Jennifer (not real name) booked with me for management of her first pregnancy. She and her husband are a delightful couple, and they were very excited about having a baby. Jennifer was planning to have vaginal delivery.

Her baby measured about 1 week larger than her LMP dates on ultrasound measurement at her first two antenatal visits at 10 weeks and 14 weeks gestation by LMP dates. So, I revised her EDC forward. There after her revised EDC was used to calculate gestation.

Her baby at the next four antenatal visit measured 1 to 2 weeks larger than the revised EDC on ultrasound scan measurement. When she was 35 weeks 6 days by revised EDC her baby was measuring 3871gms by my ultrasound scan estimate. I arranged for an ultrasound check at a specialised pregnancy ultrasound unit because of their extra training and expertise in pregnancy ultrasounds. They estimated the baby had a weight of 3902gms which was >99th centile. At her next antenatal visit (37 weeks 1 day) I estimated by ultrasound measurements her baby’s weight to be 4427gms and at the following week antenatal visit (38 weeks 1 day) to be 4978gms. She did not have gestational diabetes.

We had been discussing the labour and delivery concerns and delivery options with her baby being very large since the independent ultrasound scan result was known.

The risks of a baby being very large when a woman is planning to have a vaginal delivery are:
1. Obstructed labour. This is where the baby is too big for the pelvis. If there is lack of progress in first stage labour a Caesarean section is indicated. If there is lack of progress (descent of baby’s head) in second stage labour despite a mother’s best pushing efforts, then a Caesarean section may be needed. This is a more challenging and risky Caesarean section for the mother as baby’s head is usually wedged in the pelvis. Otherwise, there would be an operative vaginal delivery (vacuum cup or forceps). There needs to be careful assessment of the likelihood of the operative vaginal delivery working and informed consent. And even if it looks likely an operative vaginal delivery should be safe and successful it should be attempted carefully with the knowledge that the delivery mode may need to be converted to a Caesarean section.

2. Baby incuring brain damage and other trauma because of childbirth  While I personally have never had an issue, I do know cases of other obstetricians where an operative vaginal delivery has caused permanent damage to the baby. Experience is very important and a trainee obstetrician, or junior obstetrician or poorly trained obstetrician may not have the necessary expertise and so there is greater risk if such a doctor is delivering yor baby.

3. Shoulder dystocia Even if the mother can deliver the baby’s head with pushing or there has been a successful vacuum or forceps delivery of baby’s head, there can still be a challenge in delivering baby’s shoulders. This is called shoulder dystocia. Once baby’s head is out, there is less or no oxygen getting to baby, because the umbilical cord is squashed and the baby’s lungs are compressed in the mother’s pelvis. There is great urgency in delivering baby. It is too late for Caesarean section. There are various manoeuvres that an experienced obstetrician knows and can perform than can overcome a shoulder dystocia issue. But occasionally there can be consequential breaking of baby’s clavicle (which will heal) and sometimes stretching of the brachial plexus of nerves that supply baby’s arm. If this is mild there will be full recovery and if severe there can be permanent paralysis of the arm (called Erb’s palsy). When I was an obstetric resident I witnessed a senior obstetric registrar being unable to deliver a baby because of shoulder dystocia and the baby dying with only its head delivered. I was told of a fully qualified obstetrician who had the same outcome because he could not deliver the baby’s shoulders.

4. Maternal trauma. With a more challenging operative vaginal delivery there is increased risk of significant maternal trauma. There is a greater incidence of nasty vaginal tearing, third degree perineal tearing and fourth degree perineal tearing. While an episiotomy is usually due to minimise the risk of perineal tearing there can still be significant tearing. Major tearing results in lots of suturing, more perineal discomfort than usual and if the repair is not no done correctly and sometimes even if it is done correctly ongoing issues such faecal incontinence (if tearing involves the anal sphincter) and dyspareunia (painful sexual intercourse).

There were options I put to Jennifer:
• To do nothing and hope for the best.
• Early induction of labour to avoid the baby getting larger.
• Elective Caesarean section.

When I saw Jennifer at her anetnatal visit after her independent ultrasound scan, when she was 37 weeks 1 day gestation, I estimated her baby’s weight by ultrasound scan measurements to now be 4427gms. While ultrasound scan estimates are only approximate, with the consistency ultrasound scan estimates of her baby being large on measurements andwith her baby feeling to be large on abdominal palpation, it was most likely this was the case. There also was the possibility the ultrasound scans may have underestimated the baby’s weight.

To do nothing was not good idea as this would most likely result in the baby being over 5kg before it was born.

Induction of labour was most likely not the best option. Many women have challenges in easily delivering a 4.0Kg baby let alone a 4.5Kg plus baby. So we decided against induction. I advised her my preference was an elective Caesarean section delivery.

A Caesarean section avoided all the potential risks of vaginal delivery for both mother and baby. While there were surgical risks, they were not as great a vaginal delivery risks. The downside, which I pointed out to her, was we may have overestimated baby’s size and if the baby was significantly smaller Jennifer would be then left wondering: “Did I have a Caesarean section unnecessarily?”

At Jennifer’s next antenatal visit when she was 38 weeks 1day gestation I estimated by ultrasound measurements her baby’s weight to be 4978gms. Jennifer agreed to having Caesarean section, as it was the safest option. She was upset as she was planning to have vaginal delivery. But she trusted me and my recommendation.

The elective Caesarean section was done the next week when she was 39 weeks gestation. It was done under a spinal anaesthetic and was uncomplicated. Her daughter was born in excellent condition and had a birth weight of 4775gms. The Caesarean section was “baby friendly”, which meant she was able to hold her baby after delivery, while I was completing the operation and she, baby and her husband went to recovery ward and then back to the ward together. Her postnatal course was uneventful. Baby did well also.

When I saw Jennifer for her 6-week postnatal visit in my rooms, she was doing well and had no issues. Her daughter was also doing well. We again discussed the decision to have Caesarean section. She was very pleased that she had agreed to having an elective Caesarean section, with consideration of her baby’s generous birth weight. While the baby weighed at birth 203gms less than I estimated at my last ultrasound scanning, baby had a very generous at 4775gms and baby’s size would most likely not have been compatible with an uncomplicated labour and vaginal delivery. The variation from my scan estimate was about 4%. This is a very acceptable variation for ultrasound scan estimations. Ultrasound scans are always only approximate.

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