B22. Intrapartum management of preterm delivery

From greek.doctor

Preterm infants are much more susceptible to hypoxia and obstetrical trauma, partly due to the foetal skull being less resistant to pressure, immature cerebral vasoregulation, and decreased production of lung surfactant. For these reasons, more monitoring and care is necessary to prevent injuries due to these mechanisms in preterms.

Choosing mode of delivery

As with term and post-term deliveries, it’s important to determine whether one should attempt vaginal birth or opt for C-section. The choice of mode of delivery depends on the gestational age, weight, condition, lie, and whether it’s an emergency or elective situation. Practices also vary from institution to institution. Breech presentation is more common in preterm foetuses.

In general, vaginal birth is preferred in cephalic presentations, and in breech presentations in less premature (> week 34) and normal sized (< 2000 g) foetuses.

C-section is less traumatising for the foetus and carries a lower risk of hypoxia. It’s always the choice in case of maternal or foetal complications, and in breech presentation of small (< 1500 g) foetuses. It’s less traumatising for the foetus. However, during vaginal birth, the mechanical forces of the birth canal on the foetus induce lung maturation and maturation of the hypothalamic-hypophyseal-adrenal axis. During C-section, the foetus misses out on these forces which may predispose to complications.

Vaginal labour

The following measures should be taken in the first stage of labour:

  • The mother should be positioned on the back to improve uteroplacental circulation.
  • Continuous CTG should be made to monitor for hypoxia or acidosis.
  • Proper maternal analgesia (often epidural) to reduce stress, improving uteroplacental circulation.
  • The myometrium is not yet mature, which may cause irregular contractions. Oxytocin may be given to assist contractions.
  • Amniotomy should be performed late, when the cervix is fully dilated.

The following measures should be taken in the second stage of labour:

  • The second stage is the one where the most stress is imposed on the foetus, so it should not be prolonged. We should consider oxytocin and operative delivery to hasten it
    • Vacuum-assisted delivery is contraindicated in preterm labour. A special forceps may be used.
  • We should make an early and extended episiotomy, to facilitate quick delivery and prevent trauma
  • The head should be delivered gently and never pulled
  • The umbilical cord should be clamped late (> 1 minute after birth)

C-section

In case of C-section of prematures, the neonatologist and an experienced anaesthesiologist should be involved in the planning and be prepared for the foetus.

In normal cases of C-section, the incision made into the uterus is transverse. In case of C-section delivery of very young prematures (< week 28 – 32), a longitudinal incision of the uterus is made instead. This reduces the trauma the foetus experiences.