Overweight and obesity in mothers and risk of preterm birth and low birth weight infants: systematic review and meta-analyses

Associations of maternal pre-pregnancy obesity and excess pregnancy weight gains with adverse pregnancy outcomes and length of hospital stay

BACKGROUND

It is relatively less known whether pre-pregnancy obesity and excess gestational weight gain (GWG) are associated with caesarean delivery, pregnancy complications, preterm birth, birth and placenta weights and increased length of postnatal hospital stay.

METHODS

We used a population-based cohort of 6632 women who gave birth in Brisbane, Australia, between 1981 and 1983. The independent associations of pre-pregnancy obesity, GWG and institute of medicine (IOM) categories of combined pre-pregnancy BMI and GWG with outcomes were examined using multivariable regression (for continuous outcomes) and multivariable multinomial regression (for categorical outcomes) models.

RESULTS

We found women who were obese prior to pregnancy and women who gained excess weight during pregnancy were at greater risk for a pregnancy complications (OR: 2.10; 1.74, 2.54; age adjusted model), caesarean section (OR 1.29; 1.09, 1.54), higher birth weight difference (206.45 gm; 178.82, 234.08) and greater placental weight difference (41.16 gm; 33.83, 48.49) and longer length of hospital stay. We also found that mothers who gained inadequate weight or were underweight before pregnancy were at greater risk of preterm birth (2.27; 1.71, 3.00), lower risk of pregnancy complications (0.58; 0.44, 0.77) and had lower birth (-190.63;-221.05,-160.20) and placental (-37.16; -45.23,-29.09) weights. Results indicate that all associations remain consistent after adjustment for a range of potential confounding factors with the exception of the association between pre-pregnancy obesity and hospital stay.

CONCLUSIONS

Pre-pregnancy obesity or excessive GWG are associated with greater risk of pregnancy complications, caesarean delivery and greater birth and placenta weight. Excess GWG is associated with a longer stay in hospital after delivery, independent of pre-pregnancy BMI, pregnancy complications and caesarean delivery. In addition to pre-pregnancy obesity, it is vital that clinical practice considers excess GWG as another indicator of adverse pregnancy outcomes.

Prenatal amphetamine exposure and birth outcomes: a systematic review and metaanalysis

OBJECTIVE

The aim of this study was to systematically review the relationship between amphetamine exposure in pregnancy and birth outcomes.

STUDY DESIGN

Electronic databases were searched to identify relevant studies. Data from included studies were extracted by 2 reviewers. Summary odds ratio (OR) and confidence intervals (CIs) were calculated using the random effects model.

RESULTS

Ten studies were included. Significant increases in unadjusted risks of preterm birth (OR, 4.11; 95% CI, 3.05-5.55), low birthweight (OR, 3.97; 95% CI, 2.45-6.43), and small for gestational age (OR, 5.79; 95% CI, 1.39-24.06) were identified among women exposed to amphetamines in pregnancy. The mean birthweight was significantly lower among amphetamine-exposed pregnancies (mean difference, -279 g; 95% CI, -485 to -74 g). Two studies provided adjusted estimates on different outcomes, and their results were consistent with the findings from the unadjusted data.

CONCLUSION

Amphetamine exposure in pregnancy is associated with adverse birth outcomes and should be identified by physicians providing antenatal care.

The consequences of obesity and excess weight gain in pregnancy

The prevalence of obesity in pregnancy is rising exponentially; about 15–20% of pregnant women now enter pregnancy with a BMI which would define them as obese. This paper provides a review of the strong links between obesity and adverse pregnancy outcome which operate across a range of pregnancy complications. For example, obesity is associated with an increased risk of maternal mortality, gestational diabetes mellitus, thromboembolism, pre-eclampsia and postpartum haemorrhage. Obesity also complicates operative delivery; it makes operative delivery more difficult, increases complications and paradoxically increases the need for operative delivery. The risk of the majority of these complications is amplified by excess weight gain in pregnancy and increases in proportion to the degree of obesity, for example, women with extreme obesity have OR of 7·89 for gestational diabetes and 3·84 for postpartum haemorrhage compared to their lean counterparts. The consequences of maternal obesity do not stop once the baby is born. Maternal obesity programmes a variety of long-term adverse outcomes, including obesity in the offspring at adulthood. Such an effect is mediated at least in part via high birthweight; a recent study has suggested that the odds of adult obesity are two-fold greater in babies weighing more than 4 kg at birth. The mechanism by which obesity causes adverse pregnancy outcome is uncertain. This paper reviews the emerging evidence that hyperglycaemia and insulin resistance may both play a role: the links between hyperglycaemia in pregnancy and both increased birthweight and insulin resistance have been demonstrated in two large studies. Lastly, we discuss the nature and rationale for possible intervention strategies in obese pregnant women.

