Is birth weight modified during pregnancy? Using sibling differences to understand the impact of blood glucose, obesity, and maternal weight gain in gestational diabetes

Does anti-HPA-1a affect birthweight in fetal and neonatal alloimmune thrombocytopenia?

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) ensues from parental incompatibility for platelet alloantigens with maternal sensitization. HPA-1a/1b incompatibility is the most common cause of FNAIT in Caucasians. Placental villitis and lower birthweight in FNAIT suggest anti-HPA-1a may have effects beyond inducing thrombocytopenia.

OBJECTIVES

Does FNAIT secondary to anti-HPA-1a result in smaller newborns and, the corollary, does antenatal management of FNAIT increase birthweight?

STUDY DESIGN

Birthweights of 270 FNAIT-affected newborns from a randomized clinical trial and a NAITbabies.org survey (135 paired siblings) were compared with those of published controls and treated to untreated FNAIT-affected siblings. Birthweights were converted to percentiles to account for gestational age, sex, and role of birth order in birth weight. Body weights of FNAIT-affected and -unaffected pups in a mouse FNAIT model were analyzed.

RESULTS

Untreated siblings in both the clinical trial and NAITbabies.org cohorts were not small, compared with normal controls. However, treated siblings in both cohorts had significantly higher birthweight percentiles compared with their previous untreated affected sibling. After accounting for gestational age, sex, and birth order, increased birthweight percentile in treated compared with the untreated siblings remained significant in both cohorts. FNAIT-affected neonatal mice had lower bodyweights than FNAIT-unaffected pups.

CONCLUSIONS

Untreated FNAIT-affected newborns were not small; however, treatment of FNAIT-affected pregnancies increased newborn birthweights despite corrections to account for other factors that might have influenced the results. High dose IVIG is believed to "block" FcRn and lower maternal anti-HPA-1a levels, and thus increase birthweights by reducing levels of maternal anti-HPA-1a and reducing placental villitis.

Maternal prepregnancy BMI and size at birth: race/ethnicity-stratified, within-family associations in over 500,000 siblings

PURPOSE

To estimate racial/ethnic-stratified effects of maternal prepregnancy BMI on size for gestational age at birth, by comparing siblings within families.

METHODS

This study examined linked vital statistics and patient discharge data from 580,960 infants born to 278,770 women in the State of California (2007-2012). To control for family-level confounding, we used fixed effects multinomial regression, modeling size for gestational age (small [SGA], appropriate, large [LGA]) as a function of maternal BMI (underweight, normal weight, overweight, obesity class I, II, III) and time-varying covariates. We conducted overall and race/ethnicity-stratified (non-Hispanic white, black, Asian; Hispanic) analyses. For comparison, we fit analogous random effects models, which do not control for family-level confounding.

RESULTS

In fixed effects models, maternal BMI was most strongly associated with LGA in non-Hispanic white women, reaching 6.7 times greater for class III obesity (OR [95% CI]: 6.7 [5.1, 8.7]); and weakest in black women (OR [95% CI]: 3.0 [1.5, 5.7]). Associations with SGA were similar across race/ethnicity. Compared with random effects estimates, fixed effects were most attenuated for LGA associations among racial/ethnic minority women.

CONCLUSIONS

Maternal prepregnancy BMI was differentially associated with size for gestational age across racial/ethnic groups, with the strongest family-level confounding in racial/ethnic minority women.

Is the Association Between Pregnancy Weight Gain and Fetal Size Causal?: A Re-examination Using a Sibling Comparison Design

BACKGROUND

Observational cohort studies have consistently shown that maternal weight gain in pregnancy is positively associated with fetal size, but it is unknown whether the association is causal. This study investigated the effect of pregnancy weight gain on fetal growth using a sibling comparison design to control for unmeasured confounding by genetic and shared environmental factors.

