EXPLORE PAST ISSUES
Prematurity
Vol. 21 No 1 | Autumn 2019
Feature
Practicalities of preterm delivery
Dr Hannah Sylvester
FRANZCOG trainee
Dr Han-Shin Lee
BMedSci(Hons), MBBS(Hons), FRANZCOG, DDU, CMFM

The advent of contemporary neonatal intensive care since the 1970s has not only improved the survival of preterm infants, but also progressively moved the viability goalpost towards an earlier gestational age. In Australia, 8.6 per cent of all babies, 14 per cent Indigenous, are born preterm.1 These figures increase in multiple gestations, accounting for 63 per cent of twins and 100 per cent of higher order multiples. Three out of four preterm births occur spontaneously. Delivery of the preterm fetus is fraught with peril, due to the potential maternal and fetal morbidity and mortality. It is therefore vital that we are well-equipped to bring these tiny babies into the world in the safest way possible.

Due to the unpredictable nature of preterm labour, prompt decisions about the mode of delivery often need to be made. These are based on multiple factors, such as maternal and fetal wellbeing, lifelong morbidity of the preterm infant, the agreed gestation of viability between the parents and the treating team, parental wishes, future reproductive implications, contraindications to vaginal birth, and so forth.

In light of the paucity of evidence on the optimal mode of delivery, in the context of extremely preterm birth (less than 28 weeks) and very preterm birth (28–32 weeks), as defined by the World Health Organization,2 we examine the various modes of delivery of the early preterm infant and their benefits and drawbacks.

Instrumental delivery

The indications, requirements and maternal risk factors of performing a preterm instrumental delivery are similar to their termed counterparts. Both forceps and vacuum deliveries are contraindicated at less than 34 weeks.

Vaginal breech delivery

Despite clear guidelines on vaginal breech delivery and its contraindications, there is no guideline on vaginal delivery of the preterm breech. RANZCOG and RCOG advise considering vaginal delivery only if the breech is in frank or complete position and that the woman birth in lithotomy with an epidural.3 4 Spontaneous expulsion is preferable to breech extraction, with the use of specific manoeuvres, such as Lovsetts for the arms and Mauriceau-Smellie-Viet or Burns Marshall technique for delivery of the aftercoming head, if required.

There is a theoretical risk of entrapment of the aftercoming preterm breech head in a partially dilated cervix, due to the larger head-to-abdominal circumference ratio compared to that of a term or near-term fetus. Uterine relaxation with a beta-adrenergic agonist or nitroglycerin can be attempted, with the use of manoeuvres, for example, Durhssen’s incisions, symphysiotomy and Zavanelli manoeuvre with caesarean delivery, as the last resort due to their potential fetal and maternal risks.

Excessive handling of the breech during such manoeuvres can result in trauma and injury. Ways to minimise this include avoidance of pulling on the baby, use of a gauze pack on the torso and abdomen, holding the breech by the legs and delivery en caul if possible.

Classical caesarean section

The decision for a classical incision on the uterus may be made due to the position of the fetus, multiple gestations, placental location and an absent lower segment. Other incisions, such as an upper transverse, can also be considered. Although a classical incision is more invasive than a lower segment, it is definitely preferable to a J or a T incision.

A large classical incision can facilitate an atraumatic delivery of the fetus, especially if delivery can be achieved en caul. Inserting your whole hand into the uterine cavity to carefully turn babies into a deliverable position or performing a breech extraction is also easier with good access. Such access can aid a speedy delivery of the fetus and avoid hypoxia.

Evidence-based practice

There is currently a lack of strong evidence to suggest the benefits of one mode of delivery of the preterm infant over the other.5 One large retrospective cohort study failed to identify a statistical benefit of caesarean over vaginal delivery of a preterm fetus, in terms of development of retinopathy, necrotising enterocolitis, respiratory distress syndrome, grade III–IV intraventricular haemorrhage and neonatal death.6 As for maternal outcome, one retrospective cohort study found no difference in the incidence of postpartum haemorrhage, blood transfusion, operative and postpartum complications and chorioamnionitis, in either modes of preterm delivery between 23 to 34 weeks.7 8

Useful tips

As life is a succession of lessons, which must be lived to be understood, and the road of excess leads to the palace of wisdom, here are some words of wisdom from two experienced obstetricians from the sole tertiary obstetrics hospital in Western Australia.

  • Dr Anne Karczub MBBS FRANZCOG, Consultant Obstetrician
  • Dr Scott White MBBS PhD FRANZCOG CMFM, Consultant Obstetrician MFM Service.

What is your approach to interpretation of the preterm intrapartum CTG; what factor influences you to intervene?

Dr Karczub: I’m not looking for reactivity, I’m not necessarily looking for sustained accelerations. I’m looking for variability and the absence of sinister features. The point with the preterm fetus is that you’ve got a lower threshold for intervening soon because of the concern that you’ve got a fetus
with less reserve, so you wouldn’t watch something as long.

