1. What is lung maturation injection?
Lung maturation injections are a method to help fetal lungs develop more quickly, avoiding the risk of premature infants suffering respiratory failure due to underdeveloped lungs. Lung maturation drugs also reduce the risk of systemic infections, cerebral hemorrhage, developmental delays, and death in premature and malnourished infants.
Current lung maturation injections are corticosteroids. The two commonly used drugs are dexamethasone and betamethasone. Advantages of these two drugs include:
- Weak immunosuppressive ability
- Longer-lasting effect than hydrocortisone
- Good placental transfer
- Short half-life in the infant's circulatory system (approximately 40 hours).
The method of injecting corticosteroids into pregnant women to stimulate fetal lung maturation was first performed in 1972. Since then, the method has been widely applied and has achieved many successful results. Twelve randomized studies, conducted from 1972 to 1989, involved 3000 women with premature births; these women were divided into two groups, one using betamethasone and the other using a placebo. The results showed that corticosteroids help reduce the risk of respiratory distress syndrome in premature babies born before 31 weeks of pregnancy by 50 percent. In 2000, the U.S. National Academy of Medicine Workshop on the Effects of Antenatal Corticosteroid Treatment on Fetal Maturation reaffirmed the role of lung maturation injections in reducing the risk of respiratory distress syndrome, mortality, and other morbidity in preterm infants.
2. What are the effects of lung maturation drugs?
After injection into a pregnant woman's body, lung maturation drugs pass through the placenta to reach the fetus. The effects of these drugs are:
• To stimulate surfactant synthesis and release into the fetal alveoli. In normal pregnancy, surfactant, a substance that reduces surface tension in the alveoli, actively appears only around 32 weeks of gestation. This helps keep the alveoli open for gas exchange after birth. A lack of surfactant increases the risk of collapsed lungs and acute respiratory distress syndrome in newborns.
• To stimulate increased lung volume and reduce lung fluid.
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3. In what cases is a lung maturity injection administered?
A lung maturity injection is administered when a doctor determines that a pregnant woman is exhibiting signs of premature labor or is at high risk of premature labor. Signs suggestive of premature labor risk include:
- Frequent, painful uterine contractions
- Vaginal bleeding or pink mucus, lower back pain, or abdominal pressure
- Cervical changes noted on examination
- Ruptured membranes, or pelvic pain
Some common causes of premature labor are:
- Congenital uterine malformations, cervical incompetence, a short cervix, uterine fibroids, vaginal infections, urinary tract infections, and a history of premature labor in the pregnant woman
Causes from the fetus include: Multiple pregnancies, polyhydramnios, ruptured membranes, amniotic fluid leakage, amniotic infection, fetal anomalies, and in vitro fertilization.
However, more than 50% of premature births have no identifiable cause; therefore, pregnant women should have regular checkups so doctors can monitor their health. If unusual signs occur, they should seek care at a facility with obstetrics and gynecology services for timely examination, treatment, and a fetal lung maturity injection, if necessary.
4. When should lung maturity injections be given?
Lung maturity injections are given between the 24th and 34th weeks of pregnancy. If the pregnant woman has not given birth within 7 days of the injection and remains at risk of premature birth in the next 7 days, a booster injection will be given.
The dosage for each injection is as follows:
- Betamethasone: 12 mg/intramuscular injection, 2 injections, 24 hours apart.
- Dexamethasone: 6 mg/intramuscular injection, 4 injections, 12 hours apart.
Lung maturity injections are not recommended routinely. If the fetus is over 34 weeks old, lung maturity injections are unnecessary because the drugs are no longer effective at this time.
5. What side effects can lung maturation injections cause?
In addition to the drug's benefits, corticosteroid lung maturation injections can also cause side effects affecting the mother's and fetus's health, such as:
- Adrenal insufficiency in the mother; adrenal insufficiency in newborns is rare.
- Anaphylactic shock, allergies, hypotension, and an increased risk of infection in the mother.
- Hyperglycemia, starting with the first injection and lasting for about five days. Therefore, pregnant women should be screened for gestational diabetes to avoid uncontrolled blood sugar levels.
- Three or more doses of betamethasone may be associated with childhood hyperactivity. Multiple doses of dexamethasone may cause fetal neurotoxicity.
Because of these risks, lung maturation injections should only be administered as prescribed by a doctor. Pregnant women should be closely monitored after injection to prevent complications. If you have a history of premature birth or signs of premature labor, have regular prenatal checkups and comprehensive prenatal care so your doctor can monitor, treat, and limit diseases affecting your and your fetus's health.
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