Altered contribution of RhoA/Rho kinase signaling in contractile activity of myometrium in leptin receptor-deficient mice

In late gestation, enhanced myometrial contractility is mediated in part through increased Rho/Rho kinase. Since leptin, which is elevated in pregnancy and obesity, can directly depress myometrial function, we hypothesized that in leptin receptor-deficient mice, myometrial contractility would be greater in late pregnancy due to increased Rho/Rho kinase activity. To test this, we correlated RhoA and Rho kinase expression to contractility in myometrium from nonpregnant (NP) and late-pregnant (P18) heterozygous leptin receptor-deficient mice (db/+) vs. wild-type (WT) mice. In NP mice, KCl-induced contractions were similar between WT and db/+ myometrium. However, the Rho kinase-dependent component of the contractions was greater in db/+ mice, along with an increased expression of Rho kinase. KCl-induced contractions increased in strength in myometrium from P18 WT and db/+ compared with NP. Although the contribution of Rho kinase to contractions was unchanged in P18 WT mice, it was decreased in P18 db/+ mice. The decrease in Rho kinase-dependent contractions in P18 db/+ mice coincided with reduced RhoA and Rho kinase expression relative to NP db/+. Addition of high-fat-induced abnormal glucose utilization prevented changes in Rho kinase function. We conclude that abnormal leptin signaling increases expression and function of Rho kinase to maintain contractile function in NP myometrium and that during pregnancy the contribution of RhoA and Rho kinase expression to myometrial function is reduced despite an increase in myometrial contractility. Thus, other signaling mechanisms appear to compensate when leptin signaling is reduced to maintain contractile function during pregnancy.

Low gestational weight gain and the risk of preterm birth and low birthweight: a systematic review and meta-analyses

BACKGROUND

Low gestational weight gain is common, with potential adverse perinatal outcomes.

OBJECTIVE

To determine the relation between low gestational weight gain and preterm birth and low birthweight in singletons in developing and developed countries.

DATA SOURCES

Medline, EMBASE and reference lists were searched, identifying 6,283 titles and abstracts.

METHODS OF STUDY SELECTION

Following the MOOSE consensus statement, two assessors independently reviewed titles, abstracts, full articles, extracted data and assessed quality.

RESULTS

Fifty-five studies, 37 cohort and 18 case-control, were included, involving 3,467,638 women. In the cohort studies (crude data, generally supported where available by adjusted data and case-control studies), women with low total gestational weight gain had increases in preterm birth <37 weeks [RR 1.64 (95%CI 1.62-1.65)], 32-36 weeks [RR 1.39 (95%CI 1.38-1.40)] and ≤ 32 weeks [RR 3.80 (95%CI 3.72-3.88)]. Low total gestational weight gain was associated with increased risks of low birthweight <2,500 g [RR 1.85 (95%CI 1.72-2.00)], in developing and developed countries [RR 1.84 (95%CI 1.71-1.99) and RR 3.02 (95%CI 1.37-6.63), respectively], 1,500-2,500 g [RR 2.02 (95%CI 1.88-2.17)] and <1,500 g (RR 2.00 (95%CI 1.67-2.40)]. Women with low weekly gestational weight gain were at increased risk of preterm birth [RR 1.56 (95%CI 1.26-1.94)], 32-36 weeks [RR 2.43 (95%CI 2.37-2.50)] and ≤ 32 weeks [RR 2.31 (95%CI 2.20-2.42)] but not low birthweight [RR 1.64 (95%CI 0.89-3.02)].

CONCLUSIONS

In this systematic review, we determined that singletons born to women with low total gestational weight gain have higher risks of preterm birth and low birthweight, with the lower the gain, the higher the risks.

Prepregnancy body mass index, smoking during pregnancy, and infant birth weight

PURPOSE

Smoking during pregnancy is strongly associated with increased risk of small for gestational age (SGA) and low birth weight, whereas elevated prepregnancy body mass index (BMI) is associated with a decreased risk of SGA and greater birth weight. We investigated the combined effect of prenatal smoking and prepregnancy BMI on risk of SGA and on birth weight.

