Communication and Support
A holistic approach to the situation is essential. Sympathy, explanations, and reassurance are mandatory. There are two vital areas of communication in the management of threatened preterm labor or PPROM. Communication with the woman and her family ensures that they have a full understanding of the risks involved and enables a clear management plan to be discussed. Communication with the neonatal unit staff ensures that adequate and appropriate resources are available at the time of delivery. Parents often also appreciate the opportunity to have discussed the care of their baby with the neonatology staff in advance of delivery.
Current evidence shows that a single course of maternal steroids (two injections 12-24 hours apart) given between 24+0 and 34+6 weeks’ gestation and received within 7 days of delivery results in markedly improved neonatal outcomes. This is primarily because of a reduction in neonatal respiratory distress syndrome (RDS). Maximum benefit from the injection is seen after 48 hours. Courses received less than 48 hours or more than 7 days before delivery still lead to benefit. Observational data suggests benefit at 23 weeks but evidence is weak for 22 weeks. Nonetheless, they are not indicated when palliative neonatal care is chosen or before viability. The steroids most commonly used are 12 mg of either betamethasone or dexamethasone.
There is considerable reassuring evidence about the long-term safety of single courses of maternal steroids, with pediatric follow-up into the teenage years. However, there have been concerns about adverse consequences of multiple dosing. Similar to antibiotics, steroids have the potential for harm in pregnancy and should be used carefully. Decisions about second courses of steroids should be made by senior clinicians and consider the gestational age, likelihood of delivery in the next 48 hours, interval since last course. A commonsense approach at present is to limit the number of courses to two with at least 4 weeks between the courses.
The Canadian Preterm Labor Trial remains the most influential tocolytic trial to date. It concluded that ritodrine, a beta-agonist that relaxes smooth muscle, had no significant benefit on perinatal mortality or the prolongation of pregnancy to term. However, it was able to reduce the number of women delivering within 2 days by 40 percent. This 48-hour window of opportunity is the sole reason for using tocolytics. Beta-agonists have significant maternal side effects, and maternal deaths from acute cardiopulmonary compromise are described. Other smooth muscle relaxants used to treat preterm labor include nifedipine and glyceryl trinitrate. The former has become popular because it is inexpensive, is given orally, and has a low side effect profile. A common nifedipine dosing regime is 20 mg orally followed by 10 to 20 mg every 6 to 8 hours to a maximum daily dose of 60 mg. The oxytocin antagonist atosiban has a product license in some countries but not in North America. Although side effects are seen less frequently than with ritodrine, the cost is much higher. Because prostaglandins appear to be one of the pivotal chemicals involved in parturition, nonsteroidal anti-inflammatory drugs such as indomethacin have attracted considerable interest as tocolytics. They have been associated with significant fetal cardiovascular side effects, although these can be mitigated by limiting them to short-term use (<72 hours) and only at gestational ages less than 30 weeks.
Unfortunately, despite a multitude of pharmacologic approaches, no tocolytic medication has yet been conclusively shown to improve neonatal outcomes. Presently, the role for tocolysis is to allow a course of steroids for fetal lung maturation to be completed and to facilitate transfer of the undelivered mother to a unit able to provide appropriate neonatal care if delivery occurs. They should be used with caution in the presence of ruptured membranes.
Magnesium sulphate has been shown to lead to a reduction in cerebral palsy after very preterm birth. Not surprisingly, it has the greatest benefit at the earliest gestations. The upper gestational age limit is suggested to be 33+6 weeks. A 4-gram loading dose is used followed by maintenance therapy for up to 24 hours. Treatment should only be initiated in patients at imminent risk of preterm birth, and there is currently no evidence to support repeat courses.
Broad-spectrum antibiotics offering aerobic and anaerobic coverage are necessary in the presence of overt clinical infection, such as chorioamnionitis. The role of antibiotics in the absence of clinical signs of infection is much less clear.
The MRC Oracle Study initially concluded that the use of prophylactic antibiotics in uncomplicated preterm labor before 37 weeks with intact membranes did not confer any short-term neonatal benefit. Worryingly, subsequent long-term follow-up of survivors actually showed a significant increase in neurodevelopmental disability in those who received either erythromycin or co-amoxiclav.
In PPROM, the same study concluded that a 10-day course of erythromycin led to improved short-term neonatal outcomes. A much smaller U.S. study that only enrolled women below 32 weeks with PPROM also confirmed the benefit of antibiotics in the short term.
Most North American centers continue to give intrapartum antibiotics to women in preterm labor unless GBS status is known to be negative. For reasons that are unclear, the risk of early-onset neonatal disease appears much less in other countries, such as the United Kingdom.
