Population-based trends of pregnancy outcome in obese mothers: what has changed over 15 years

The association between body mass index and live birth and maternal and perinatal outcomes after in-vitro fertilization: a national cohort study

Objective

To investigate the association between female body mass index (BMI) and live birth rates and maternal and perinatal outcomes after in-vitro fertilization (IVF).

Methods

We performed a national, population-based cohort study including women undergoing IVF between 2002 and 2020. The cohort included 126,620 fresh cycles and subsequent frozen embryo transfers between 2007 and 2019 (subpopulation 1) and 58,187 singleton deliveries between 2002 and 2020 (subpopulation 2). Exposure was female BMI (kg/m2) categorized according to the World Health Organization as underweight (<18.5), normal weight (18.5-24.9, reference), overweight (25.0-29.9), class I obesity (30.0-34.9), class II obesity (35.0-39.9), and class III obesity (≥40.0). The primary outcome in subpopulation 1 was cumulative live birth per started fresh IVF cycle, including fresh and subsequent frozen embryo transfers. Primary outcomes in subpopulation 2 were hypertensive disorders of pregnancy and preterm birth at less than 37 weeks. Risk ratios (RRs) with 95% confidence intervals (CIs) for the association between BMI class and outcomes were calculated using generalized linear models after adjustment for relevant confounders.

Results

The cumulative live birth rate decreased significantly with increasing BMI from 32.6% in normal-weight women to 29.4% in overweight women, 27.0% in women in obesity class I, 21.8% in women in obesity class II, and 7.6% in women in obesity class III. The risk of hypertensive disorders of pregnancy increased significantly and progressively with increasing BMI, from 4.6% in normal-weight women to 7.8% in overweight women and 12.5%, 17.9%, and 20.3% in women in obesity classes I, II, and III. The risk of preterm birth followed a similar pattern, from 6.3% in normal-weight women to 7.5% in overweight women and 8.9%, 9.9%, and 15.3% in women in obesity classes I, II, and III. The risks of other perinatal complications, such as perinatal death, showed an even more pronounced increase.

Conclusion

Using a large and complete national cohort of women undergoing IVF, we demonstrate a dose-dependent decrease in live birth rate and a substantial increase in maternal and perinatal complications with increasing BMI. Strategies to improve this situation are warranted.

Incidence of obese parturients and the outcomes of their pregnancies: A nationwide register study in Finland

OBJECTIVES

We analyzed the incidence of obese and severely obese parturients and the impact of maternal obesity on mode of delivery, perinatal and neonatal mortality, and neonatal health.

STUDY DESIGN

We included all singleton births from the medical birth register of Finland from 2004 to 2018 (n = 792 437). Maternal body mass index (BMI) was categorized into three classes: non-obese (BMI < 30 kg/m²), obese (BMI 30 - 39.9 kg/m²), and morbidly obese (BMI 40 kg/m² or more). The yearly incidence of obese and severely obese parturients per 10000 births was calculated. Logistic regression was used to calculate adjusted odds ratios (aOR) with 95% confidence intervals (CI).

RESULTS

Between 2004 and 2018, the incidence of obese and morbidly obese parturients increased by 44% and 103%, respectively. Cesarean section rates were 23.6% and 30%, respectively (aOR 1.63 CI 1.61 - 1.66 and 2.33 CI: 2.23 - 2.44). Neonates born to morbidly obese parturients had an increased need for intensive care unit treatment (aOR 2.21 CI: 2.10 - 2.32), higher perinatal mortality (aOR 1.65 CI: 1.28 - 2.14), and higher neonatal mortality (aOR 1.68 CI: 1.04 - 2.72). The need for neonatal intensive care (aOR 1.50 CI: 1.47 - 1.53), perinatal mortality (aOR 1.25 CI: 1.13 - 1.39), and neonatal mortality (aOR 1.33 CI: 1.09 - 1.62) increased also among obese parturients.

CONCLUSIONS

We report a worrying increase in obese and morbidly obese parturients. Neonates born to these parturients were more likely delivered by cesarean sections and had higher rates of perinatal and neonatal mortality, and intensive care unit treatment. This highlights the importance of preventing obesity among fertile-aged females.

Birth risks according to maternal height and weight - an analysis of the German Perinatal Survey