METHODS

A total of 34,928 singleton, term pregnancies in residents of New York City between 1995 and 2003 were evaluated in multivariable regression models of birth weight and risk of SGA.

RESULTS

Increasing prepregnancy BMI reduced the risk of SGA and increased birth weight. The effect of prenatal smoking on birth weight and SGA diminished in women as their prepregnancy BMI increased, such that prenatal smoking did not significantly impact the risk of SGA among women who were overweight or obese before pregnancy. Prenatal smoking decreased mean birth weight by 187 g (95% confidence interval [CI] -337, -37) among underweight women, by 129 g(95% CI -170, -87) among normal weight women, by 46 g (95% CI -113, +20) among overweight women, and by 75 g (95% CI -162, +11) among obese women.

CONCLUSIONS

This study suggests that the effect of smoking during pregnancy on SGA and birth weight is present in underweight and normal weight women but markedly reduced among obese and overweight women.

[Nutritional characteristics of newborns of overweight and obese mothers]

INTRODUCTION

Maternal nutritional status is an important factor of adequate intrauterine growth and neonatal weight. The aim of this study is to evaluate the relationship between pre-gestational BMI (Body Mass Index) and breastfeeding duration, as well as infant anthropometric measurements during their first six months of life.

MATERIALS AND METHODS

Anthropometric measurements and the type of feeding were evaluated in a representative sample of 1,547 newborns from our population during 2009, according to their maternal BMI, and also in a sub-cohort of 759 infants followed up to 6 months of life.

RESULTS

A total of 72.9% of women had a normal weight, 18.7% were overweight and 8.4% obese. Women with a BMI ≥ 25 kg/m(2) had lower weight gain during pregnancy (P < .001), lower socioeconomic and cultural level (P < .001), and their infants had higher weight at delivery (P=.003) and at 6 months of life, with no differences in body length. Newborn weight increased in relation to maternal BMI, but over 35 kg/m(2) it decreased progressively (P < .001). Breastfeeding prevalence in obese women was 58.5% at hospital postpartum discharge, and 8.6% at six months of life; as opposed to 70.8% and 13.9%, respectively in women with normal BMI.

CONCLUSIONS

In our sample, maternal obesity is associated with a low socioeconomic and cultural level, higher infant weight at delivery and at 6 months of life, and less prevalence of exclusive breastfeeding; all of them nutritional risk factors in the short and long term.

[Probiotics and pregnancy]

Prenatal care is one of the great challenges in medicine. Aims of therapies and protocols may influence the life of mothers and babies. Diseases occurring during pregnancy are even more dangerous, because of the difficulties in their treatment strategy. Prevention must be emphasized using safe and natural drugs. Pre- and probiotics are in focus of the medical sciences. Various publications and studies emphasize the importance of these drugs in evidence-based medicine. Safe methods are essential in prenatal care. Authors review published data on the effect and potential use of pre- and probiotics during pregnancy.

Killing Me Softly: The Fetal Origins Hypothesis

In the epidemiological literature, the fetal origins hypothesis associated with David J. Barker posits that chronic, degenerative conditions of adult health, including heart disease and type 2 diabetes, may be triggered by circumstance decades earlier, in utero nutrition in particular. Economists have expanded on this hypothesis, investigating a broader range of fetal shocks and circumstances and have found a wealth of later-life impacts on outcomes including test scores, educational attainment, and income, along with health. In the process, they have provided some of the most credible observational evidence in support of the hypothesis. The magnitude of the impacts is generally large. Thus, the fetal origins hypothesis has not only survived contact with economics, but has flourished.

Pregnancy after bariatric surgery: a review

Maternal obesity is a major cause of obstetric morbidity and mortality. With surgical procedures to facilitate weight loss becoming more widely available and demanded and increasing number of women becoming pregnant after undergoing bariatric surgery, it is important and timely to consider the outcome of pregnancy following bariatric surgery. This paper aims to synthesize the current evidence regarding pregnancy outcomes after bariatric surgery. It concludes that bariatric surgery appears to have positive effects on fertility and reduces the risk of gestational diabetes and preeclampsia. Moreover, there appears to be a reduced incidence of fetal macrosomia post-bariatric procedure, although there remains uncertainty about the increased rates of small-for-gestational age and intrauterine growth restricted infants, as well as premature rupture of membranes in this group. A number of case reports highlight that pregnancy following bariatric surgery is not without complications and it must be managed as high risk by the multidisciplinary team.

