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Premature (Preterm) Labour

Introduction

The date of gestation (pregnancy) is calculated from the first day of the last menstrual period. A term pregnancy is defined as those that reaches between 37 weeks to 42 weeks. Thus, premature or preterm labour is defined as labour that occurs before 37 weeks of pregnancy.

In Malaysia, the prevalence of premature labour was approximately 10% in the year 1998. Not all women who have premature labour will deliver their baby early. 30% to 50% of mothers who are diagnosed with premature labour, will go on to continue with the pregnancy and deliver their baby at term. That means a significant proportion of premature labour subsides either naturally or through the use of medications to suppress the contractions.

Causes

The cause of premature labour is unknown in the majority of cases. However, about 20% of cases are actually planned early deliveries. These are instances where there is a significant medical condition involving the mother and/or her baby/babies, which warrant an earlier delivery. Some examples includes cases of severe hypertensive disease or diabetes in pregnancy which may affect both the mother and her baby.

It is difficult to predict who will or when a mother will develop premature labour. However, there are factors that increases a woman’s risk. These risk factors includes;

  1. History of previous premature deliveries
  2. Multiple pregnancies (twins or triplets)
  3. History of surgery on the cervix (e.g. cone biopsy)
  4. Some structural abnormality of the uterus
  5. Bleeding from the uterus during pregnancy (e.g. bleeding from a low lying placenta or due to the premature separation of the placenta from the uterus)
  6. Usage of illicit or illegal drug (e.g. heroine, morphine, cannabis)
  7. Cigarette smoking
  8. Uterine, vaginal or bladder infections
  9. Grossly underweight before pregnancy or poor weight gain during pregnancy
  10. Excessive amniotic fluid (polyhydraminous)
  11. Moderate to severe anemia early in the pregnancy
  12. Poor spacing between pregnancies
  13. Abdominal surgery during pregnancy
  14. Teenage pregnancy
  15.  Severe physical or psychological stress during pregnancy.

Signs and Symptoms

The early signs and symptoms may be vague, such as lower abdominal or low back pain. The mother may also have regular tightening or painless contractions. However, actual signs of symptoms or premature labour are;

  1. Appearance of ‘show’ (watery, mucus, or bloody vaginal discharge)
  2. Regular painful contractions which increases in frequency and duration
  3. Ruptured membranes “broken water”

Complications

Premature birth is a major cause of newborn complications and death. The premature newborn is at risk of medical complications or problems related to the incomplete development of its organ systems. These problems may include difficulty with breathing, staying warm, feeding, as well as injury to the eyes, intestines, and nervous system among other things. The more premature the baby, the higher the risks and severity of complications. However, with medical advancement in intensive neonatal care, the outcome of premature babies is improving all the time.

Treatment

The primary goal of treatment is to delay delivery and to allow the pregnancy to continue where possible. Where it is not contraindicated, medications to suppress the contractions may need to be given. Steroid injections should also be given to mothers between certain gestational age to promote the baby’s lung maturity and improve survival. When given time for the steroids injections to work, the incidence of some complications in premature babies would be reduced. The doctors managing the case should discuss the plan of management with the patient and her husband or partner.

Premature babies should be delivered in specialist hospitals with NICU (Neonatal Intensive Care Unit) facility. Sometimes, suppressing preterm labour to allow a patient to be transferred to a specialist hospital with NICU facility is advisable. This would also allow time for the steroid injections to work.

In specialist hospitals with good NICU facility, babies born after 32 weeks usually have good outcome. In general, the more mature the baby, the better is the outcome. However, those born less than 32 weeks or particularly if less than 1 kg at birth may have significant short term and long term medical complications.

Medications used to stop or suppress labour are called “tocolytic” agents. Some of these medications include nifedipine, atosiban, terbutaline and magnesium sulphate. Tocolytic medications are intended to delay delivery or suppress labour for a short period of time, so the duration of usage is usually limited up to 48 hours.

Up to 50% of premature labour may naturally subside by itself with bed rest or with the use of tocolytics. Depending on various clinical factors, the mother may be allowed to go home or may need to remain in the hospital. If she is allowed to return home, then appropriate counseling and clinic follow-up need to be arranged. If she is allowed to go home, she should be advised to refrain from strenuous physical activities and to come to the hospital immediately if she develop signs and symptoms of labour again.

Steroids

It is given to the mother to promote maturity of her baby’s lungs. The most commonly used steroid in Malaysia is dexamethasone and it is administered through intramuscular injections. Dexamethasone can be given either 6mg every 12 hours for a total of 4 doses or 12mg every 12 hours for a total of 2 doses. The benefit can be seen 24 hours after the first dose has been given or less than 7 days after the last dose of the medicine.

Dexamethasone will benefit a premature babies by lowering the risk of:

  • Breathing problems (respiratory distress syndrome) after birth.
  • Bleeding in the brain
  • Intestinal infection
  • Death.

Prevention

It is difficult to prevent premature labour as the cause is unknown in the majority of cases. It would be advisable to stop harmful habits such as smoking and the use of illicit/illegal drugs. There are some clinical evidence to show that progesterone supplements in the form of injection or vaginal gel can be offered to mother with a history of a previous premature birth, to prevent a recurrence of premature labour. Progesterone supplementation can be given between 16 and 26 weeks of pregnancy and continued until 36 weeks, however, there is no evidence that it is effective in women with no previous history of premature/preterm labour or in women with multiple gestations (e.g. twins).

False Labour Contractions

False labour contractions (Braxton Hicks contractions) are tightening of the uterus that occur usually less than eight times in an hour or four times every twenty minutes. It is typically irregular and painless. It is not accompanied by bleeding or vaginal discharge. Generally, it resolves with rest. These painless uterine contractions are normal and do not increase the risk of getting premature labour. Unfortunately, sometimes it is difficult to differentiate between premature labour and false labour.  The mother is advised to seek medical opinion in clinics or the nearest hospital, if these contractions does not resolve or become more frequent and painful. The doctor or nurse may ask some questions and perform a simple pelvic examination to determine if a mother is having premature labour or just tightening.

References

  • Annual Report on Perinatal Mortality, Malaysia; 1998.
  • Hospitalisation and bed rest for multiple pregnancy. Crowther CA, Han S, Cochrane Database Syst Rev. 2010
  • Green-top Guidelines No. 7: Antenatal corticosteroids to reduce neonatal morbidity or mortality (October 2010)

 

Last Reviewed : 14 November 2014
Writer : Dr. Hj. Mohamed Hatta b. Mohamed Tarmizi
Accreditor : Dr. Haris Njoo Suharjono

 

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