METHODS

Our study population included 44,457 infants (21,680 women) with electronic medical records in the Stockholm-Gotland Obstetrical Database, 2008-2014. We standardized pregnancy weight gain into gestational age-specific z-scores. Fetal size was classified as birthweight (gram), and as small- and large-for-gestational-age birth (birthweight <10th or >90th percentiles, respectively). Our sibling comparison analyses used multivariable linear fixed effects models for birthweight and hybrid logistic fixed effects models for small- and large-for-gestational-age birth (SGA and LGA). We repeated analyses using conventional (unmatched) regression models.

RESULTS

Sibling comparison analyses showed a clinically meaningful association between weight gain and fetal size (e.g., adjusted difference of +89 g birthweight [95% CI = 82, 95 g]; adjusted risk ratios [aRR] for SGA of 0.80 [95% CI = 0.75, 0.86] per 1 z-score increase in weight gain for a woman of body mass index [BMI] = 25). These findings were consistent across the range of BMI. Estimates were only modestly attenuated compared with conventional approach (+97 g [95% CI = 92, 102 g], aRR for SGA of 0.70 [95% CI = 0.67, 0.73] per 1 z-score increase in weight gain).

CONCLUSION

The positive association between pregnancy weight gain and fetal size we found using a sibling comparison design suggests that this relation has minimal confounding by familial factors that remain constant between pregnancies.

Maternal and Early Childhood Determinants of Women's Body Size in Midlife: Overall Cohort and Sibling Analyses

Observational evidence suggests that adult body size has its roots earlier in life, yet few life-course studies have data on siblings with which to control for family-level confounding. Using prospective data from the Early Determinants of Mammographic Density Study (n = 1,108; 1959-2008), we examined the association of maternal prepregnancy body mass index (BMI; weight (kg)/height (m)2), gestational weight gain (GWG), birth size, and childhood growth factors with adult BMI in daughters at midlife using quantile, linear, and logistic regression models. We compared overall cohort findings (n = 1,108) with sibling differences (n = 246 sibling sets). Results derived by all 3 regression methods supported positive and independent associations of prepregnancy BMI, GWG, and percentile change in early childhood growth with BMI in daughters at midlife. Sibling analyses demonstrated that higher GWG was independently related to a higher adult BMI in daughters, particularly for the highest 90th quantile of adult BMI (β = 0.64 (standard error, 0.26) BMI units). Greater increases in weight percentiles between 1 and 4 years of age within siblings were also associated with higher adult BMI in the 75th quantile (β = 0.06 (standard error, 0.03) kg). Thus, even after consideration of the role of family-level fixed effects, maternal GWG and childhood weight gain are associated with adult body size in midlife.

Associations of neonatal high birth weight with maternal pre-pregnancy body mass index and gestational weight gain: a case-control study in women from Chongqing, China

OBJECTIVES

To examine the associations of maternal pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) with neonatal high birth weight (HBW) in a sample of Chinese women living in southwest China.

METHODS

A hospital-based case-control study was conducted in Chongqing, China. A total of 221 mothers who delivered HBW babies (>4.0 kg) were recruited as cases and 221 age-matched (2-year interval) mothers with normal birth weight babies (2.5-4.0 kg) were identified as controls. ORs were estimated using conditional logistic regression analysis. For the analysis, pre-pregnancy BMI was categorised as underweight/normal weight/overweight and obesity and GWG was categorised as inadequate/appropriate/excessive.

RESULTS

Among the cases, mean pre-pregnancy BMI was 21.8±2.8 kg/m(2), mean GWG was 19.7±5.1 kg and mean neonatal birth weight was 4.2±0.2 kg. In the controls, the corresponding values were 21.1±3.1 kg/m(2), 16.4±5.0 kg and 3.3±0.4 kg, respectively. More cases than controls gained excessive weight during pregnancy (80.1% vs 48.4%, p<0.001). No significant association was found between pre-pregnancy BMI and HBW babies (OR=1.04, 95% CI 0.97 to 1.11; p>0.05). GWG was positively related to HBW after adjustment for gravidity, gestational age, newborns' gender and family income (OR=1.18, 95% CI 1.12 to 1.25; p<0.001). The adjusted OR of delivering HBW babies was 5.39 (95% CI 2.94 to 9.89; p<0.001) for excessive GWG versus appropriate GWG. This OR was strengthened among pre-pregnancy normal weight women (OR=10.27, 95% CI 3.20 to 32.95; p<0.001).

