How is preterm labor treated?

Updated: Dec 17, 2018
  • Author: Michael G Ross, MD, MPH; Chief Editor: Carl V Smith, MD  more...
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Answer

Answer

Preterm labor may be difficult to diagnose and a potential exists for overtreatment of uterine irritability. Tocolytic agents, while generally safe in appropriate dosages with proper clinical monitoring, have potential morbidity and should only be used after consideration of the risks and benefits of such use. Neonatal morbidity and mortality are greatly affected by gestational age, especially when the pregnancy is less than 28 weeks’ gestation. Tocolysis should be used with caution when the fetus is previable because the expected prolongation of the pregnancy is limited, and the neonate has a minimal chance of survival at less than 23 weeks. The likelihood of survival is further reduced in the presence of significant medical complications, such as intra-amniotic infection (IAI) at these ages.

On the other hand, the risk of neonatal mortality and morbidity is low after 34 completed weeks of gestation; although a trial of acute tocolysis may be initiated, aggressive tocolytic therapy is generally not recommended beyond 34 weeks, due to potential maternal complications. Between 24 and 33 weeks’ gestation, benefits of tocolytic therapy are generally accepted to outweigh the risk of maternal and/or fetal complications and these agents should be initiated provided no contraindications exist. Although aggressive tocolysis is not typically used beyond 34 weeks’ gestation, clinicians are advised not to deliver patients at this gestation without indication because of a higher risk of neonatal morbidity in infants born at 34-36 weeks’ gestation compared with deliveries at 37-40 weeks’ gestation. [20]

The following table depicts survival, major short-term morbidity, and intact long-term survival by gestational age.

Table. Neonatal Morbidity and Mortality by Gestational Age (Open Table in a new window)

Gestational Age, wk

Survival

Respiratory Distress Syndrome

Intraventricular Hemorrhage

Sepsis

Necrotizing Enterocolitis

Intact

24

40%

70%

25%

25%

8%

5%

25

70%

90%

30%

29%

17%

50%

26

75%

93%

30%

30%

11%

60%

27

80%

84%

16%

36%

10%

70%

28

90%

65%

4%

25%

25%

80%

29

92%

53%

3%

25%

14%

85%

30

93%

55%

2%

11%

15%

90%

31

94%

37%

2%

14%

8%

93%

32

95%

28%

1%

3%

6%

95%

33

96%

34%

0%

5%

2%

96%

34

97%

14%

0%

4%

3%

97%

 

Tocolytic agents have not proven to be efficacious in preventing preterm birth or reducing neonatal mortality or morbidity. The primary purpose of tocolytic therapy today is to delay delivery for 48 hours to allow the maximum benefit of glucocorticoids to decrease the incidence of RDS. While tocolytics can be successful for 48 hours when membranes are intact, some clinical studies suggest that the effectiveness of tocolytics is only slightly better than bedrest and hydration, both of which have fewer adverse effects than tocolytic therapy.


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