Prepregnancy body mass index and the length of gestation at term

doi:10.1016/j.ajog.2007.05.048

American Journal of Obstetrics and Gynecology

Volume 197, Issue 4, October 2007, Pages 378.e1-378.e5

Presented at the 27th Annual Clinical Meeting of the Society for Maternal–Fetal Medicine, San Francisco, CA, Feb. 5-10, 2007.

https://doi.org/10.1016/j.ajog.2007.05.048 Get rights and content

Objective

The purpose of this study was to examine the relationship between prepregnancy body mass index (BMI) and length of gestation at term.

Study Design

This was a retrospective study of 9336 births at the University of California, San Francisco, at ≥37 weeks’ gestation. We performed univariate and multivariable analyses of the associations between prepregnancy BMI and length of gestation (≥40, ≥41, and ≥42 weeks’ gestation).

Results

Overweight women were more likely to deliver at ≥40, ≥41, and ≥42 weeks’ gestation than were women who were underweight or normal weight. In multivariable analyses, higher prepregnancy BMI was associated with higher risk of progressing past 40 weeks. Obese women had 69% higher adjusted odds of reaching 42 weeks’ gestation, compared with women of normal prepregnancy BMI (adjusted odds ratio, 1.69; 95% confidence interval, 1.23-2.31).

Conclusion

Higher BMI is associated with prolonged gestation at term. Achieving optimal BMI before conception may reduce the risk of postterm pregnancy and its associated complications.

Section snippets

Materials and Methods

This retrospective cohort was selected from women who delivered singleton infants at the UCSF Medical Center between 1990-2001. The UCSF perinatal division maintains the research database that was used for this study. Demographic, antenatal, intrapartum, and delivery data are entered into a preprinted datasheet by the delivering physician or midwife immediately after every birth, and additional neonatal and discharge data are entered into the database by trained abstractors. For this study, we

Results

The study cohort consisted of 9336 term births; 47.4% of the pregnancies were delivered between 37-39 weeks’ gestation; 47.2% of the pregnancies were delivered at 40-41 weeks’ gestation, and 5.4% of the pregnancies were delivered at ≥42 weeks. Characteristics that were associated with longer gestation at term were white race/ethnicity, lower parity, higher weight gain, and private insurance. Asian women were less likely to progress past 40 weeks’ gestation, compared with other groups (Table 1).

Comment

In this cohort of women who delivered at ≥37 weeks’ gestation, we found that higher prepregnancy BMI was associated with longer gestation at term and higher risk of postterm pregnancy. Not only are overweight and obese women at increased risk of prolonged pregnancy, but underweight women are at a slightly decreased risk, compared with women with a normal prepregnancy BMI.

Our findings are consistent with those of Usha Kiran et al,¹⁰ who found that obese women were more likely to have a postterm

References (24)

M.Y. Divon et al.
Fetal and neonatal mortality in the postterm pregnancy: the impact of gestational age and fetal growth restriction
Am J Obstet Gynecol
(1998)
A.W. Olesen et al.
Perinatal and maternal complications related to postterm delivery: a national register-based study, 1978-1993
Am J Obstet Gynecol
(2003)
V.M. Allen et al.
Economic implications of method of delivery
Am J Obstet Gynecol
(2005)
L. Fonseca et al.
Postdates pregnancy in an indigent population: the financial burden
Am J Obstet Gynecol
(2003)
C.A. Hickey et al.
Low pregravid body mass index as a risk factor for preterm birth: variation by ethnic group
Obstet Gynecol
(1997)
A.B. Caughey et al.
What is the best measure of maternal complications of term pregnancy: ongoing pregnancies or pregnancies delivered?
Am J Obstet Gynecol
(2003)
A.B. Caughey et al.
Neonatal complications of term pregnancy: rates by gestational age increase in a continuous, not threshold, fashion
Am J Obstet Gynecol
(2005)
W.F. Rayburn et al.
Rising rates of labor induction: present concerns and future strategies
Obstet Gynecol
(2002)
L. Sanchez-Ramos et al.
Labor induction versus expectant management for postterm pregnancies: a systematic review with meta-analysis
Obstet Gynecol
(2003)
L. Rand et al.
Post-term induction of labor revisited
Obstet Gynecol
(2000)

I. Ingemarsson et al.

Stillbirths and rate of neonatal deaths in 76,761 postterm pregnancies in Sweden, 1982-1991: a register study

Acta Obstet Gynecol Scand

(1997)

A.B. Caughey et al.