CONCLUSIONS

Overall, the findings suggest a significantly positive association between GWG and HBW. However, pre-pregnancy BMI shows no independent relationship with HBW.

Maternal weight gain in excess of pregnancy guidelines is related to daughters being overweight 40 years later

BACKGROUND

Exceeding the Institute of Medicine guidelines for pregnancy weight gain increases childhood and adolescent obesity. However, it is unknown if these effects extend to midlife.

OBJECTIVE

We sought to determine if exceeding the Institute of Medicine guidelines for pregnancy weight gain increases risk of overweight/obesity in daughters 40 years later.

STUDY DESIGN

This cohort study is based on adult offspring in the Child Health and Development Studies and the Collaborative Perinatal Project pregnancy cohorts originally enrolled in the 1960s. In 2005 through 2008, 1035 daughters in their 40s were recruited to the Early Determinants of Mammographic Density study. We classified maternal pregnancy weight gain as greater than vs less than or equal to the 2009 clinical guidelines. We used logistic regression to compare the odds ratios of daughters being overweight/obese (body mass index [BMI] ≥25) at a mean age of 44 years between mothers who did not gain or gained more than pregnancy weight gain guidelines, accounting for maternal prepregnant BMI, and daughter body size at birth and childhood. We also examined potential family related confounding through a comparison of sisters using generalized estimating equations, clustered on sibling units and adjusted for maternal age and race.

RESULTS

Mothers who exceeded guidelines for weight gain in pregnancy were more likely to have daughters who were overweight/obese in their 40s (odds ratio [OR], 3.4; 95% confidence interval {CI}, 2.0-5.7). This magnitude of association translates to a relative risk (RR) increase of 50% (RR = 1.5; 95% CI, 1.3-1.6). The association was of the same magnitude when examining only the siblings whose mother exceeded guidelines in 1 pregnancy and did not exceed the guidelines in the other pregnancy. The association was stronger with increasing maternal prepregnancy BMI (P trend < .001). Compared to mothers with BMI <25 who did not exceed guidelines, the relative risks (RR) for having an overweight/obese adult daughter were 1.3 (95% CI, 1.1-1.7), 1.7 (95% CI, 1.4-2.1) and 1.8 (95% CI, 1.5-2.1), respectively, if mothers exceeded guidelines and their prepregnancy BMI was <25, overweight (BMI 25-<30), or obese (BMI >30). This pattern held irrespective of daughters' weight status at birth, at age 4 years, or at age 20 years.

CONCLUSION

Our findings support that obesity prevention before pregnancy and strategies to maintain weight gain during pregnancy within the IOM guidelines might reduce the risk of being overweight in midlife for the offspring.

Maternal obesity and occurrence of fetal macrosomia: a systematic review and meta-analysis

OBJECTIVE

To determine a precise estimate for the contribution of maternal obesity to macrosomia.

DATA SOURCES

The search strategy included database searches in 2011 of PubMed, Medline (In-Process & Other Non-Indexed Citations and Ovid Medline, 1950-2011), and EMBASE Classic + EMBASE. Appropriate search terms were used for each database. Reference lists of retrieved articles and review articles were cross-referenced.

METHODS OF STUDY SELECTION

All studies that examined the relationship between maternal obesity (BMI ≥30 kg/m(2)) (pregravid or at 1st prenatal visit) and fetal macrosomia (birth weight ≥4000 g, ≥4500 g, or ≥90th percentile) were considered for inclusion.

TABULATION, INTEGRATION, AND RESULTS

Data regarding the outcomes of interest and study quality were independently extracted by two reviewers. Results from the meta-analysis showed that maternal obesity is associated with fetal overgrowth, defined as birth weight ≥ 4000 g (OR 2.17, 95% CI 1.92, 2.45), birth weight ≥4500 g (OR 2.77,95% CI 2.22, 3.45), and birth weight ≥90% ile for gestational age (OR 2.42, 95% CI 2.16, 2.72).

