Smaller pelvic size in pregnant adolescents contributes to lower birth weight

The developmental impacts of natural selection on human pelvic morphology

Evolutionary responses to selection for bipedalism and childbirth have shaped the human pelvis, a structure that differs substantially from that in apes. Morphology related to these factors is present by birth, yet the developmental-genetic mechanisms governing pelvic shape remain largely unknown. Here, we pinpoint and characterize a key gestational window when human-specific pelvic morphology becomes recognizable, as the ilium and the entire pelvis acquire traits essential for human walking and birth. We next use functional genomics to molecularly characterize chondrocytes from different pelvic subelements during this window to reveal their developmental-genetic architectures. We then find notable evidence of ancient selection and genetic constraint on regulatory sequences involved in ilium expansion and growth, findings complemented by our phenotypic analyses showing that variation in iliac traits is reduced in humans compared to African apes. Our datasets provide important resources for musculoskeletal biology and begin to elucidate developmental mechanisms that shape human-specific morphology.

Associations of maternal age at marriage and pregnancy with infant undernutrition: Evidence from first‐time mothers in rural lowland Nepal

Objectives

Maternal factors shape the risk of infant undernutrition, however the contributions of age at marriage versus age at pregnancy are rarely disentangled. We explore these issues in a population from lowland rural Nepal, where median ages at marriage and first pregnancy are 15 and 17 years respectively and marriage almost always precedes pregnancy.

Methods

We analyzed data on first‐time mothers (n = 3002) from a cluster‐randomized trial (2012–2015). Exposures were ages at marriage and pregnancy, categorized into groups. Outcomes were z‐scores for weight (WAZ), length (LAZ), head circumference (HCAZ), and weight‐for‐length (WLZ), and prevalence of wasting and stunting, for neonates (<8 days) and infants (6–12 months). Mixed linear and logistic regression models tested associations of marriage and pregnancy ages with outcomes, adjusting for parental education, household assets, caste, landholding, seasonality, child sex, intervention arm, randomization strata and cluster.

Results

For neonates, pregnancy <18 years predicted lower LAZ, and <19 years predicted lower WAZ and HCAZ. Results were largely null for marriage age, however early pregnancy and marriage at 10–13 years independently predicted neonatal stunting. For infants, earlier pregnancy was associated with lower LAZ and HCAZ, with a trend to lower WAZ for marriage 10–13 years. Early pregnancy, but not early marriage, predicted infant stunting.

Conclusions

Early marriage and pregnancy were associated with poorer growth, mainly in terms of LAZ and HCAZ. Associations were stronger for neonatal than infant outcomes, suggesting pregnancy is more susceptible to these stresses. Early marriage and pregnancy may index different social and biological factors predicting child undernutrition.

Maternal physical, socioeconomic, and demographic characteristics and childbirth complications in rural lowland Nepal: Applying an evolutionary framework to understand the role of phenotypic plasticity

OBJECTIVES

Evolutionary perspectives on human childbirth have primarily focused on characteristics of our species in general, rather than variability within and between contemporary populations. We use an evolutionary framework to explore how physical and demographic characteristics of mothers shape the risks of childbirth complications in rural lowland Nepal, where childbearing typically commences in adolescence and chronic undernutrition is widespread, though maternal overweight is increasing in association with nutrition transition.

METHODS

We conducted secondary analyses of data from a cluster-randomized trial. Women aged 14-35 years were categorized by age, number of previous pregnancies, height, body mass index (BMI), husband's education, and household wealth. Multivariable logistic regression models tested whether these characteristics independently predicted risks of episiotomy and cesarean section (CS, n = 14 261), and obstructed labor (OL, n = 5185).

RESULTS

Risks were greatest among first-time adolescent mothers, though associations with age varied by outcome. Independent of age and parity, short stature and high BMI increased risks of CS and OL, whereas associations were weaker for episiotomy. Male offspring had increased risk of CS and OL but not episiotomy. Wealth was not associated with OL, but lower wealth and lower husband's education were associated with lower likelihood of episiotomy and CS.

CONCLUSIONS

At the individual level, the risk childbirth complications is shaped by trade-offs between fertility, growth, and survival. Some biological markers of disadvantage (early childbearing, short stature) increased the risk, whereas low socio-economic status was associated with lower risk, indicating reduced access to relevant facilities. Independent of these associations, maternal age showed complex effects.