Complications of term pregnancies beyond 37 weeks of gestation

Obstet Gynecol

(2004)

Cited by (96)

Challenges in timing and mode of delivery in morbidly obese women
2024, Best Practice and Research: Clinical Obstetrics and Gynaecology
Globally obesity is increasing especially in the reproductive age group. Pregnant women with obesity have higher complication and intervention rates. They are also at increased risk of stillbirth and intrapartum complications. Although organisations like NICE, RCOG, ACOG and WHO have published guidelines and recommendations on care of pregnant women with obesity the evidence from which Grade A recommendations can be made on timing and how to deliver is limited. The current advice is therefore to have discussions with the woman on risks to help her make an informed decision about timing, place, and mode of delivery.
Obesity is an independent risk factor for pregnancy complications including diabetes, hypertension and macrosomia. In those with these complications, the timing of delivery is often influenced by the severity of the complication. As an independent factor, population based observational studies in obese women have shown an increase in the risk of stillbirth. This risk increases linearly with weight from overweight through to class II obesity, but then rises sharply in those with class III obesity by at least 10-fold beyond 42 weeks when compared to normal weight women. This risk of stillbirth is notably higher in obese women from 34 weeks onwards compared to normal weight women. One modifiable risk factor for stillbirth as shown from various cohorts of pregnant women is prolonged pregnancy. Research has linked obesity to prolonged pregnancy. Although the exact mechanism is yet unknown some have linked this to maternal dysregulation of the hypothalamic pituitary adrenal axis leading to hormonal imbalance delaying parturition. For these women the two dilemmas are when and how best to deliver.
In this review, we examine the evidence and make recommendations on the timing and mode of delivery in women with obesity. For class I obese women there are no differences in outcome with regards to timing and mode of delivery when compared to lean weight women. However, for class II and III obesity, planned induction or caesarean sections may be associated with a lower perinatal morbidity and mortality although this may be associated with an increased in maternal morbidity especially in class III obesity. Studies have shown that delivery by 39 weeks is associated with lower perinatal mortality compared to delivering after in these women. On balance the evidence would favour planned delivery (induction or caesarean section) before 40 weeks of gestation. In the morbidly obese, apart from the standard lower transverse skin incision for CS, there is evidence that a supraumbilical transverse incision may reduce morbidity but is less cosmetic. Irrespective of the option adopted, it is important to discuss the pros and cons of each.
Intrapartum care and management of complications in women with obesity
2023, Best Practice and Research: Clinical Obstetrics and Gynaecology
Pregnant women with obesity are at considerable risk during their labor and delivery. The aim of obstetric care is the safe delivery of the baby and the maintenance of good health of the mother while providing an ongoing support for the family unit. The awareness and mitigation of risks associated with caring for women who are obese is vital in ensuring continued good outcomes. Transfer of women for labor care, presence of senior staff, bariatric resources, understanding of the progress of labor with an increase in body mass index, and preparation for complications are covered in this chapter.
Impact of maternal pre-pregnancy body mass index on maternal, fetal and neonatal adverse outcomes in the worldwide populations: A systematic review and meta-analysis
2021, Obesity Research and Clinical Practice
Citation Excerpt :
308 full texts were reviewed, and 222 studies were excluded (Fig. 1). Finally, 86 [5,8–23,25–27,46–111] articles describing 20,328,777 pregnancies (range: 380–7,141,630) were included in this systematic review and meta-analysis. The characteristics of the 86 [5,8–23,25–27,46–111] included studies were presented in Tables S2–S3.
Systematic review and meta-analysis conducted to investigate the effect of stratified pre-pregnancy maternal body mass index on twenty maternal and fetal/neonatal adverse outcomes.
