The Combined Effect of Maternal Body Mass Index and Smoking Status on Perinatal Outcomes - An Analysis of the German Perinatal Survey

Twenty-four-hour urinary protein excretion in uncomplicated singleton pregnancy

BACKGROUND

Twenty-four-hour urinary total protein excretion is an essential parameter used for evaluation of renal function and early detection of gestational complications. However, data on reference ranges of 24-hour urinary total protein excretion in normal pregnancy are scarce.

OBJECTIVE

This study aimed to determine reference ranges for 24-hour urinary total protein excretion in a population with uncomplicated singleton pregnancies using a standard method for urinary total protein. In addition, the values of 24-hour urinary total protein were stratified by maternal age and prepregnancy body mass index.

STUDY DESIGN

This study was based on a prospective cohort study in Shenzhen, China. The pregnant women were enrolled at their first prenatal clinical visit. All the participants were instructed to collect 24-hour urine samples during the following successive gestational periods: 6+0 to 13+6, 14+0 to 27+6, and 28+0 to 41+6 weeks. Total urinary protein excretion was analyzed by a colorimetric method. Ultimately, the study encompassed a total of 4844 pregnant women with uncomplicated pregnancies. The nonparametric percentile method was used to determine reference ranges for 24-hour urinary total protein excretion during different trimesters in women with uncomplicated pregnancies (excluding those with previous kidney disorders, gestational or chronic hypertension, preeclampsia, and pregestational diabetes mellitus, among others).

RESULTS

The 24-hour urinary total protein levels expressed as medians and percentiles (5th, 95th) for each trimester were as follows: 72.0 (28.4, 165.0), 88.0 (34.0, 185.0), and 108.0 (37.5, 258.0) mg in the first, second, and third trimesters, respectively. A significant increase in 24-hour urinary total protein excretion was observed throughout pregnancy (all P values <.001). Moreover, 24-hour urinary total protein levels were higher in the older (≥35 years) than in the younger (<35 years) group from mid-gestation. Specifically, the median (interquartile range) 24-hour urinary total protein levels by age were 72.2 (50.6-100.0) vs 70.5 (50.5-100.0) mg, 85.8 (62.0-117.0) vs 96.0 (68.0-127.8) mg, and 106.6 (76.0-146.2) vs 114.7 (81.5-153.6) mg in the first, second, and third trimesters, respectively. In addition, 24-hour proteinuria was significantly increased in higher-weight (overweight or obese) subgroups compared with lower-weight (underweight or normal-weight) subgroups (all P values <.05).

CONCLUSION

Our study provides reference values for 24-hour urinary total protein excretion with apparently uncomplicated pregnancies. Understanding these changes in low-risk pregnancies is essential for optimizing maternal management.

Impact of nicotine and maternal BMI on fetal birth weight

BACKGROUND

According to the World Health Organization, smoking is the most important risk factor for adverse pregnancy outcomes in industrialized nations. As the individual factors (body mass index - BMI (kg/m2) - and cigarette consumption) have been extensively investigated in pregnancy, we aimed to establish how maternal BMI and nicotine interact with regard to perinatal outcomes and birth weight.

METHODS

Data from 110.047 singleton pregnancies, achieved from the German Perinatal Survey in Schleswig-Holstein and registered between 2010 and 2017 were analyzed in August 2018 concerning maternal BMI and smoking. The BMI was taken from the maternity log. Information concerning the smoking status were self-reported and further subdivided into the following four categories: a) non-smokers; b) 1-7 cigarettes/day; c) 8-14 cigarettes/ day; and d) ≥ 15 cigarettes/ day. Furthermore, we classified women by their BMI into underweight, normal weight, overweight and obese. Comparisons between non-smokers and the respective smoking group, and their relationship with maternal BMI were performed by the t-test (birth weight). A P-value ≤0.05 was considered to indicate statistical significance.