The adverse maternal and perinatal outcomes of adolescent pregnancy: a cross sectional study in Hebei, China

Background

The adverse pregnancy outcomes caused by teenage pregnancy are major public health problems with significant social impact. While China is the most populous country in the world, and 8.5% of the women aged 10–50 years are adolescent women, we aimed to analyze the adverse maternal and perinatal outcomes of the adolescent pregnancy in Hebei Province, China.

Methods

There were 238,598 singleton pregnant women aged 10–34 years from January 1, 2013 to December 31, 2017 in the database of Hebei Province Maternal Near Miss Surveillance System (HBMNMSS). The 238,598 pregnant women were divided into two groups: adolescent group (aged 10–19 years) and adult group (aged 20–34 years). The adolescent group was divided into two subgroups (aged 10–17 years, aged 18–19 years), the adult group was divided into two subgroups (aged 20–24 years, aged 25–34 years). We compared the risk of adverse pregnancy outcomes using univariate and multivariate logistic regression. We also made a stratified analysis of nulliparous and multiparous adolescent pregnancy.

Results

Compared with women aged 20–34 years, women aged 10–19 years had lower risk of cesarean delivery [adjusted risk ratio (aRR): 0.75, 95% confidence interval (CI): 0.70–0.80], gestational diabetes mellitus (GDM) (aRR: 0.55, 95%CI: 0.41–0.73). Women aged 10–19 years had higher risk of preterm delivery (aRR: 1.76, 95%CI: 1.54–2.01), small for gestational age (SGA) (aRR: 1.19, 95%CI: 1.08–1.30), stillbirth (aRR: 2.58, 95%CI: 1.83–3.62), neonatal death (aRR: 2.63, 95%CI: 1.60–4.32). The adolescent women aged 10–17 years had significantly higher risk of stillbirth (aRR: 5.69, 95%CI: 3.36–9.65) and neonatal death (aRR: 7.57, 95%CI: 3.74–15.33) compared with the women aged 25–34 years. Younger adults (20–24 years) also had higher risks of preterm delivery (aRR: 1.26, 95%CI: 1.20–1.32), stillbirth (aRR: 1.45, 95%CI: 1.23–1.72), and neonatal death (aRR: 1.51, 95%CI: 1.21–1.90) compared with women aged 25–34 years. The structural equation model showed that preterm delivery and cesarean delivery had an indirect effect on neonatal death in adolescent pregnancy.

Conclusions

The adolescent pregnancy was related to adverse perinatal (fetal and neonatal) outcomes, such as preterm delivery, stillbirth and neonatal death, especially in younger adolescent pregnancies.

The impact of maternal age on foetal growth patterns and newborn size

The association patterns between maternal age and foetal growth parameters as well as newborn size were analysed using a dataset of 4737 singleton term births taking place at the Viennese Danube hospital. Foetal growth patterns were reconstructed by the results of three ultrasound examinations carried out at the 11th/12th, 20th/21th and 32th/33thweek of gestation. In detail, crown-rump length, biparietal diameter, fronto-occipital diameter, head circumference, abdominal transverse diameter, abdominal anterior-posterior diameter, abdominal circumference, and femur length were determined. Birth weight, birth length and head circumference were measured immediately after birth. Young teenage mothers (≤15 years), older adolescent mothers (16-19 years), mothers of optimal age range (20-35 years) and mothers of advanced age (>35 years) differed significantly in body height, pre-pregnancy weight status and gestational weight gain. Surprisingly, the foetuses of young adolescent mothers were the largest ones during first trimester. During the second and third trimester however, the foetuses of mothers of optimal age range (20-35 years) and mothers older than 35 years showed larger biometric dimensions than adolescent mothers. According to multiple regression analyses, maternal age was significantly related to Foetal head size (ß =-0.04; 95% CI = -0,08 – 0.01; p=0.034) and abdominal dimensions (ß= 0.03; 95% CI = 0.01-0.05; p=0,011) during the second trimester and to birthweight (ß= -0.03; 95% CI= -4.40 – 0.04; p=0.050). The associations however, are quite weak and the statistical significance is maybe due to the large sample size. At the time of birth, offspring of mothers of optimal age range (20 to 35 years) is significantly larger than that of adolescent mothers and mothers of advanced age. Mothers of advanced age showed the significantly highest (p=<0.0001) prevalence (5.6%) of SGA newborns (<2500g). The small size of newborn among young adolescent mothers may be due to a competition over nutrients between the still growing mothers and the foetuses during the third trimester, while placental ageing may be responsible for smaller size of offspring among mothers of advanced age.

