prematurity.

Among the consequences on the four organs of average premature babies born at 37 weeks of amenorrhea (SA), we can cite:

immaturity of the central nervous system;

pulmonary immaturity;

cardiorespiratory immaturity;

digestive immaturity (especially necrotizing enterocolitis in newborns).

Regarding the future of medium premature babies, Dr. Magny wants to be confident. "The prognosis is generally very good. These children have as much chance as full-term children of continuing normal development. For the extremely premature and extremely premature, the forecasts are often less encouraging".

Sequelae in very and very premature babies

An apprehension supported by the results of the Epipage 1 survey conducted by Inserm among very and extremely premature babies born in 1997 (Source 1). To obtain more convincing results, the researchers created a category of extremely preterm infants which includes all births ranging from 22 weeks (to include the rare cases of viability) to 32 weeks. According to their survey, of the 10,000 very premature babies born each year in France, 8,500 survive.

Nearly 9% of these old large prema have a motor deficiency, nearly a hundred times more than a child born at term. Figures that Dr. Magny wishes to qualify: "these motor disorders cover a very wide field. Some may be unable to walk (possible paralysis of the lower limbs), while others will have a slightly imperfect gait".

In terms of sensory deficiencies, we mainly find auditory (less than 1%) and visual (about 2%) disorders.

As for so-called cognitive disorders, these are essentially difficulties related to learning and attention. This intellectual development is ultimately the most worrying. Also according to this Epipage study, nearly 12% of formerly very premature babies have moderate to severe intellectual disabilities.

How to spot a premature birth?

Uterine contractions can be a threatening sign of premature labor. The woman feels a feeling of tension in the uterus that lasts about thirty seconds. The belly hardens. These pains resemble those of menstruation. They are abnormal if they repeat regularly within ten minutes of each other.

Put yourself to rest immediately and have yourself taken to the maternity ward where you are due to give birth. The doctor will check your cervix. If it has shortened or opened a little, the delivery could take place prematurely.

“Medical follow-up during pregnancy makes it possible to identify risk situations and detect complications likely to lead to premature delivery (growth retardation, maternal hypertension, etc.), adds Inserm (Source 1).

"In the event of a threat of premature delivery, administration of corticosteroids within 10 days prior to birth can accelerate the lung maturation of the fetus, in some cases avoid neonatal respiratory and cerebral difficulties as well as death". In addition, the mother must be referred to a type III maternity unit with a neonatal intensive care unit.

Is it possible to avoid premature births?

The goal is to continue the pregnancy for as long as possible. For this, complete rest, medication to stop uterine labor and possibly hospitalization may be necessary. It is quite possible, suddenly, to arrive at a delivery close to the term.

The doctor can also decide, in case of too large an opening of the cervix (open bite), to perform a cerclage. Under general anesthesia, we pass a very strong thread to close the cervix.