Dr Hajisedjavadi Diagnosis of preterm labor

Clinical findings  The clinical findings of true labor (ie, contractions plus cervical change) are the same whether labor occurs preterm or at term. The following are early signs and symptoms of labor; however, they are non-specific and can be present for several hours in women who do not exhibit cervical change:

 Menstrual-like cramping  Mild, irregular contractions  Low back ache  Pressure sensation in the vagina  Vaginal discharge of mucus, which may be clear, pink, or slightly bloody (ie, mucus plug, bloody show)

 signs and symptoms signaling preterm labor, including uterine contractions, appeared only within 24 hours of preterm labor.  The American Academy of Pediatrics and the American College of Obstetricians and Gynecologists (2012) define preterm labor to be regular contractions before 37 weeks that are associated with cervical change.

Cervical Change  Cervical changes on physical examination that precede or accompany true labor include dilation, effacement, softening, and movement to a more anterior position. A short or a dilated cervix may be the first clinical manifestation of a parturition process triggered by subclinical inflammation.  The rate of cervical change distinguishes cervical ripening, which occurs over days to weeks, from true labor, in which cervical change occurs over minutes to hours.

Cervical Change  Asymptomatic cervical dilatation after midpregnancy is suspected to be a risk factor for preterm delivery, although some clinicians consider it to be a normal anatomical variant.  Although women with dilatation and effacement in the third trimester are at increased risk for preterm birth, detection does not improve pregnancy outcome.  Knowledge of antenatal cervical dilatation did not affect any pregnancy outcome related to preterm birth or the frequency of interventions for preterm labor.

Cervical Change  Transvaginal sonography is safe, highly reproducible, and more predictive than transabdominal sonographic screening   transvaginal cervical sonography is not affected by maternal obesity, cervix position, or shadowing from the fetal presenting part.

Cervical Change  The mean cervical length at 24 weeks was approximately 35 mm, and those women with progressively shorter cervices experienced increased rates of preterm birth.  Until recently, routine cervical length evaluation in women at low risk was not advocated because,like other factors associated with potentially higher preterm birth risk, no effective treatments were available. Randomized trials done to investigate vaginal progesterone use in women with short cervix.

Ambulatory Uterine Monitoring  An external tocodynamometer belted around the abdomen and connected to an electronic waist recorder allows a woman to ambulate while uterine activity is recorded.  the American College of Obstetricians and Gynecologists (1995) concluded that the use of this expensive, bulky, and timeconsuming system does not reduce preterm birth rates.  The American College of Obstetricians and Gynecologists (2012a) does not recommend home uterine activity monitoring.

Fetal fibronectin  This glycoprotein is produced in 20 different molecular forms by various cell types, including hepatocytes, fibroblasts, endothelial cells, and fetal amnion.  Present in high concentrations in maternal blood and in amnionic fluid, it is thought to function in intercellular adhesion during implantation and in maintenance of placental adherence to uterine decidua.

 Fetal fibronectin is detected in cervicovaginal secretions in women who have normal pregnancies with intact membranes at term.  It appears to reflect stromal remodeling of the cervix before labor. Lockwood (1991) reported that fibronectin detection in cervicovaginal secretions before Fetal fibronectin

 membrane rupture was a possible marker for impending preterm labor.  Fetal fibronectin is measured using an enzyme-linked immunosorbent assay, and values exceeding 50 ng/mL are considered positive.  Sample contamination by amnionic fluid and maternal blood should be avoided. Fetal fibronectin

 Interventional studies based on the use of fetal fibronectin screening in asymptomatic women have not demonstrated improved perinatal outcomes.  The American College of Obstetricians and Gynecologists does not recommend screening with fetal fibronectin tests. Fetal fibronectin

False positive results can occur due to:  ejaculate from coitus within the previous 24 hours.  grossly bloody specimen  digital cervical examination.

 Theoretically, transvaginal ultrasound examination may cause a false positive result, but in one study all 25 women with a negative baseline fFN test had a second negative fFN test post-ultrasound.  Administration of intravaginal substances, such as lubricants, medications, or douching may interfere with the assay.

Prevention of preterm labor Prevention of preterm birth has been an elusive goal. Recent reports, however, suggest that prevention in selected populations may be achievable.

