Home Medizin Fettleibigkeit bei Müttern und Fettleibigkeit in Kombination mit anderen Risikofaktoren sind mit einem erhöhten Totgeburtsrisiko verbunden

Fettleibigkeit bei Müttern und Fettleibigkeit in Kombination mit anderen Risikofaktoren sind mit einem erhöhten Totgeburtsrisiko verbunden

von NFI Redaktion

Past research suggests that the risk of stillbirth in women with obesity increases by two to five times. However, the impact of different levels of obesity severity on live births outcomes is not well understood.


Study: The impact of isolated obesity compared to obesity and other risk factors on the risk of stillbirth: a retrospective cohort study. Image credit: FotoDuets/Shutterstock.com










Study: The impact of isolated obesity compared to obesity and other risk factors on the risk of stillbirth: a retrospective cohort study. Image credit: FotoDuets/Shutterstock.com

A recent study in CMAJ compared the risk of stillbirth in obese mothers in two categories. One category included only obesity as a risk factor, while the other category had unidentified or additional high-risk factors affecting the pregnancy.

Introduction

Factors such as pre-existing diabetes or hypertension interact with obesity and increase the risk of pregnancy complications. These conditions are also more common in obese mothers. Pregnancy complications like gestational hypertension, gestational diabetes, or fetal growth restriction are also more frequent in obese women and are associated with an increased stillbirth rate.

A better understanding of how these factors interact is necessary to provide appropriate counseling to women with such risk factors, both in terms of early pregnancy care and the best timing for delivery.

The data was sourced from the Better Outcomes Registry and Network (BORN), Ontario, and only included singleton births in hospitals. The study period ranged from 2012 to 2018. The aim was to assess how body mass index (BMI) directly and indirectly affects the risk of stillbirth after compensating for other contributing factors and independent risk factors.

What Did the Study Find?

The study included approximately 680,000 births, with nearly 2,000 stillbirths among them.

Stillbirths were more common in individuals with obesity. However, they were also more prevalent in individuals who had not given birth before, those using assisted reproduction techniques, and those with lower family income. Furthermore, those who consumed substances or smoked, as well as those with pre-existing conditions including hypertension and diabetes, were at higher risk.

Obesity was more frequent in women with more children, lower financial status, and in women who smoked. Both obesity classes I and II were more strongly associated with pre-delivery stillbirths compared to women with normal BMI. Obesity classes II and III had a higher likelihood of stillborn infants, and also experienced gestational hypertension and diabetes.

Compared to the overall pregnant population of the country, there were also elevated rates of stillbirths, congenital anomalies, and growth-restricted fetuses.

Overall, the risk of stillbirth significantly increased with obesity after compensating for some or all confounding factors identified in this study. The risk also increased with gestational age.

Obesity class I was associated with a 56% higher probability of stillbirth after the 37th week of pregnancy compared to individuals with normal BMI. However, the strongest connection was seen with obesity classes II, where the likelihood more than doubled, and with obesity class III where the probability increased by 80%.

Therefore, obesity with or without other risk factors at the time of delivery was significantly associated with an increased likelihood of stillbirth at delivery or beyond, compared to pregnancies in non-obese women. The risk increases with gestational age, peaking at the time of delivery (37 completed weeks of pregnancy).

The increased risk with obesity class I was only observed in the 39th week, where it was double that of women with normal BMI. Obesity classes II and III showed higher risks after 38 and 40 weeks compared to women with normal BMI. Obesity class II peaked again after 41 weeks.

Higher risks were observed in women with obesity classes II or III after 38 weeks, namely 3.5 and 2.6 times higher, respectively, than women with normal BMI. However, stillbirth rates increased even further at 40 weeks. The lower risks at 37 and 39 weeks may be attributed to smaller sample sizes in these age groups.

For women with pre-existing hypertension or diabetes, the risk doubled after 38 weeks but decreased thereafter. This could be due to standard recommendations ensuring most women with these conditions deliver at this gestational age.

Only about 70% and 10% of the risk could be explained by preterm births and hypertensive disorders in the obesity cohort after accounting for all potential confounding factors. This does not indicate a definitive role of these conditions in mediating the association of obesity with stillbirths. In contrast, the likelihood of stillbirth in small-for-gestational-age (SGA) infants was lower, possibly because they were monitored more closely.

The study supports previous observations that obesity, especially in higher classes, increases the risk of stillbirth in women and increases with gestational age even when considering other potentially undiagnosed factors.

What Are the Implications?

Previous studies using the same data suggested that the risk of preeclampsia and other maternal and fetal complications at delivery could be reduced by delivering at this gestational age, supporting these recommendations. In fact, another study from 2014 found that 200 stillbirths could be avoided if women with obesity gave birth at 38 weeks instead of waiting until 41 weeks. This confirms the conclusion for higher obesity classes.

Our results suggest that giving birth around the 39th week of pregnancy for women with obesity class I and around the 38th week for women with obesity classes II or III may help reduce the risk of stillbirth.

Journal Reference:

  • Ramji, N. Corsi, DJ, Dimanlig-Cruz, S. et al. (2024). The impact of isolated obesity compared to obesity and other risk factors on the risk of stillbirth: a retrospective cohort study. CMAJ. doi: https://doi.org/10.1503/cmaj.221450

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