Short term thinking is a problem in maternity care. It seems to me as though a good five minute Apgar score, or normal cord blood gases, is the primary end point in far too many studies. These things are not inappropriate outcomes to aim for, but they aren’t enough and can end up meaning professionals in clinical practice lose sight of the big picture. As a parent and birthing woman, I wanted more than for my baby to for them to simply have an Apgar score over seven when they were five minutes old.
A recently published study serves as a good reminder to think big and long term, when we are conducting research, or making recommendations for clinical care. Al Khalaf and colleagues (2024) used a large data base of births (the Swedish Medical Birth Registry) to investigate the risk of stillbirth in the NEXT pregnancy when the first ended with caesarean birth. They also considered whether the risk of stillbirth in the next pregnancy was different depending on whether that birth was a vaginal birth or another caesarean section.
How was the research done?
Information about births occurring between 1982 and 2012 were taken from routinely collected birth data held in the Swedish Medical Birth Registry. To be included, women had to have a given birth for the first time and for a second time, during this period. Women with multiple pregnancies were excluded* as were women who had a stillbirth in their first pregnancy. Information about how the two babies were born was collected, as was information about stillbirth. Death during the antenatal period and during labour was included, and they reported separately on antenatal stillbirth rates and deaths during labour. They also collected information about the cause of death and any medical conditions the women had.
What did they find?
In total, the researchers identified 885,850 women who met the criteria. 2,428 (or 2.7 per 1,000) women had a stillbirth in their second pregnancy, and 136 of these happened in labour (6 in 100 of the stillbirths, or 0.15 per 1,000 of all women). Risk factors for stillbirth in the second pregnancy were:
- being older
- being a smoker
- having a higher BMI
- having chronic hypertension or diabetes
- giving birth at a lower gestational age.
The most common cause of death was fetal growth restriction (21% of stillbirths). The next most common were placental abruption (5%), intrapartum asphyxia (low oxygen in labour – 4%), and congenital abnormalities (3%). Deaths related to uterine rupture were rare (13 in total, 0.5% of stillbirths).
In the first pregnancy, 13% of women gave birth by caesarean section (117,114 women). Of these women, 54% gave birth by caesarean section in the next pregnancy. Women who had vaginal births (this includes instrument assisted vaginal births like vacuum and forceps) in the first pregnancy, had a caesarean section rate of 5% in the next pregnancy.
Women who had any caesarean birth (prior to or during labour) in the first pregnancy (compared to any type of vaginal birth) were more likely to experience stillbirth in the second pregnancy (aOR 1.37, 95% confident interval 1.23 – 1.52 – after adjusting for confounding variables). That’s a statistically significant 37% increase in the stillbirth rate for those not used to reading research maths. This was true for both stillbirth prior to labour (aOR 1.35, 95% confidence intervals 1.21 – 1.51) and during labour (aOR 1.67, 95% confidence intervals 1.09 – 2.53). The overall stillbirth rate was higher both for women who had a pre labour caesarean section in the first birth (aOR 1.31, 95% confidence intervals 1.09 – 1.58) and those who had an in-labour caesarean section (aOR 1.36, 95% confidence intervals 1.19 – 1.55). Instrumental birth in the first pregnancy was not associated with a higher stillbirth rate in the next pregnancy.
There are some folks out there who might be thinking – well that’s all those dangerous vaginal births after caesarean section (VBACs)! There was not even a hint of a relationship between successful VBAC and stillbirth in labour (aOR 0.99, 95% confidence interval 0.48 – 2.06), and this was the same whether the first caesarean was done before or during labour. There was however a higher rate of stillbirth, both in labour and before it, for women who gave birth by caesarean section during labour in the second pregnancy (aOR for antenatal stillbirth 3.67, aOR for in labour stillbirth 5.86). The challenge here is that the authors didn’t analyse outcomes according to women’s intention to have a VBAC in their second pregnancy, only whether they actually gave birth vaginally. They also don’t give information about whether the caesarean section was done because the stillbirth had already occurred. This makes it difficult to use their findings to help weigh up the pros and cons to support decision making about VBAC vs repeat caesarean section.
The final piece of interesting information from the study was the population attributable fraction. In other words – what percent of ALL stillbirths are associated with caesarean section in the first birth? The number was 5%. So, if some magical approach were able to reduce the caesarean section rate for women having their first birth to zero, then the overall stillbirth rate would drop by 5%.
So what does all this mean?
The findings from this research are similar to those published by other research groups previously. They serve as a reminder that caesarean sections have far reaching consequences and are best reserved for situations where there is evidence of clear benefit. For women using the findings of this research to support their own decision making, I would issue the reminder that these results only apply to women in the same situation as those in the study. If you had a vaginal birth, then a caesarean, this study doesn’t relate to you.
Some of you might be thinking – I came here for stuff about CTGs. What does this have to do with that? Well my friend, here’s the thing. Using CTG monitoring increases the use of caesarean section. So, this research lends weight to the argument that using CTG monitoring in pregnancy in a first labour might increase the chance of stillbirth in the second pregnancy.
Good research about CTG monitoring looks at whether CTGs (rather than intermittent auscultation) are associated with a lower rate of stillbirth in the current pregnancy (it isn’t). Really great research would look at whether CTG use in the first pregnancy is associated with a different rate of stillbirth across all the births that woman has during her reproductive lifetime. That research has never been done. So we simply do not know whether there are longer term harms or benefits from CTG use in the first pregnancy. If this information existed, I think women would find it really useful to help them make good decisions about which fetal monitoring approach to use in labour.
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References
Al Khalaf, S. Y., Heazell, A. E. P., Kublickas, M., Kublickiene, K., & Khashan, A. S. (2024, Jan 29). Risk of stillbirth after a previous caesarean delivery: A Swedish nationwide cohort study. BJOG, 1-8. https://doi.org/10.1111/1471-0528.17760
* I do wish researchers would consider including women with multiple pregnancies in their cohorts, and do subgroup analyses of this group. It is really difficult to find good evidence to guide practice for women with multiple pregnancy. We can’t assume that what is true for women with one baby on board is the same for women with multiple pregnancies, or that is is different!
- Is more technology the solution to fetal monitoring?
- Maternal heart rate recording to improve outcomes
Categories: CTG, New research, Stillbirth
Tags: caesarean section, Sweden, VBAC
Birth Small Talk 
Excellent read.
Thank you Kirsten
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Thanks Sheryl!
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Your blogs are glorious! I’m always sharing them. This one IS GOLD!
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Thanks Kemi!
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Asking the right questions.
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That’s the plan – to keep asking the right questions!
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hi there
still love your work!
can you please update my email address to bethsaradashorty@gmail.com
the link at the bottom of your email didn’t work for me to manage my
settings
Warmly,
Beth Shorter
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