Maternal underweight and the risk of preterm birth and low birth weight: a systematic review and meta-analyses

BACKGROUND

Despite the current obesity epidemic, maternal underweight remains a common occurrence with potential adverse perinatal outcomes. Our objective was to determine the relationship between maternal underweight and preterm birth (PTB) and low birth weight (LBW) in singleton pregnancies in developing and developed countries.

METHODS

We followed the MOOSE consensus statement. We searched MEDLINE and EMBASE from their inceptions. We included studies that assessed the effect of maternal underweight compared with normal weight according to body mass index in singleton gestations on our two primary outcomes: PTB (<37 weeks) and LBW (<2500 g). Two assessors independently reviewed citations, extracted data and assessed quality.

RESULTS

A total of 78 studies were included involving 1 025 794 women. The overall risk of PTB was increased in the cohort studies of underweight women [adjusted relative risk (RR) 1.29, 95% confidence interval (CI) 1.15-1.46], as were the risks of spontaneous PTB (adjusted RR 1.32, 95% CI 1.10-1.57) and induced PTB (adjusted RR 1.21, 95% CI 1.07-1.36). Underweight women had an increased risk of an LBW infant (adjusted RR 1.64, 95% CI 1.38-1.94). In developed countries, underweight women had an increased risk of PTB (RR 1.22, 95% CI 1.15-1.30) but not in developing countries (RR 0.99, 95% CI 0.67-1.45). In both developed and developing countries, underweight women were at increased risk of having an LBW infant (RR 1.48, 95% CI 1.29-1.68, and RR 1.52, 95% CI 1.25-1.85, respectively).

CONCLUSIONS

In this systematic review and meta-analyses, we determined that singletons born to underweight women have higher risks of PTB (overall, spontaneous and induced) and LBW than those born to women with normal weight.

Obesity and the placenta: A consideration of nutrient exchange mechanisms in relation to aberrant fetal growth

The obesity epidemic, including childhood obesity, is rapidly gaining strength as one of the most significant challenges to the health of the global community in the 21st Century. The proportion of women who are obese at the beginning of pregnancy is also increasing. These women and their babies are at high risk of pregnancy complications, and of programming for metabolic disease in adult life. In particular, maternal obesity is associated with aberrant fetal growth, encompassing both growth restricted and large for gestational age, or macrosomic fetuses. This article considers the potential effect of obesity and adipose tissue on placental nutrient exchange mechanisms in relation to aberrant fetal growth. The review emphasizes the dearth of work on this topic to date despite its importance to current and future healthcare of the population.

Maternal Pre-Pregnancy Obesity and Recurrent Wheezing in Early Childhood

A number of studies have linked obesity with asthma in adults and children. Few longitudinal studies have evaluated the effect of maternal pre-pregnancy obesity on either asthma or early childhood respiratory morbidity, and these have not been in urban, nonwhite populations. We sought to determine whether pre-pregnancy obesity was associated with recurrent wheezing in an urban, nonwhite population. This study includes 1,191 children from the Boston Birth Cohort (1998-present) followed prospectively to a mean age of 3.0 ± 2.4 years with study visits aligned with the pediatric primary care schedule. Multivariate logistic regression was used to evaluate the associations of maternal pre-pregnancy obesity (body mass index ≥30) with recurrent wheezing (≥4 lifetime episodes). Secondary outcomes included log-transformed cord-blood immunoglobulin E (Phadia), and physician diagnoses of eczema and food allergy. Pre-pregnancy obesity was present in 20.7% of mothers. Of the 1,191 children, 60 (5%) developed recurrent wheezing. Children of obese mothers had an increased risk of recurrent wheezing (adjusted odds ratio, 95% confidence interval: 3.51, 1.68-7.32). These associations persisted even after adjustment for fetal growth status. In contrast, maternal obesity was not associated with eczema or food allergy, and was inversely associated with log cord-blood immunoglobulin E (β, 95% confidence interval: -0.34, -0.66 to -0.02). In this predominantly urban, multiracial/ethnic birth cohort, maternal pre-pregnancy obesity was associated with an increased risk of recurrent wheezing. This association was not explained by fetal growth or increased atopy. Maternal pre-pregnancy obesity is a prevalent risk factor for respiratory morbidity in this urban, nonwhite population.