Cervical Cerclage There is evidence that cerclage can reduce the risk of recurrent preterm birth/pregnancy loss in women with a prior preterm birth/pregnancy loss. The first prophylactic cerclage is used in women who have a history of recurrent midtrimester losses and who are diagnosed with cervical insufficiency. The second prophylactic cerclage is for women identified during sonographic examination to have a short cervix. The third indication is “rescue” cerclage, done emergently when cervical incompetence is recognized in women with threatened preterm labor.

Women with a cervical length < 15 mm delivered before 35 weeks. significantly less often following cerclage compared with women with no cerclage—30 versus 65 percent. This study suggests that recurrent preterm birth can be prevented in a subset of women who have a history of prior preterm births.

Thus, cerclage for sonographically detected short cervix alone has not been found to be beneficial. In contrast, women with a very short cervix, that is, < 15 mm, and a history of prior preterm birth may benefit.

Progesterone is a natural steroid produced by the corpus luteum and the placenta, whereas 17- hydroxyprogesterone caproate is a synthetic steroid. Natural progesterone suppresses myometrial contractility in strips that were obtained at cesarean delivery, whereas synthetic 17-OHPC did not. This report is an excellent source of information on the issues involved with progestin use in preterm birth.

Currently, at Parkland Hospital, we are prescribing weekly injections of 17- hydroxyprogesterone compounded by a local pharmacy for women with a prior preterm birth. In our view, all other indications for the use of progestin in the prevention of preterm birth are investigational.

Smoking cessation smokers who decrease or stop cigarette smoking will reduce their risk of preterm birth, but this has not been proven. Avoidance of cocaine In the United States, cocaine has been detected in approximately 60 percent of women in preterm labor who have positive toxicology tests. It is likely that this will reduce their risk of preterm birth, but this has not been proven.

Decrease the rate of multiple gestation from ART Multiple births are six times more likely to be preterm than singleton births.

Pessary A randomized trial reported a significant decrease in preterm birth in women with singleton pregnancies and a short cervix on ultrasound examination who were managed with a cervical pessary. In contrast, in multiple gestations, routine use of a cervical pessary did not reduce preterm birth or a composite of poor perinatal outcomes compared to nonuse.

Nutritional intervention Women with adequate nutrition and a normal body-mass index have better pregnancy outcomes than other women, which suggests that nutritional interventions may have a role in preventing preterm birth.

N-3 fatty acid supplements Low consumption of n-3 fatty acids (eg, fish oil) has been associated with a higher rate of preterm birth, but n-3 fatty acid supplementation does not appear to prevent preterm birth in women with or without a history of preterm birth:

Avoiding a short interpregnancy interval The highest risk of preterm birth appears to be in women with an interpregnancy interval of less than six months.

Bed rest and hospitalization Bed rest is often recommended for women at increased risk for preterm birth. While bed rest improves uteroplacental blood flow and can lead to a slight increase in birth weight, there is no evidence that it decreases the incidence of preterm delivery, even in women with a short cervix.

Prophylactic tocolytic drugs Prophylactic tocolytic therapy for prevention of preterm birth is not effective, although few randomized trials have been conducted.

Social support and relaxation therapy There are limited data on other interventions for reducing stress in pregnant women (eg, relaxation or mind-body therapies [eg, meditation, massage, yoga, breathing exercises, music therapy, aromatherapy]). Available trials are small and of poor quality; clear effects on birth outcome have not been proven.

Thyroid hormone In a single randomized trial of 115 pregnant euthyroid women with thyroid peroxidase antibodies, levothyroxine therapy significantly reduced the rate of preterm birth.levothyroxine Before thyroid antibody assessment or treatment can be considered in euthyroid women with history of preterm birth, further study is needed to confirm these findings.

Given antibiotic treatment of asymptomatic bacteriuria reduces the incidence of preterm delivery and low-birth-weight infants, we recommend screening pregnant women for asymptomatic Bacteriuria. Treatment of asymptomatic Trichomonas vaginalis infection does not prevent, and may even increase, the risk of preterm delivery.

Women with periodontal disease are at increased risk of preterm delivery. Periodontal disease should be treated as a component of good dental hygiene, but there are inadequate data to suggest treatment for prevention of preterm birth.

 Home uterine monitoring and self-palpation of uterine contractions:  bed rest, abstinence  prophylactic tocolytics  prophylactic antibiotic therapy  enhanced prenatal care  social support have not been proven useful for preventing preterm birth.

Cervical cerclage, reduction in occupational stress/physical exertion, and nutritional intervention may be beneficial in selected women. Women with short cervical length appear to benefit from treatment with vaginal progesterone, a cerclage, or a pessary.