RESULTS

A number of 97.092 women (88.2%) were non-smokers and 12.955 (11.8%) were smokers. Furthermore 10.3% of women of normal weight smoked during pregnancy, but both high and low BMI were associated with a high prevalence of smoking. The proportion of smokers was highest (18.1%) among underweight women (BMI ≤ 18.5 kg/m2). A large number of smokers (15.5%) were registered in the obesity group (BMI ≥ 30 kg/m2). Mean birth weight (≥ 37 + 0 gestational age) increased with increasing maternal BMI, and was reduced by smoking for every BMI category. The differences between smokers and non-smokers were always highly significant (p < 0.001). Mean birth weight varied between 2995 g in underweight frequent smokers and 3607 g in obese non-smokers.

CONCLUSION

Both maternal BMI and smoking during pregnancy influences the birth weight and therefore pregnancy outcome. Smoking during pregnancy was significantly associated with low birth weight. Pregnant women should be advised to cease or at least reduce smoking in order to improve the birth weight of the newborn and to minimize child morbidities.

Birth Size in Neonates with Congenital Adrenal Hyperplasia due to 21-hydroxylase Deficiency

OBJECTIVE

Classic congenital adrenal hyperplasia (CAH) secondary to 21-hydroxylase deficiency is characterized by increased prenatal adrenal androgen secretion. There are a small number of reports in the literature showing higher birth weight and length in CAH newborns.

METHODS

We analyzed birth weight and length data of 116 German newborns (48 boys, 68 girls) with classic CAH who were born during the period from 1990 to 2017. All children have been followed or are currently treated as outpatients in our clinic. All children were born at term. The mothers were healthy and their pregnancies were uneventful. The diagnosis of CAH was confirmed by molecular analyses of the CYP21A2 gene. Birth data were calculated as standard deviation (SD) scores according to German reference values.

RESULTS

Weight and length in male CAH newborns (mean ± SD) (3601±576 g; 52.4±2.85 cm) were significantly higher than in female CAH newborns (3347±442 g; 51.2±2.55 cm), but male-female differences in the CAH cohort were lost when the data were converted into SD scores. The birth sizes of the CAH newborns did not differ from the reference group. The birth sizes also did not differ between the different CAH genotypes. Maternal age, mode of delivery and maternal parity had no influence on birth size.

CONCLUSION

Our data show that prenatal hyperandrogenism does not affect fetal growth.

Somatic development at birth as influenced by maternal characteristics - an analysis of the German Perinatal Survey

We investigated the effects of maternal age, body weight, body height, weight gain during pregnancy, smoking during pregnancy, previous live births and being a single mother on somatic development at birth. We analysed data from the German Perinatal Survey for the years 1998-2000 from eight German federal states. We had available data on 508,926 singleton pregnancies and neonates in total; for 508,893 of which we could classify the neonates as small, appropriate or large for gestational age (SGA, AGA or LGA) based on the 10th and 90th birth weight percentiles. Multivariable regression analyses found statistically significant effects of a clinically relevant magnitude for smoking during pregnancy [odds ratio (OR) 2.9 for SGA births for women smoking >10 cigarettes per day], maternal height (OR 1.4 for SGA births for women <162 cm; OR 1.4 for LGA births for women >172 cm), maternal weight (OR 1.5 for SGA births for women <59 kg; OR 1.9 for LGA births for women >69 kg), weight gain during pregnancy (OR 1.9 for SGA births for women with a weight gain <8 kg; OR 2.0 for LGA births for women with a weight gain >18 kg) and previous live births (OR 2.1 for LGA births for women with one or more previous live births). Maternal age and being a single mother also had significant effects but their magnitude was small. Our analysis confirms the clinically relevant effects of smoking, maternal anthropometric measures and weight gain during pregnancy on neonatal somatic development.