Dr White: They are less likely to be reactive, often have shorter accelerations and have accelerations of lower magnitude. They have often somewhat reduced variability, some of those are due to prematurity, some of those due to the drugs we give, such as magnesium sulphate or analgesics, that impact on the fetal heart rate. Ultimately, you interpret the preterm intrapartum CTG as you would a term CTG, the principles are the same. I guess the issue is having, before this woman is in labour, a plan for what you are and aren’t going to act upon.

What is your top tip for the obstetrician at a preterm vaginal delivery?

Dr Karczub: Have a paediatrician present. Second top tip is to prepare yourself for the unexpected. At the very severe preterm, fetuses can turn themselves around as they are coming down the canal. So, with a woman pushing, you can get a baby that at 24 or 26 weeks was cephalic, but becomes a malpresentation, especially a shoulder presentation, as they can banana inside the birth canal.

Beware the preterm head, because the preterm head is that much bigger than the preterm body, so that when the cephalic presentation comes to the perineum, they can distend and distend and then the baby fly out like a champagne cork. Beware the champagne cork phenomenon.

Dr White: Expect the unexpected. Often, they’ll present in unusual ways, shoulders, brows and faces. Also, you can deliver vaginally some presentations in extremely preterm gestations that you can’t do at term.

Table 1. Specific complications of instrumental deliveries in preterm gestations.

Potential risks Prevention
Vacuum Intraventricular haemorrhage
Cephalohaematoma
Subgaleal haemorrhage
Tissue and skin trauma/lacerations
Neck injury
Vacuum delivery contraindicated at <34 weeks
Forceps Skull fracture
Skin lacerations
Facial injury
Neck injury
Bruising
Forceps slipping off the fetal head
Forceps relatively contraindicated at <34 weeks,
use with caution
Do not attempt rotational forceps in the preterm infant
Only apply an instrument if certain of fetal position
Use ultrasound intrapartum to assess fetal head position
Use guided pushing and lithotomy position

 

What is your top tip for the obstetrician at a preterm caesarean delivery?

Dr Karczub: Be brave and do not be afraid to do a classical if that is what is needed to deliver the baby. Do not be tempted by a poorly formed lower segment that is not going to allow adequate lower segment incision to deliver the baby. With a classical incision, the body of the uterus is very thick, so you just have to be brave and have confidence that you are going to get there eventually. The trick is to open the full incision on the uterus, don’t have a very small incision going down and down into a deep dark hole that’s welling blood. Make a big incision. Once you’re in, you can still extend with scissors, be brave.

Dr White: Always have a plan B, and probably a plan C and a plan D. These babies can be extremely difficult to deliver, you’ve got limited access to get your hand in to manipulate this fetus, all the while wanting to do it very gently. Having a thought in your mind as to what steps you’ll take if you encounter difficulty is important. These are things like tocolysis, and making J or T incisions. Give yourself plenty of room: big baby, big hole; small baby, big hole.

With a preterm in breech position, what is the main factor that influences your decision for an attempt at vaginal delivery or caesarean section?

Dr Karczub: If fully dilated, the body of the preterm fetus is in the vagina (not just the feet in the vagina and the buttocks at or above the pelvic brim), then one would generally be considering a vaginal delivery. If the breech is on the pelvic floor, one does a vaginal delivery, with good analgesia, long scissors and Jackson’s and Sim’s retractors in the room, and being mentally prepared to incise the cervix if it traps the head. Have your instruments for cervical incision there, always. Have someone able to assist. Footling breech with high buttocks is at risk of cord prolapse with an incompletely dilated cervix. If the cervix is not fully dilated, asses as you would for any planned vaginal breech with consultation and counselling with the parents. Is the baby going to withstand vaginal birth? Keep membranes intact for as long as possible, as it buffers the baby against injury. Finally, always do the vaginal examinations yourself! People get the vaginal exams wrong in these circumstances.

Dr White: Several things; parental wishes are paramount. What they want. They should know that there is some evidence to suggest that for extremely preterm breech babies, you shouldn’t be averse to doing a caesarean section if it’s indicated. Another thing is obstetric experience. Given the low rate of breech vaginal births in contemporary practice, it may be that the obstetrician is more comfortable doing a caesarean section than a vaginal breech delivery. For the preterm breech, do continuous electronic fetal monitoring, have another experienced obstetrician or senior midwife with you, try and leave the membranes intact as you are less likely to get head entrapment, don’t pull on it. Be gentle with your manoeuvres as membranes are very easy to break. Have available a Jackson’s retractor and a pair of long scissors so you are prepared to do a cervical incision quickly if required.

Table 2. Management of head entrapment during vaginal breech delivery. .

