Premature delivery or preterm birth is a significant cause of multiple complications and even death in new born babies. Preterm labour is defined as the onset of labour before the 37th completed weeks (< 259 days) of pregnancy, counting from the first day of the last menstrual period, regardless of the birth weight. The lower limit of gestation is not uniformly defined; whereas in some developed countries it has been brought down to 22 weeks, in developing countries it is 28 weeks. The prevalence of preterm birth widely varies and ranges between 1 in 20 to 1 in 10 pregnancies. The World Health Organization in 2010 gave the global burden of preterm birth to be 5-18% across 184 countries of the world and that of Nigeria was less than 15%
RISK FACTORS AND CAUSES OF PRETERM LABOUR
Spontaneous preterm birth occurs as the result of multiple aetiologies that can occur alone or in combination. The risk factor and causes of preterm birth are;
- Maternal age <18 or >40years
- History of a previous spontaneous preterm birth or abortion
- Short inter-pregnancy interval; interval from last delivery to the next conception <14months
- Assisted conception
- Cigarette smoking and substance abuse
- Poor nutrition
- Low pre-pregnancy weight; body mass index, <19.6kg/m2
- Uterine factors; Uterine anomaly, Caesarean section, previous cervical laceration, Large loop excision of the transformation zone (a conservative treatment for abnormal pap smear; a screening test for cervical cancer)
- Placental disorders; Placenta previae, abruptio placenta
- Medical disorders; pre-gestational or gestational diabetes and hypertension, seizures, thromboembolism, connective tissue disorders, asthma and chronic bronchitis, maternal HIV, Infection, cholestasis, obesity.
- Fetal disorders; Fetal compromise, chronic poor fetal growth, acute fetal distress, polyhydramnios, oligohydramnios, hydrops, blood group alloimmunization, Birth defects, pregnancy with more than one babies.
SYMPTOMS AND SIGNS OF PRETERM LABOUR
The presence of the following constitute a diagnosis of preterm labour; Regular uterine contractions with or without pain (at least one in every 10 minutes), Pelvic pressure, lower backache and/or vaginal discharge or bleeding, cervical dilatation (> 2 cm), Length of the cervix (measured by transvaginal ultrasound scan) < 2.5 cm and funneling of the internal cervical os. It is better to over diagnose preterm labour than to ignore the possibility of its presence.
TREATMENT OF PRETERM LABOUR
Decisions regarding what to do are made based on how old is the pregnancy, estimated weight of the baby, and existence of contraindications to suppressing preterm labour. These contraindication are;
- Maternal; severe hypertension, pulmonary or cardiac disease, advanced cervical dilatation >4cm, maternal bleeding.
- Fetal; intrauterine fetal death, intrauterine growth restriction, intrauterine infection, fetal distress, estimated fetal weight ≥2.5kg.
Treatment with medications to inhibit labour after contractions and cervical change are well established or membranes have ruptured does not prolong pregnancy sufficiently to allow further intrauterine growth and maturation. However, their use can often delay preterm birth long enough to permit four interventions that have been shown to reduce neonatal morbidity and mortality such as:
- Antenatal transfer of the mother and fetus to the most appropriate hospital
- Antibiotics in labour to prevent neonatal infection with the group B streptococcus (GBS)
- Antenatal administration of glucocorticoids (dexamethasone) to the mother to reduce neonatal morbidity and mortality due to respiratory distress syndrome(RDS) from immature lung, bleeding into the brain cavity and other causes
- Administration of maternal magnesium sulfate at the time of preterm birth before 32 weeks for neuroprotection to reduce the incidence of cerebral palsy.
Delivery could be via vaginal or caesarean section. For babies in breech presentation (coming with the bum) there are intuitive reasons for caesarean delivery to avoid possible entrapment of the head after delivery of the body. For early preterm delivery (<32weeks) there is no difference in outcome between vagina or caesarean delivery. For babies ≥32 weeks, caesarean section will be the most preferred option and will be offered to you.
COMPLICATIONS OF PRETERM BIRTH
The complication of preterm birth is prematurity and it associated complication such as;
- Respiratory distress syndrome; collapse of the new born lungs due to impaired production of a substance called surfactant that keeps the lungs patent during breathing.
- Apnoea; the new born breathing cease for more than 20 seconds.
- Anaemia of prematurity and risk of multiple blood transfusion
- Low blood sugar
- Low body temperature
- Necrotizing enterocolitis; damage to the intestines that might range from injury to death of some parts or perforation.
- Neonatal jaundice
- Intraventricular haemorrhage; bleeding into the brain cavity.
- Sepsis; dysregulated response to infection resulting in injury to multiple organs
The risk of recurrent preterm birth may be reduced in women with a prior preterm birth and/or a short cervix <2.5cm by administration of prophylactic supplemental progesterone, and by selective use of cervical cerclage.