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Main Causes and Possible Complications
Five main clinical situations can cause birth to occur before 33 weeks:
High blood pressure and complications
Hypertension occurs when systolic blood pressure is equal to or higher than 140 mmHg and/or diastolic blood pressure is equal to or higher than 90 mmHg. Usually, we distinguish women who have known hypertension (that existed before pregnancy) from women who develop hypertension for the first time during pregnancy, which is more often the case.
Frequency: High blood pressure is present in about 20% of deliveries prior to 33 weeks.
Complications: High blood pressure can be complicated by other health issues, the most common being:
- Pre-eclampsia: Hypertension is associated with the presence of protein in the urine, a sign of kidney problems.
- Eclampsia: This rare but serious complication of hypertension causes convulsions that signal brain damage.
- Hellp syndrome: A serious complication of hypertension during pregnancy, Hellp syndrome causes liver disorders and destroys red blood cells and blood platelets.
- Retroplacental hematoma: This condition causes the placenta to detach prematurely from the uterine wall and a hematoma to form.
Bleeding (hemorrhaging)
Defined as abundant bleeding that endangers the mother and child, hemorrhaging includes:
- Placenta previa: A poorly inserted placenta (near or blocking the cervix) can be complicated by hemorrhaging.
- Retroplacental hematoma: Can occur with hypertension (see above), but also in women with no known history of hypertension.
- Other hemorrhaging occurring in the third trimester of pregnancy (bleeding whose cause is not always known).
Frequency: Hemorrhaging occurs in about 20% of deliveries before 33 weeks.
Early rupture of membranes
Premature rupture of membranes occurs when the amniotic sac holding the water breaks before full term and labour. One theory to explain PROM blames infection. Currently, it is estimated that one third of PROM cases are linked to an intrauterine infection (chorioamnionitis).
Other factors such as unfavourable socioeconomic conditions and smoking also play a role. PROM is involved in about 25 to 35% of births before 33 weeks.
Spontaneous early labour
This term describes labour that begins before the normal pregnancy term (37 weeks), although the membranes are still intact (mother’s water has not yet broken when labour begins). Once again, infections are suspected of playing a role. At least 15% of women giving birth after spontaneous premature labour have been shown to have a uterine infection (chorioamnionitis). Other events, especially difficult living conditions and stress, are also involved. Study results show that spontaneous premature labour accounts for about 25 to 30% of births before 33 weeks.
Intrauterine growth restriction
This term is used when the birth weight is too low for the baby’s gestational age. Growth curves (such as those found in the health booklet) for gestational age are used to identify the condition. Healthcare professionals can thus spot children who are not growing sufficiently in the womb. Growth delay is generally diagnosed or detected thanks to ultrasound during pregnancy (based on the growth curves). Growth delay is partly linked to abnormal blood flow between the uterus and the placenta. Since the maternal-fetal link has been weakened, the supply of nutrients and oxygen is insufficient. If the placenta is too unhealthy and the supply very inadequate, the fetus will be at serious risk. In this situation, medical teams will induce premature birth, most often by caesarean section. The link between maternal blood pressure and a growth delay in the child is therefore very common. Other causes, such as some fetal conditions (malformations or genetic disease) can worsen intrauterine growth restriction.
Possible complications of prematurity
Possible complications of prematurity
Possible complications of prematurity
Possible complications of prematurity
The condition is the most frequent health problem experienced by preterm babies, because their lungs are not yet fully developed. That’s why some babies must be placed on a respirator.
Abnormal Lung Growth
Possible complications of prematurity
Possible complications of prematurity
This complication occurs in newborns born before the 32nd week of pregnancy and who received oxygen by respirator over a long period.
Temporary Cessation of Breathing
Possible complications of prematurity
Temporary Cessation of Breathing
Since the brain is not yet full developed, breathing and heart rate are not completely controlled. Preemies therefore have respiratory and cardiac irregularities, and are often connected to a cardiorespiratory monitor that surveys their vital signs.
Gastroesophageal Reflux
Gastroesophageal Reflux
Temporary Cessation of Breathing
The muscle that opens the stomach is not yet fully developed in preemies, which enables the stomach contents to return up the esophagus. About 3 to 10% of very premature babies suffer from gastroesophageal reflux.
Jaundice
Gastroesophageal Reflux
Jaundice
Premature babies frequently have this condition because their liver is immature, and feeding is often delayed. Jaundice is treated with phototherapy.
Anemia
Gastroesophageal Reflux
Jaundice
Preemies are at greater risk of suffering from anemia, since about 80% of a baby’s iron reserves are stored during the last trimester of pregnancy. Rapid growth after birth also contributes to this risk.
Infections
Necrotizing Enterocolitis
Brain Damage
Premature babies have a greater risk of developing infections because of their fragile and permeable skin, underdeveloped immune system, low weight, and countless medical procedures. Infections can develop during pregnancy, at birth or during hospitalization, and are generally treated with antibiotics.
Brain Damage
Necrotizing Enterocolitis
Brain Damage
Brain hemorrhaging affects 30% of babies born before 30 weeks or weighing less than 1500 grams, since some brain zones are fragile and blood vessels may bleed if the pressure increases. The consequences vary according to the seriousness of the bleeding. Simple interventions can prevent this hemorrhaging, however.
Necrotizing Enterocolitis
Necrotizing Enterocolitis
Necrotizing Enterocolitis
An inflammation of the intestine that can be fatal, this complication occurs mainly within the first two weeks after birth, and affects 5 to 10% of babies weighing less than 1500 g.
Heart Malformation
Heart Malformation
Necrotizing Enterocolitis
Some preterm children may suffer from a heart murmur, because their arterial canal (ductus arteriosus) has not had time to close.
Deafness
Heart Malformation
Retinopathy
Hearing is often not fully developed in preemies. It is estimated that 2 to 10% of babies born at or before 32 weeks of pregnancy have hearing problems.
Retinopathy
Heart Malformation
Retinopathy
his condition affecting preterm babies’ eyes consists of abnormal growth of the eye blood vessels, which makes the retina (the membrane covering the back of the eye) detach. The principal cause is administration of oxygen. Retinopathy affects mainly babies born before 28 weeks and can sometimes cause loss of vision.
Because of these countless possible complications, a premature baby may be kept in the hospital’s neonatal unit for weeks and even months after birth. For example, a baby born before the 28th week of pregnancy will stay at the hospital until the original due date. A baby born between the 35th and 36th week will leave the hospital after the usual time period.
Common winter illnesses
Respiratory syncytial virus (RSV) infection can be serious and affects the lungs and airways.
It is most common in preemies and remains the most common cause of lower respiratory tract infection.
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