Manouvres Description Risks
McRoberts position Flexion of maternal knees so that the anterior aspect of the thighs are pressed against the abdomen
Uterine relaxation Beta adrenergic agonist (terbutaline 250 μg subcutaneous)
Nitroglycerin
General anaesthesia
Maternal tachycardia
Uterine atony
Duhrssen’s incision 1–2 fingers placed between the partially dilated cervix and the presenting part, with incisions made along the length of the undilated cervix at 6, 2 and 10 o’clock Extension of incision to the lower uterine segment or broad ligament
Injury to uterine vessels, ureter and bladder
Severe haemorrhage
Cervical incompetence in subsequent pregnancy
Symphysiotomy Infiltration of the symphysis pubis and overlying skin with local anaesthesia
Insertion of firm catheter into the urethra to displace it laterally
Incision made over the symphysis to separate it just enough to deliver the head
Pelvic instability, requiring delayed orthopaedic repair
Zavanelli manoeuvre and caesarean delivery Administration of tocolytic and attempt to replace the fetal body into the uterus, followed by caesarean section Complications of caesarean section
Cervical injury and subsequent cervical incompetence

 

In the setting of a cephalic presentation labour at less than 34 weeks, where the cervix is fully dilated but the vertex is not advancing, what do you advise if you need to expedite delivery?

Dr Karczub: If you need to put an instrument on, then you do. You just have to be really careful that when you pull, you pull gently as you can with the forceps over the baby’s head. I’ve seen quite bad trauma, like ripping off babies’ ears and so forth. I have one time only, in the context of a second twin that was vertex and high and was basically at the pelvic brim, just put my whole hand in and grabbed the baby by the head and manually pulled the baby out. I have also done that in the setting of when babies banana inside the vagina, put my whole hand in and pulled the baby out. It’s that group, too, that the forceps don’t fit that well. With your hand you are probably doing less damage than forceps.

Dr White: I wouldn’t do a vacuum extraction of a preterm baby, but I would use forceps. I think it’s very reasonable if there is an indication to expedite delivery, even in a preterm fetus, to use forceps. You usually don’t need to at extremely preterm gestations. But it’s certainly not impossible, you are better off to do a straightforward gentle forceps delivery than to have an asphyxiated preterm baby.

You’re performing a severely preterm caesarean section in the back down transverse position, please discuss your approach to delivery.

Dr Karczub: If you’re having difficulty or have done a lower segment, for example, and the uterus is clamping down, do the usual things. Try to get uterine relaxation, glyceryl trinitrate (GTN), get your whole hand in and cradle the baby, try to bring the head around or bring the breech around. With your whole hand or arm inside the uterus, bring that baby around in a somersaulting position. Usually the head first. The breech is difficult as you’ve got to go through a longer rotation. Do what feels to be the right thing at the time. Make a big incision and don’t be afraid to do a T if you don’t have a classical.

Dr White: For a preterm transverse fetus, even if the lower segment seems appropriately formed, you should always think, ‘should I be making a classical incision?’ It enables your plan B, in that you have the access that you need to manipulate that fetus. Other things are having an experienced assistant, an experienced anaesthetist and having access to tocolysis, such as GTN. Try to find a foot. Also think about scanning the patient immediately before starting, so you know where the legs are, which way to rotate the fetus, and where the placenta is.

Conclusion

Early preterm delivery is often a daunting experience for both the medical team and the patient. The field of obstetrics is fraught with known knowns, known unknowns and unknown unknowns. Hence, preparation and anticipation of potential complications is the key to a safe delivery of a preterm infant.

References

  1. Jennings B, Joyce A, Pierce A. Western Australia’s Mothers and Babies, 2014: 32nd Annual Report of the Western Australian Midwives’ Notification System. Government of Western Australia, Department of Health; 2018. (105).
  2. March of Dimes, PMNCH, Save the Children, WHO. Born Too Soon: The Global Action Report on Preterm Birth. Eds CP Howson, MV Kinney, JE Lawn. Geneva: World Health Organization; 2012.
  3. RANZCOG Women’s Health Committee. Management of breech presentation at term. RANZCOG; 2016.
  4. Impey L, Murphy D, Griffiths M, Penna L. Management of Breech Presentation: Green-top Guideline No. 20b. BJOG Int J Obstet Gynaecol. 2017;124(7):e151-77.
  5. Mercer BM. Mode of delivery for periviable birth. Semin Perinatol. 2013;37(6):417-21.
  6. Racusin DA, Antony KM, Haase J, et al. Mode of Delivery in Premature Neonates: Does It Matter? AJP Rep. 2016;6(3):e251-9.
  7. Kuper SG, Sievert RA, Steele R, et al. Maternal and Neonatal Outcomes in Indicated Preterm Births Based on the Intended Mode of Delivery. Obstet Gynecol. 2017;130(5):1143-51.
  8. Lin C-H, Lin S-Y, Yang Y-H, et al. Extremely Preterm Cesarean Delivery ‘En Caul.’ Taiwan J Obstet Gynecol. 2010;49(3):254-9.

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