PubMed, Google Scholar, Medline, Embase, Web of Science databases were searched from inception till July 11, 2020. Cohort studies were included. The pooled odds ratio with 95% confidence interval was reported considering the random effect and the quality effect model. The sub-group analysis and meta-regression were conducted for BMI cut-offs, geographical region, source of BMI, and sample size.
Overall, 86 studies representing 20,328,777 pregnant women were included in this meta-analysis. Our study reveals that overweight and obese mothers are at increased odds of cesarean delivery, elective cesarean delivery, emergency cesarean delivery, gestational diabetes, gestational hypertension, induction of labor, postpartum hemorrhage, pre-eclampsia, pre-term premature rupture of membrane, and the fetuses/neonates of overweight and obese mothers are at increased risk of admission in the newborn intensive care unit, APGAR scores less than 7 at 5 min, large for gestational age, macrosomia, extreme pre-term birth in pregnant mothers compared with standard BMI mothers. However, the underweight mothers showed increased odds for small for gestational age infant and pre-term birth, whereas obese mothers were at higher risk for post-term birth and stillbirths. The subgroup and meta-regression analyses have shown the impact of BMI cut-offs, geographical region, source of BMI, and sample size on several maternal, fetal/neonatal adverse outcomes.
The meta-analysis confirmed the association of elevated pre-pregnancy maternal BMI with higher odds of adverse maternal and fetal/neonatal outcomes.
Maternal obesity in prolonged pregnancy: Labor, mode of delivery, maternal and fetal outcomes
2021, Journal of Gynecology Obstetrics and Human Reproduction
Obesity is currently not a medical indication for elective induction of labor although obese patients may not be eligible for expectant management after 41 W G. Few data on labor and complications in this population undergoing prolonged pregnancy are known. The objective of our study was to evaluate labor, mode of delivery, maternal and fetal outcomes in prolonged pregnancy in obese patients compared to normal body mass index (BMI).
It was a retrospective cohort study in patients who, after prolonged pregnancy gave birth to a single fetus, in cephalic presentation, between the first of January 2002 and December 31, 2018 in the Caen University Hospital Center. Patient’s characteristics were compared within each BMI class using uni- and multivariate analysis with regression logistics models.
Overall, 9159 patients were included. Term of birth and spontaneous labor calculated rates were significantly increased in case of obesity (p < 0.001). The adjusted Odds Ratio (ORa) for induced labor in class III obesity was 1.73 [1.13−2.66]. After induction of labor, 83.0 % patients with normal BMI delivered vaginally versus 61.8 % in case of class III obesity (p < 0.001). The ORa for an emergency cesarean was 3.39 [2.04–5.63] and 1.78 [1.06−2.99] for neonatal morbidity in class III obesity.
Morbid obese patients do not belong to a low risk patient’s group when pregnancy is prolonged. Elective induction in case of morbid obesity may entail less risk than allowing the pregnancy to progress after 41 W G or even 39 W G. Further randomized prospective studies are nevertheless required.
The Edmonton Obesity Staging System Predicts Mode of Delivery After Labour Induction
2020, Journal of Obstetrics and Gynaecology Canada
This study sought to evaluate the use of the Edmonton Obesity Staging System (EOSS) in predicting cesarean delivery among term, nulliparous, singleton pregnancies in women with overweight or obesity who are undergoing an induction of labour.
A prospective cohort study was performed in Edmonton, Alberta. Women undergoing an induction of labour at term were recruited to either a sample cohort, including women with a body mass index of ≥25 kg/m² at first antenatal visit, or a control cohort with a body mass index of 18.5 to 24.9 kg/m². Participating women provided a self-reported health history and consented to review of their medical records allowing allocation into EOSS categories. The primary outcome was the rate of cesarean delivery based on EOSS category. Secondary outcomes consisted of a summary score of adverse maternal, delivery, and neonatal events (Canadian Task Force Classification II-2).
Overall, 345 women were recruited, with a participation rate of 93.7%. The sample cohort consisted of 276 women with overweight or obesity, whereas the control cohort included 69 normal-weight women. The overall rate of cesarean delivery was 30.4% for the control cohort and 35.8%, 29.9%, 43.2%, and 90.5% for women assigned an EOSS category 0, 1, 2, and 3, respectively (P < 0.001). A summary score was not indicative of overall rate of adverse maternal, delivery, and neonatal events (P = 0.22).