Objective To investigate the variability in the prevalences of selected birth risks in women of different heights and weights. Methods Data from the German Perinatal Survey of 1998-2000 were analyzed: 503,468 cases contributed to our analysis of the prevalences of selected birth risks specified according to maternal weight groups, 502,562 cases contributed to our analysis according to maternal height groups and 43,928 cases contributed to our analysis of birth risks in women with a body mass index (BMI) of 21-23 kg/m2 but different heights and weights. Data analysis was performed using SPSS version 22. Results Some birth risks varied substantially by maternal height in women with a "normal" BMI of 21-23 kg/m2: the prevalence of post-term birth increased from 8.7% in women with a height of 150 cm to 13.5% in 185 cm tall women, the prevalence of preterm birth decreased from 5.9% (150 cm tall women) to 3.1% (185 cm tall women), a pathologic cardiotocography (CTG) or poor fetal heart sounds on auscultation occurred in 19.4% of the 150 cm tall women but only in 9.2% of 185 cm tall women and cephalopelvic disproportion decreased from 12.3% (150 cm tall women) to 1.2% (185 cm tall women). Analyses of women in different body height and weight groups (without restriction of BMI) likewise showed differences in the prevalences of some birth risks. Conclusion Birth risks may vary by height and weight in women with the same, "normal" BMI. BMI should not be the only way by which the impact of maternal height and weight is assessed with regard to perinatal outcomes such as birth risks.

The association between maternal nutrition and lifestyle during pregnancy and 2-year-old offspring adiposity: analysis from the ROLO study

Aim

To examine the association between maternal nutrition and lifestyle factors and offspring adiposity, using baseline and 2-year postpartum follow-up data from a randomised control trial of low glycaemic index diet.

Subject and methods

Food diaries and lifestyle questionnaires were completed during pregnancy and infant feeding and maternal lifestyle questionnaires 2 years postpartum for 281 mother and infant pairs from the ROLO study. Maternal anthropometry was measured throughout pregnancy and infant and maternal anthropometry was measured 2 years postpartum.

Results

Maternal 2 year postpartum body mass index (BMI) was positively associated with offspring BMI-for-age z-score (B = 0.105, p = 0.015). Trimester 2 saturated fat intake was positively associated with offspring subscapular:triceps skinfold ratio (B = 0.018, p = 0.001). Trimester 1 glycaemic index was also positively associated with offspring sum of subscapular and triceps skinfolds (B = 0.009, p = 0.029).

Conclusions

Maternal BMI 2 years postpartum was positively associated with offspring BMI. Pregnancy saturated fat intake was positively and polyunsaturated fat negatively associated with offspring adiposity. While further research is necessary, pregnancy and the postpartum period may be early opportunities to combat childhood obesity.

Electronic supplementary material

The online version of this article (doi:10.1007/s10389-016-0740-9) contains supplementary material, which is available to authorized users.

The association between body mass index and preeclampsia: a meta-analysis

BACKGROUND

Several observational studies have reported a positive association between elevated body mass index (BMI) and preeclampsia, but no meta-analysis has been conducted yet. This meta-analysis was conducted to estimate the overall association between overweight or obesity and preeclampsia.

METHODS

Major electronic databases, including PubMed, Web of Science, and Scopus were searched until August 2015. The reference lists of included studies were screened as well. Epidemiological studies addressing the association between BMI and preeclampsia were enrolled. The heterogeneity across studies was explored by Q-test and I(2) statistic. The possibility of publication bias was assessed using Begg's and Egger's tests. The results were reported using odds ratio (OR) estimate with its 95% confidence intervals (CI) using a random-effects model.

RESULTS

We identified a total of 1298 references and included 23 studies with 1 387 599 participants. Preeclampsia was associated with overweight (OR = 1.73; 95% CI: 1.59, 1.87; 21 studies; I(2 )=( )62.3%) and obesity (OR = 3.15; 95% CI: 2.96, 3.35; 22 studies; I(2 )=( )36.0%). There was no evidence of publication bias.

CONCLUSIONS

There is sufficient evidence that excess body mass index is significantly associated with an increased risk of preeclampsia. Therefore, overweight and obesity can be considered as a predictor of preeclampsia.

Trends in Indigenous and non-Indigenous caesarean section births in the Northern Territory of Australia, 1986-2012: a total population-based study

OBJECTIVE

To examine trends in caesarean section deliveries and factors associated with these trends for Indigenous and non-Indigenous mothers.

DESIGN

Total population-based study.

SETTING

Northern Territory of Australia, 1986-2012.

POPULATION

Pregnancies among Northern Territory residents, limited to singleton live births with cephalic presentations delivered at 37-42 weeks' gestation (n = 78 561).

METHODS

Descriptive analyses of demographic and obstetric risk factors. Poisson regression with robust variance to estimate the likelihood of caesarean delivery with and without labour compared with vaginal delivery, over time and between Indigenous and non-Indigenous mothers, adjusting for risk factors.

MAIN OUTCOME MEASURES

Trends in caesarean sections and risk of caesarean delivery compared with vaginal delivery.

RESULTS

The total rate of caesarean deliveries in the Northern Territory increased between 1986 and 2012. From the year 2000, the rise was driven by increases in caesareans with labour among nulliparous mothers and no labour caesareans among multiparous mothers. Increases in demographic and obstetric risk factors explained the rise in caesareans with labour among nulliparous Indigenous mothers, whereas other unmeasured variables contributed to the rise among non-Indigenous mothers. Increases in previous caesarean delivery contributed to the rise in all caesareans among multiparous mothers. Following adjustment, the risk of Indigenous nulliparous mothers having a caesarean with labour was 47% greater than for non-Indigenous nulliparous mothers [adjusted risk ratio 1.47 (95% CI 1.34-1.60)].