Associations of maternal obesity and smoking status with perinatal outcomes

Maternal obesity and smoking are associated with adverse perinatal outcomes. These prevalent conditions contribute to health disparities. In this study, we examine whether maternal BMI moderates the impact of smoking cessation on short-term perinatal outcomes. This is a secondary analysis of assessments conducted from several prospective clinical trials examining the efficacy of incentives to promote smoking cessation during pregnancy. Participants were randomly assigned to receive financial incentives contingent upon smoking abstinence or a control condition. Pregnancy outcomes were abstracted from the medical record. ANCOVA and multiple logistic regression were used for statistical analysis. Among 388 women, there was a significant interaction between maternal pre-pregnancy BMI and smoking status on gestational age at delivery (p = .03) and admission to the NICU (p = .04). Among underweight/normal weight gravidas, smoking resulted in earlier deliveries and a greater likelihood of NICU admission than in those who abstained. Among overweight/obese gravidas, there was no effect of smoking on gestational age at delivery and infants of smokers were less likely to be admitted to the NICU. Maternal obesity and smoking have significant individual effects on perinatal outcome. Maternal overweight/obesity appears to moderate the effect of smoking on gestational age at delivery and on NICU admissions.

Contribution of overweight and obesity to adverse pregnancy outcomes among immigrant and non-immigrant women in Berlin, Germany

BACKGROUND

Maternal excessive weight and smoking are associated with an increased risk of pregnancy complications and adverse pregnancy outcomes. In Germany, immigrant women have a higher prevalence of pre-pregnancy overweight/obesity compared with autochthonous women. We compared the contribution of pre-pregnancy overweight/obesity to adverse pregnancy outcomes among immigrant and autochthonous women in Berlin/Germany.

METHODS

Data from 2586 immigrant women (from Turkey, Lebanon, other countries of origin) and 2676 autochthonous women delivering in three maternity hospitals of Berlin within 12 months (2011/2012) was used. Cox regression models were applied to estimate the association between overweight/obesity and smoking with the outcomes large-for-gestational-age (LGA), small-for-gestational-age (SGA), preterm birth (PTB) and extreme preterm-birth (E-PTB). Population attributive fractions (PAF) were calculated to quantify the proportion of the outcomes attributable to overweight/obesity and smoking, respectively.

RESULTS

Prevalence of overweight and obesity was 33.4% among autochthonous and 53.6% among Turkish women. Prevalence risk ratios of excessive weight were highest for LGA infants among immigrant and autochthonous women. The PAFs were -11.8% (SGA), +16.3% (LGA), +3.6% (PTB) and +16.5% (E-PTB) for the total study population.

CONCLUSIONS

Overweight/obesity is strongly associated with an increased risk of delivering an LGA infant among both immigrant and autochthonous women. Compared with autochthonous women, the contribution of excessive weight to LGA is even higher among immigrant women, in whom PAFs of overweight/obesity even exceed those of smoking for some outcomes.

Childhood growth trajectories according to combinations of pregestational weight status and maternal smoking during pregnancy: a multilevel analysis

Pregestational weight status and maternal smoking during pregnancy are significantly associated with fetal and childhood growth. However, few studies have examined associations between childhood growth and combinations of these factors using multilevel analysis. This study aimed to describe differences in childhood growth trajectories according to these combinations, using data from a prospective cohort study in Japan. The study participants were 1,973 women and their singletons, who were born between April 1, 1991 and March 31, 2003. Children were categorized according to whether they were born to normal-weight, nonsmoking mothers (NN); normal-weight, smoking mothers (NS); underweight, nonsmoking mothers (UN); underweight, smoking mothers (US); overweight, nonsmoking mothers (ON); or overweight, smoking mothers (OS). Birth weight and anthropometric data were collected from 1,965 children at birth (99.6%), 1,655 aged 3 (83.9%), 1,527 aged 5 (77.4%), 1,497 aged 7–8 (75.9%), and 1,501 aged 9–10 (76.1%). Multilevel analysis examining both individual and age as different level variables according to sex was used to describe the trajectories of body mass index z scores for statistical analyses. Although children of the OS group were the leanest at birth, their body mass indices had increased rapidly by 3 years of age. Moreover, body mass index was also likely to increase in boys in the NS and ON groups. A different trend was observed in girls. Body mass index decreased from 5 years of age in girls in the US group. There were no remarkable differences in body mass index trajectories between children in the other groups. In conclusion, childhood growth trajectories differed according to combinations of pregestational weight status and maternal smoking during pregnancy. Further, there were sex-related differences in the associations between childhood growth and factor combinations.