The EOSS may help predict the chance of cesarean delivery in a high-risk group of nulliparous women with overweight or obesity who are undergoing an induction of labour at term.
Cette étude visait à évaluer l'utilisation du système de classification de l'obésité EOSS (Edmonton Obesity Staging System) pour prédire la probabilité d'un accouchement par césarienne en cas de déclenchement artificiel du travail d'une grossesse monofœtale à terme chez une femme nullipare en surpoids ou atteinte d'obésité.
Une étude de cohorte prospective a été réalisée à Edmonton en Alberta. Les chercheurs ont recruté des femmes devant subir un déclenchement artificiel du travail d'une grossesse à terme et les ont réparties en deux groupes : soit dans un groupe-échantillon de femmes ayant un indice de masse corporelle de 25 kg/m² ou plus lors de la première consultation de suivi prénatal, soit dans un groupe témoin de femmes ayant un indice de masse corporelle de 18,5 à 24,9 kg/m². Les participantes ont autodéclaré leurs antécédents médicaux et consenti à l'examen de leur dossier médical aux fins de classification en fonction des catégories de l'EOSS. Le taux de césariennes fondé sur la classification de l'EOSS constituait le critère de jugement principal. Les critères de jugement secondaires consistaient en un indice global des événements défavorables maternels, obstétricaux et néonataux (classification II-2 du Groupe d'étude canadien sur les soins de santé préventifs).
Un total de 345 femmes ont été recrutées pour cette étude, laquelle présente un taux de participation de 93,7 %. Le groupe-échantillon se compose de 276 femmes en surpoids ou atteintes d'obésité, tandis que le groupe témoin comprend 69 femmes de poids normal. Le taux de césariennes global est de 30,4 % pour les femmes du groupe témoin et de 35,8 %, 29,9 %, 43,2 % et 90,5 % respectivement pour les femmes classées dans les catégories 0, 1, 2 et 3 selon l'EOSS (P < 0,001). Un indice global ne s'est pas avéré révélateur du taux global d'événements défavorables maternels, obstétricaux et néonataux (P = 0,22).
L'EOSS pourrait aider à prédire la probabilité d'accouchement par césarienne dans un groupe à risque élevé de femmes nullipares en surpoids ou atteintes d'obésité en cas de déclenchement artificiel du travail d'une grossesse à terme.
Intrapartum care for obese and morbidly obese women
2020, Obesity and Obstetrics
There is good evidence that maternal obesity contributes to poorer outcomes for both the woman and her baby during delivery. Known complications include increased risks for induction of labour, caesarean section, postpartum hemorrhage, infection, longer duration of hospital stay, macrosomia, and higher perinatal morbidity and mortality. Obese women are more likely to be admitted earlier in labour, require higher doses of oxytocin, and have longer labours. The risk of caesarean section, which is more difficult and associated with increased morbidity in obese women, is two to three times that of the general obstetric population. Due to the increased risks associated with obesity, and the intrapartum challenges that may arise, specific planning of delivery and optimal fetal monitoring are required for the obese parturient, as while a number of these woman may have uncomplicated deliveries, many will not. The need for supervision and attendance by senior obstetric staff is increased.

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: Supported by grant HD01262 from the National Institute of Child Health and Human Development.

: Cite this article as: Stotland NE, Washington AE, Caughey AB. Prepregnancy body mass index and the length of gestation at term. Am J Obstet Gynecol 2007;197:378.e1-378.e5.

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SMFM meeting paperPrepregnancy body mass index and the length of gestation at term

Objective

Study Design

Results

Conclusion

Section snippets

Materials and Methods

Results

Comment

Am J Obstet Gynecol

Am J Obstet Gynecol

Am J Obstet Gynecol

Am J Obstet Gynecol

Obstet Gynecol

Am J Obstet Gynecol

Am J Obstet Gynecol

Obstet Gynecol

Obstet Gynecol

Obstet Gynecol

Stillbirths and rate of neonatal deaths in 76,761 postterm pregnancies in Sweden, 1982-1991: a register study

Acta Obstet Gynecol Scand

Complications of term pregnancies beyond 37 weeks of gestation

Obstet Gynecol

SMFM meeting paper
Prepregnancy body mass index and the length of gestation at term