CONCLUSION

Maternal obesity appears to play a significant role in the development of fetal overgrowth. There is a critical need for effective personal and public health initiatives designed to decrease prepregnancy weight and optimize gestational weight gain.

Differences in gestational weight gain between pregnancies before and after maternal bariatric surgery correlate with differences in birth weight but not with scores on the body mass index in early childhood

BACKGROUND

Large maternal gestational weight gain (GWG) is associated with increased birth weight and increased risk of obesity in offspring, but these associations may be confounded by genetic and environmental factors. The aim was to investigate the effects of differences in GWG in all three trimesters on differences in birth weight and in body mass index (BMI) scores at 4 and 6 years of age, within siblings born before and after bariatric surgery.

METHOD

Women with at least one child born before and one after bariatric surgery were identified in national Swedish registers. Series of weight (and height) measurements were collected from antenatal medical records, with data on the nearest pregnancies before and after bariatric surgery.

RESULTS

The age-adjusted means of pre- and post-operative GWG of 124 women were 11.3 (standard deviation [SD] 7.2) and 8.3 (SD 6.4) kg, respectively (P = 0.01). Adjusted fixed effects regression models showed positive associations of differences in mean total GWG with differences in siblings' birth weight, 0.023 kg per 1-kg greater weight gain (95% confidence interval [CI]: 0.014-0.069) and for second trimester 0.53 kg for each 1-kg greater weight per week (95% CI: 0.32-1.61), whereas no associations were found with BMI in pre-school age.

CONCLUSION

This study showed positive associations between differences in total and second trimester maternal GWG and differences in children's birth weight, but no association with BMI scores in pre-school age. Maternal genetic, social and lifestyle factors fixed from one pregnancy to the next were taken into account in the analyses by the study design.

Increased risk for overweight among Swedish children born to mothers with gestational diabetes mellitus

OBJECTIVE

Investigate the effects of maternal gestational diabetes mellitus (GDM) on height, weight, and body mass index (BMI) in offspring compared both to their siblings and to age-specific BMI reference values in Sweden. Their parents present BMI was also investigated.

METHODS

The growth of 232 offspring to 110 women with at least one pregnancy with GDM, were studied up to 12 yr of age. Height and weight of children were collected from Health Care Centres and compared to age-specific reference values in Sweden. Self-reported height and weight of the parents were collected at follow-up.

RESULTS

For boys, weight was higher at birth and at 8-10 yr of age, giving a higher BMI at 7-10 yr of age. Girls had an accelerated height growth at all ages, combined with an increased weight of varying degree resulting in higher BMI at birth and at 4-12 yr of age. A similar pattern was observed in siblings born after a normal pregnancy. Median BMI of mothers at follow-up was 25.4 (18.3-59.5 n = 105) and 26.5 (18.6-38.1 n = 90) for fathers.

CONCLUSIONS

Children born to mothers with prior GDM have a higher risk of overweight and obesity later in life. This is most likely due to life style habits rather than intrauterine factors, as the same BMI pattern was found in siblings born after a normal pregnancy. However, the design of the study could not rule out the role of genetic factors. Priority should be given to early life style intervention in these families.

Gestational diabetes: maternal weight gain in relation to fetal growth, treatment modality, BMI and glycemic control

OBJECTIVES

We sought to determine the impact of maternal weight gain on fetal growth in gestational diabetes (GDM) in relation to treatment modality, body mass index (BMI) and glycemic control.

STUDY DESIGN

Two thousand four hundred fifty-four GDMs were evaluated. Obesity was defined as BMI >29; good glycemic control ≤ 100 mg/dl; maternal age < and >30 years; parity ± 1; large for gestational age (LGA) >90th percentile and small for gestational age (SGA) <10th percentile.

RESULTS

SGA rates were similar in all groups. Obese/overweight diet-treated women in glycemic control showed a four-fold higher rate of LGA compared to insulin-treated women. A 36-lb weight gain in insulin-treated patients had a six-fold higher risk. In poor glycemic control, LGA rates were higher in all BMI/weight gain categories. Logistic regressions for LGA/SGA revealed that level of glycemia, weight gain, parity, obesity and treatment (for LGA only) were significant.