After 24 weeks, maternal steroid therapy can suppress both fetal activity and heart rate variability, although Doppler studies are not influenced. Whenever possible, the presentation in preterm labor should be confirmed by ultrasound, because clinical palpation is notoriously unreliable. An estimated fetal weight, particularly before 28 weeks, can be helpful. Preterm infants have less reserve to tolerate the stress of labor, particularly in the presence of oligohydramnios. Therefore, continuous fetal monitoring may be required, although there may be considerable difficulties interpreting the fetal heart rate pattern in extremely preterm infants. At the extremes of viability, parents may decline intervention for suspected fetal compromise or aggressive resuscitation of the newborn. In these cases, continuous monitoring would be inappropriate.
If local resources are unable to care for a viable neonate, in utero transfer to a unit with adequate neonatal facilities is recommended. It is generally accepted that this will improve the outcome for babies, particularly before 30 weeks of gestation. However, one must be careful not to convert a hospital delivery into a roadside one. A repeat assessment immediately before transfer is mandatory.
Randomized trials of social support in the United Kingdom failed to improve pregnancy outcomes, and in some studies, hospitalization for bed rest led to an increase in preterm birth. Roles for sexual abstinence and/or psychological support are no clearer. Patients should be informed that there is no evidence that their activity level influences outcome. The Society for Maternal-Fetal Medicine guidelines on activity restriction “recommend against the use of any type of activity restriction in pregnant women at risk of preterm birth.” This should be tempered by the realization that there is a natural tendency to analyze the days leading up to a preterm birth, looking for triggers. Patients should be somewhat cautious and avoid overexertion or extreme stress, if only to minimize subsequent feelings of guilt, however misplaced.
Emergency Cervical Cerclage
When a patient presents with an open cervical os and bulging membranes before viability, the idea of closing the cervix by passing a stitch around it seems logical. However, the results of emergency cervical cerclage are poor and are related to the cervical dilatation at insertion. The procedure itself can be technically challenging. A dilatation of more than 3 cm with an effaced cervix poses extreme difficulties even for the most experienced operator. Every effort should be made to detect and treat other causes of the uterine instability. If persistent placental bleeding is leading to secondary opening of the cervix, suturing the cervix clearly does not address the primary issue and is unlikely to be successful. Bleeding, contractions, and infection are all contraindications to cerclage. Depending on the initial dilatation of the cervix, the chance of the pregnancy proceeding beyond 26 weeks may be less than 50 percent.
Induction or Augmentation
In some cases, it may be judged appropriate to hasten delivery because the maternal or fetal risks of continuing the pregnancy are judged too high. After 24 weeks, if there is no evidence of acute maternal or fetal compromise, induction with milder prostaglandins, such as Cervidil or conventional-dose oxytocin, can considered as an alternative to a planned cesarean section. Great care must be exercised if there is already clinical evidence of chorioamnionitis. In these cases, delay in ending the pregnancy may lead to worsening infection and consequent morbidity for both the mother and baby. Augmenting labor may be the most appropriate management. After extremely or very preterm PPROM, an initial period of conservative management is commonly undertaken. Close observation for evidence of clinical chorioamnionitis, such as maternal fever, uterine tenderness, and fetal tachycardia, is necessary. There is no evidence that serial WBC counts or CRP levels add to clinical examination. There is evidence appearing that supports active management after 33 completed weeks, particularly after a course of steroids has been completed.
For intrapartum analgesia, an epidural is frequently advocated. Postulated benefits include avoiding expulsive efforts before full dilatation or a precipitous delivery, a relaxed pelvic floor and perineum, and the ability to proceed quickly to abdominal delivery.
Many clinicians believe that the combination of high fetal morbidity and mortality; difficulty in diagnosing intrapartum hypoxia or acidosis; and maternal risk of complications, both intraoperatively and in subsequent pregnancies, do not justify cesarean section for fetal indications before 24 weeks. As gestation advances, both neonatal outcomes and the ability to diagnose fetal compromise improve, and intervention for fetal reasons becomes appropriate. It is often appropriate to leave the membranes intact even if oxytocin is required. There is little risk of dystocia, and an intact gestation sac cushions both the fetal head and umbilical cord. The safety of preterm breech vaginal delivery between 26+0 and 36+6 weeks is often questioned. Cesarean section should be considered, although evidence to support this as a routine policy remains less than ideal.
At the earliest gestations and in the presence of oligohydramnios, the lower segment is often poorly formed. Vertical uterine incisions may be necessary. This “classical” uterine incision carries an up to 5 percent risk of uterine rupture in subsequent pregnancies, some of which will occur before the onset of labor.
Ideally, delay cord clamping by around 60 seconds for preterm babies, if the mother and baby are stable. Ensure the baby is dried and kept warm during this interval.