I’m enjoying some down time at present and decided to use it to catch up on a backlog of reading. Here are some of the papers that caught my eye recently.
Post-term pregnancy and the incidence of complications – a national study from Denmark.
Andersson and colleagues (2021) used routinely collected birth statistics and compared outcomes for babies and women who planned to give birth vaginally, and who had singleton pregnancies. They compared births occurring between 41 weeks to 41 weeks and 3 days (79,160 births), with 41 weeks and 4 days to 42 weeks (55,717 births).
Stillbirth and neonatal death rates were low, and occurred at the same rate in both gestational age cohorts (stillbirth 6 per 10,000 births at 41+0 – 41+3 weeks vs 5 per 10,000 births at 41+4 – 42 weeks; neonatal death 3 per 10,000 births at 41+0 – 41+3 weeks vs 4 per 10,000 births at 41+4 – 42 weeks). There was an increase in meconium aspiration and low Apgar scores at the later gestation but the absolute risks for any complication for the baby remained low during the 41st week. The authors generated a composite perinatal outcome (adding up 14 possible complications), and this occurred in 17 per 10,000 births at 41+0 – 41+3 weeks vs 27 per 10,000 births at 41+4 – 42 weeks. This was a statistically significant increase (once corrected for known confounders like induction of labour).
For women, increasing gestational age was associated with an increased chance of caesarean section (110 per 1000 vs 153 per 1000), instrumental vaginal birth (92 per 1000 vs 113 per 1000), shoulder dystocia (14 per 1000 vs 15 per 1000), postpartum haemorrhage (40 per 1000 vs 52 per 1000 for 1000 – 1500 mL blood loss; and 19 per 1000 vs 23 per 1000 for > 1500 mL blood loss), and severe perineal trauma (35 per 1000 vs 45 per 1000).
I find that research such as this is useful in providing concrete figures to help in counselling. It is easy to fall into the trap of thinking that perinatal deaths are common after term (I was once asked to provide a second opinion for a woman who had been incorrectly counselled that one in two babies die in pregnancies that progress beyond 41 weeks). It is reassuring to be reminded that perinatal mortality rates remain low throughout the 41st week of pregnancy.
Colour coded CTG interpretation tools: do they improve outcomes?
The health department in Queensland, Australia adopted the use of a colour coded tool to assist in the interpretation of intrapartum CTG data several years ago. Willis et al (2021) report on retrospective data from one busy maternity hospital in Queensland, comparing outcomes for a period prior to the introduction of the tool with a period after. They found no change in perinatal outcome or use of caesarean section, but an increase in the rate of spontaneous vaginal birth, and a fall in the use of instrumental vaginal birth.
It is important that we assess the effectiveness of wide scale changes to healthcare policy, such as this. It is reassuring to see that it appears to have been protective for vaginal birth, while being disappointing that it hasn’t improved perinatal outcomes (which is after all the goal of fetal monitoring).
Anaemia in women and the incidence of abnormal CTG patterns
Beerman, et al. (2022) have published the abstract from their recent conference presentation. They identified a population of women in labour with a haemoglobin concentration of under 11 g/dL at admission to hospital and compared this to women with a haemoglobin concentration of > 11 g/dL. All women had continuous intrapartum CTG monitoring. Women with anaemia were found to be less likely to have an abnormal CTG trace in the hour prior to birth.
They didn’t report on whether this translated into different outcomes for babies. This brief abstract raises lots of interesting questions and will hopefully be followed by further research to confirm and extend on these findings. Understanding what is happening with the physiology may reveal useful insights. It is worth noting that there may be a downside to aggressively managing mild anaemia in pregnancy.
Bias and CTG interpretation: Obesity and race impact on the decision for surgical birth
The final thing to catch my eye was a conference poster from Huysmann, et al. (2022). Their study population was made up of women with an abnormal intrapartum CTG trace. The rate of use of caesarean section and instrumental vaginal birth for women with the same category of CTG abnormality were compared between women who were obese and those who were not, and this was further stratified by race. Obese women were more likely to experience surgical birth than non-obese women. The rate of caesarean section was also higher among black women, both in the obese and non-obese groups.
This study is a good reminder that CTG interpretation is subjective and that personal, cultural, and institutional biases impact on the decisions we make in relation to fetal monitoring. These are difficult to see in daily life, becoming visible only when we look for patterns in larger data sets.
References
Andersson, C.B., Peterson, J.P., Johnsen, S.P., Jensen, M., & Kesmodel, U.S. (2021). Risk of complications in the late versus early days of the 42nd week of pregnancy: A nationwide cohort. Acta Obstetrica Gynecologica Scandanavica, 00, 1–12. https://obgyn.onlinelibrary.wiley.com/doi/pdfdirect/10.1111/aogs.14299
Beerman, S.E., Watkins, V.Y., Frolova, A.I., Raghuraman, N., & Cahill, A.G. (2022). Electronic fetal monitoring changes in the setting of maternal anemia. American Journal of Obstetrics and Gynecology, 226(1, supplement), S83. https://www.ajog.org/article/S0002-9378(21)01351-X/fulltext
Huysmann, B.C., Odibo, A.O., Carter, E.B., Kelly, J.C., Frolova, A.I., Cahill, A.G., & Raghuraman, N., (2022). Making the diagnosis of non-reassuring fetal status: Potential for implicit bias. American Journal of Obstetrics and Gynecology, 226(1, supplement), S353. https://www.ajog.org/article/S0002-9378(21)01791-9/fulltext
Willis, M., Dunn, L., Okano, S., Janssens, S., & Kumar, S. (2021). The impact on obstetric and perinatal outcomes in term infants following the introduction of a colour-coded, hierarchical cardiotocography classification system: A retrospective non-inferiority study. Australian and New Zealand Journal of Obstetrics and Gynaecology, in press. https://obgyn.onlinelibrary.wiley.com/doi/abs/10.1111/ajo.13469
- New horizons for fetal monitoring: Photoacoustic assessment of the fetal brain and placenta
- What’s the deal with early decelerations and head compression?
Categories: CTG, EFM, New research, Perinatal mortality, Stillbirth
Tags: anaemia, bias, caesarean section, instrumental birth, obesity, Perineal trauma, post term, postpartum haemorrhage, race, Stillbirth
Birth Small Talk 
Thanks for this run down. Such interesting research. I find the research on anaemia particularly interesting. We work so hard during pregnancy to prevent what we consider to be anaemia. Perhaps one day our parameters will change.
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It’s a great reminder that there is still an awful lot of basic physiology we don’t fully understand about pregnancy.
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