Analysis of the German Perinatal Survey of the Years 2007-2011 and Comparison with Data From 1995-1997: Maternal Characteristics

Background and Aim: We have previously presented analyses of data obtained from the German Perinatal Survey for the years 1995-1997. Here we present an analysis of data from the years 2007-2011 and compare the data to the previous data from the 1990s. Material and Methods: For the years 1995-1997, the data on 1 815 318 singleton pregnancies were provided by the Chambers of Physicians of all the states of Germany except Baden-Württemberg. For the years 2007-2011, the data on 3 187 920 singleton pregnancies from the German Perinatal Survey (all states of Germany) were obtained from the AQUA Institute in Göttingen, Germany. SPSS was used for data analysis. Plausibility checks were performed on the data. Results: Mean maternal age has increased over the years, from 28.7 years in 1995 to 30.2 years in 2011. We observed a decrease in smoking. While not all cases included data on maternal smoking after the pregnancy was known, when the cases with data on smoking were analysed, in 1995-1997 23.5 % of pregnant women were smokers compared to 11.2 % smokers in 2007-2011. Maternal body mass index (BMI) also changed; 8.2 % of women were obese (BMI: 30-40 kg/m²), while 13.0 % were obese in 2011. In 1995, 0.6 % of women were morbidly obese (BMI ≥ 40 kg/m²) compared to 1.8 % of women in 2011. The mean maternal body weight at the time of the first obstetric consultation also increased from 65.9 kg in 1995 to 68.7 kg in 2011. Conclusions: While the decrease in the number of women smoking over time is clearly a positive development, increasing maternal age and obesity present challenges in clinical practice.

The independent effects of second hand smoke exposure and maternal body mass index on the anthropometric measurements of the newborn

Background

Exposure to tobacco smoke during pregnancy, whether as active smoking or by exposure to secondhand smoke (SHS), is associated with adverse pregnancy outcomes including low birth weight (LBW) and small for gestational age infants due to the effect of tobacco on the anthropometric measurements of the newborn. This effect might be masked by maternal obesity as it increases fetal weight. The objectives of this study were to estimate the independent effects of maternal exposure to SHS and maternal body mass index (BMI) on the anthropometric measurements and on the prevalence of macrosomia and LBW among term infants.

Methods

Data were collected from women in the postnatal ward following delivery. Participants were stratified into six groups based on the BMI (underweight <18 kg/m², non-obese 18–29.9 kg/m², and obese ≥30 kg/m²) and the SHS exposure status (exposed and non- exposed), to examine the independent effects of BMI and SHS on infants’ anthropometry. Multiple regression analysis was used to explore the independent associations between the six groups and the risk of delivering a macrosomic or LBW infant.

Results

Infants of women exposed to SHS had significantly reduced anthropometric measurements compared to infants of unexposed women. The odds of delivering a macrosomic baby increased to 9-fold for women with BMI of ≥30 kg/m² compared to non-obese women; odds ratio (OR) 9.18, 95% Confidence Interval (CI) (1.01, 9.37); p = 0.04, this risk was attenuated to 1.5-fold in women exposed to SHS, OR 1.53, 95% CI (1.19, 12.1); p < 0.0001. The odds of delivering an LBW infant were more than doubled in underweight women compared to non-obese women, OR 2.15, 95% CI (1.001, 4.57); p = 0.034, and were further increased to almost 3-fold for women who were exposed to SHS, OR 2.71, 95% CI (1.82,4.045); p = 0.02.