CONCLUSION

Different thresholds used for different maternal BMI categories in addition to the achievement of glycemic control and pharmacological therapy will enhance pregnancy outcome.

Birth weight and subsequent risk of obesity: a systematic review and meta-analysis

This report describes the association between birth weight (BW) and obesity. Screening of 478 citations from five electronic databases resulted in the inclusion of 33 studies, most of medium quality. The meta-analysis included 20 of these published studies. The 13 remaining articles did not provide sufficient dichotomous data and were systematically reviewed, revealing results consistent with the meta-analysis. Our results revealed that high BW (>4000 g) was associated with increased risk of obesity (odds ratio [OR], 2.07; 95% confidence interval [CI], 1.91-2.24) compared with subjects with BW ≤ 4000 g. Low BW (<2500 g) was associated with decreased risk of obesity (OR, 0.61; 95% CI, 0.46-0.80) compared with subjects with BW ≥ 2500 g. However, when two studies exhibited selection bias were removed, the results indicated no significant association between low BW and obesity (OR, 0.77; 95% CI, 0.58-1.04). Sensitivity analyses showed that differences in the study design, sample size and quality grade of the study had an effect on the low BW/obesity association, which low BW was not associated with the risk of obesity in cohort studies, studies with large sample sizes and studies with high quality grades. Pooled results were similar when normal birth weight (2500-4000 g) was used as the reference category. Subgroup analyses based on different growth and developmental stages (pre-school children, school children and adolescents) also revealed that high BW was associated with increased risk of obesity from childhood to early adulthood. No significant evidence of publication bias was present. These results suggest that high BW is associated with increased risk of obesity and may serve as a mediator between prenatal influences and later disease risk.

Pregnancy and obesity

Obesity has become a worldwide epidemic: it is associated with increased rate of infertility and with many pregnancy complications. Moreover, it is associated with gestational diabetes mellitus, which increases the risk of these complications. As the prevalence of obesity is increasing, so is the number of women in the reproductive age who are overweight and obese. This article addresses issues concerning pregravid obesity and weight gain during pregnancy and their implication on gestational diabetes and pregnancy outcome.

Relationship between increased relative birthweight and infections during pregnancy in children with a high-risk diabetes HLA genotype

AIMS/HYPOTHESIS

Children with high-risk type 1 diabetes HLA genotype have increased risk of high relative birthweight (HrBW), while cord blood islet autoantibodies decrease the risk. As gestational infections may affect offspring type 1 diabetes risk, the aims were to test whether: (1) children of mothers reporting gestational infections have increased HrBW; (2) gestational infections explain islet autoantibody reduction of HrBW; and (3) gestational infections affect the association between HLA and HrBW.

SUBJECTS AND METHODS

HLA genotypes and autoantibodies to glutamic acid decarboxylase, insulinoma-associated protein 2 and insulin were determined in cord blood of children born to non-diabetic mothers in the Diabetes Prediction in Skåne (DiPiS) study. Mothers reported gestational infections when the child was 2 months old.

RESULTS

Fever or gastroenteritis during pregnancy was reported by 2,848/19,756 mothers (14%); 339 in more than one trimester. Children whose mothers reported infections had increased risk of HrBW (p = 0.0003), particularly in the absence of cord blood islet autoantibodies (interaction between HrBW, islet autoantibodies and infections, p = 0.0005). The effect on HrBW by high-risk HLA-DQ2/8 was aggravated by infections in more than one trimester (odds ratio [OR] = 5.24; p = 0.003) (interaction; p = 0.022). When infections were reported, cord blood islet autoantibodies decreased HrBW (OR = 0.34; p = 0.0002).

CONCLUSIONS/INTERPRETATION

This study revealed that: (1) gestational fever, gastroenteritis, or both, increased the risk of HrBW; (2) cord blood islet autoantibodies decreased the risk of HrBW only in combination with infections; and (3) infections aggravated the association between HLA-DQ2/8 and HrBW. These data suggest an interaction between HLA, gestational infections, islet autoantibodies and fetal growth.