CONCLUSIONS

Increases in demographic and obstetric risk factors partially explained the increase in caesarean rates in the Northern Territory and the contribution of these factors differed between Indigenous and non-Indigenous mothers.

TWEETABLE ABSTRACT

Caesarean section rates increased between 1986 and 2012 in the Northern Territory of Australia.

Immune Mechanisms Linking Obesity and Preeclampsia

Preeclampsia (PE) is characterized by hypertension occurring after the twentieth week of pregnancy. It is a significant contributor to maternal and perinatal morbidity and mortality in developing countries and its pervasiveness is increasing within developed countries including the USA. However, the mechanisms mediating the pathogenesis of this maternal disorder and its rising prevalence are far from clear. A major theory with strong experimental evidence is that placental ischemia, resulting from inappropriate remodeling and widening of the maternal spiral arteries, stimulates the release of soluble factors from the ischemic placenta causing maternal endothelial dysfunction and hypertension. Aberrant maternal immune responses and inflammation have been implicated in each of these stages in the cascade leading to PE. Regarding the increased prevalence of this disease, it is becoming increasingly evident from epidemiological data that obesity, which is a state of chronic inflammation in itself, increases the risk for PE. Although the specific mechanisms whereby obesity increases the rate of PE are unclear, there are strong candidates including activated macrophages and natural killer cells within the uterus and placenta and activation in the periphery of T helper cells producing cytokines including TNF-α, IL-6 and IL-17 and the anti-angiogenic factor sFlt-1 and B cells producing the agonistic autoantibodies to the angiotensin type 1 receptor (AT1-aa). This review will focus on the immune mechanisms that have been implicated in the pathogenesis of hypertension in PE with an emphasis on the potential importance of inflammatory factors in the increased risk of developing PE in obese pregnancies.

Exploring the relationship between maternal body mass index and offspring birth weight: Analysis of routinely collected data from 1967 to 2010 in Aberdeen, Scotland

A retrospective cohort study was undertaken to assess the relationship between maternal body mass index (BMI) and neonatal birth weight. Data were extracted from Aberdeen Maternity and Neonatal Databank on all deliveries (n = 94049) occurring between 1967 and 2010. Compared with mothers whose weight was in the normal range, the adjusted odds of delivering a high-birth-weight infant were 0.63 (95% confidence interval: 0.59, 0.67), 1.44 (1.39, 1.50); 1.83 (1.72, 1.95); 2.22 (2.04, 2.43) in underweight, overweight, obese and morbidly obese mothers, respectively. Similarly, the adjusted odds of delivering a low-birth-weight baby decreased with increasing maternal BMI from 1.38 (1.23, 1.55) in underweight women to 0.80 (0.72, 0.89) in overweight women; 0.78 (0.67, 0.93) in obese and 0.56 (0.44, 0.71) in morbidly obese mothers. These relationships were only evident after adjustment for gestational age, presumably because higher maternal BMI is also, in some cases, associated with pre-term deliveries.

Prepregnancy obesity trends among low-income women, United States, 1999-2008

There is limited data on prepregnancy obesity trends specifically among low-income women, a population at high risk for obstetric complications. Using the Pregnancy Nutrition Surveillance System, we assessed prepregnancy obesity [body mass index (BMI) ≥ 30 kg/m(2)] trends among women who participated in the Supplemental Nutrition Program for Women, Infants, and Children in 1999, 2004, and 2008. Prepregnancy BMI was calculated using measured height and self-reported prepregnancy weight. We report unadjusted contributor (state, territory or Indian tribal organization) specific trends, and both unadjusted and adjusted overall trends, to account for changes in maternal age and race-ethnic distributions, using 1999 as the referent. Of the 27 contributors in 1999, 2 had a prepregnancy obesity prevalence <20%, and 1 had a prevalence ≥ 30%. Of the 35 contributors in 2008, none had a prepregnancy obesity prevalence <20%, and 14 had a prevalence ≥ 30%. From 1999 to 2008, the overall prevalence of prepregnancy obesity increased among all racial-ethnic groups, except among American Indian/Alaskan Natives, where it remained high, but stable. Overall prepregnancy obesity increased most rapidly among Hispanics, and remained stable from 2004 to 2008 among non-Hispanic blacks. In 2008, prevalence was highest among American Indian/Alaskan Natives (36.1%) and lowest among Asians/Pacific Islanders (10.8%). The adjusted prepregnancy obesity prevalence increased from 24.8% in 1999 to 28.3% in 2008, a relative increase of 14.1%. Prepregnancy obesity among low-income women increased from 1999 to 2008 and varied by race-ethnicity. These data can be used by obesity prevention programs to better target high-risk women.