Conclusion

Exposure to SHS was associated with reduced anthropometric measurements of the newborn and increased rate of LBW infants, irrespective of maternal BMI. Maternal obesity was associated with increased risk of delivering a macrosomic infant; conversely maternal underweight was associated with increased risk of delivering an LBW infant.

Relationships of risk factors for pre-eclampsia with patterns of occurrence of isolated gestational proteinuria during normal term pregnancy

BACKGROUND

Isolated gestational proteinuria may be part of the pre-eclampsia disease spectrum. Confirmation of its association with established pre-eclampsia risk factors and higher blood pressure in uncomplicated pregnancies would support this concept.

METHODS

Data from 11,651 women from the Avon Longitudinal Study of Parents and Children who had a term live birth but did not have pre-existing hypertension or diabetes or develop gestational diabetes or preeclampsia were used. Proteinuria was assessed repeatedly (median 12 measurements per woman) by dipstick and latent class analysis was used to identify subgroups of the population with different patterns of proteinuria in pregnancy.

RESULTS

Higher maternal pre-pregnancy body mass index (BMI), younger age, nulliparity and twin pregnancy were independently associated with increased odds of any proteinuria in pregnancy. Women who experienced proteinuria showed five patterns: proteinuria in early pregnancy only (≤ 20 weeks gestation), and onset at 21-28 weeks, 29-32 weeks, 33-36 weeks and ≥ 37 weeks gestation. There were higher odds of proteinuria onset after 33 weeks in obese women and after 37 weeks in nulliparous women compared with normal weight and multiparous women respectively. Smoking in pregnancy was weakly negatively associated with odds of proteinuria onset after 37 weeks. Twin pregnancies had higher odds of proteinuria onset from 29 weeks. In women with proteinuria onset after 33 weeks blood pressure was higher in early pregnancy and at the end of pregnancy.

CONCLUSIONS

Established pre-eclampsia risk factors were related to proteinuria occurrence in late gestation in healthy term pregnancies, supporting the hypothesis that isolated gestational proteinuria may represent an early manifestation of pre-eclampsia.

Somatic classification of neonates based on birth weight, length, and head circumference: quantification of the effects of maternal BMI and smoking

We defined neonates as small, appropriate, or large for gestational age (SGA, AGA, LGA) based on birth weight, length, and head circumference. We analyzed the effects on the somatic classification of maternal body mass index (BMI) (<18.5, 18.5-24.99, 25.0-29.99, ≥ 30) and smoking during pregnancy (0, 1-7, 8-14, ≥ 15 cigarettes daily). Data were from the German Perinatal Survey (1998-2000; 433,669 cases). The following refers to the classification by birth weight. In the normal maternal weight population SGA rates increased with cigarette consumption: 9.8%, 17.8%, 21.6%, and 25.4% for non-smokers, and smokers of 1-7, 8-14, and ≥ 15 cigarettes daily, respectively. In non-smoking underweight women the SGA rate was 17.4%. In underweight smokers of ≥ 15 cigarettes daily the SGA rate was 38.5% [odds ratio 5.77, 95% confidence interval 5.10-6.53, compared with normal weight non-smokers]. In the normal maternal weight population, LGA rates were 9.9%, 5.3%, 4.6%, and 3.5% for non-smokers, and smokers of 1-7, 8-14, and ≥ 15 cigarettes daily, respectively. In the obese, LGA rates were 20.9% (non-smokers) and 11.4% (≥ 15 cigarettes). Similar findings were obtained for the somatic classifications based on birth length and head circumference. Results for the various combinations of maternal BMI and smoking status in the three classification systems are described. Our findings may assist in individualized risk assessment for SGA and LGA births.