Maternal pelvic dimensions and neonatal size: Implications for growth plasticity in early life as adaptation

Patterns of fetal growth predict non-communicable disease risk in adult life, but fetal growth variability appears to have a relatively weak association with maternal nutritional dynamics during pregnancy. This challenges the interpretation of fetal growth variability as 'adaptation'. We hypothesized that associations of maternal size and nutritional status with neonatal size are mediated by the dimensions of the maternal pelvis. We analysed data on maternal height, body mass index (BMI) and pelvic dimensions (conjugate, inter-spinous and inter-cristal diameters) and neonatal gestational age, weight, length, thorax girth and head girth (n = 224). Multiple regression analysis was used to identify independent maternal predictors of neonatal size, and the mediating role of neonatal head girth in these associations. Pelvic dimensions displaced maternal BMI as a predictor of birth weight, explaining 11.6% of the variance. Maternal conjugate and inter-spinous diameters predicted neonatal length, thorax girth and head girth, whereas inter-cristal diameter only predicted neonatal length. Associations of pelvic dimensions with birth length, but not birth weight, were mediated by neonatal head girth. Pelvic dimensions predicted neonatal size better than maternal BMI, and these associations were mostly independent of maternal height. Sensitivity of fetal growth to pelvic dimensions reduces the risk of cephalo-pelvic disproportion, potentially a strong selective pressure during secular trends in height. Selection on fetal adaptation to relatively inflexible components of maternal phenotype, rather than directly to external ecological conditions, may help explain high levels of growth plasticity during late fetal life and early infancy.

Factors influencing utilisation of maternal health services by adolescent mothers in Low-and middle-income countries: a systematic review

BACKGROUND

Adolescent mothers aged 15-19 years are known to have greater risks of maternal morbidity and mortality compared with women aged 20-24 years, mostly due to their unique biological, sociological and economic status. Nowhere Is the burden of disease greater than in low-and middle-income countries (LMICs). Understanding factors that influence adolescent utilisation of essential maternal health services (MHS) would be critical in improving their outcomes.

METHODS

We systematically reviewed the literature for articles published until December 2015 to understand how adolescent MHS utilisation has been assessed in LMICs and factors affecting service utilisation by adolescent mothers. Following data extraction, we reported on the geographical distribution and characteristics of the included studies and used thematic summaries to summarise our key findings across three key themes: factors affecting MHS utilisation considered by researcher(s), factors assessed as statistically significant, and other findings on MHS utilisation.

RESULTS

Our findings show that there has been minimal research in this study area. 14 studies, adjudged as medium to high quality met our inclusion criteria. Studies have been published in many LMICs, with the first published in 2006. Thirteen studies used secondary data for assessment, data which was more than 5 years old at time of analysis. Ten studies included only married adolescent mothers. While factors such as wealth quintile, media exposure and rural/urban residence were commonly adjudged as significant, education of the adolescent mother and her partner were the commonest significant factors that influenced MHS utilisation. Use of antenatal care also predicted use of skilled birth attendance and use of both predicted use of postnatal care. However, there may be some context-specific factors that need to be considered.

CONCLUSIONS

Our findings strengthen the need to lay emphasis on improving girl child education and removing financial barriers to their access to MHS. Opportunities that have adolescents engaging with health providers also need to be seized. These will be critical in improving adolescent MHS utilisation. However, policy and programmatic choices need to be based on recent, relevant and robust datasets. Innovative approaches that leverage new media to generate context-specific dis-aggregated data may provide a way forward.

Utilisation of maternal health services by adolescent mothers in Kenya: analysis of the demographic health survey 2008-2009

BACKGROUND

Many Kenyan adolescents die following pregnancy and childbirth complications. Maternal health services (MHS) utilisation is key to averting such poor outcomes. Our objectives were to understand the characteristics of adolescent mothers in Kenya, describe their MHS utilisation pattern and explore factors that influence this pattern.

METHODS

We collected demographic and MHS utilisation data of all 301 adolescent mothers aged 15-19 years included in the Kenya Demographic Health Survey 2008/2009 (KDHS). Descriptive statistics were used to characterise them and their MHS utilisation patterns. Bivariate and multivariate analyses were used to test associations between selected predictor variables and MHS utilisation.

FINDINGS

Eighty-six percent, 48% and 86% of adolescent mothers used ante-natal care (ANC), skilled birth attendance (SBA) and post-natal care (PNC), respectively. Adolescent mothers from the richest quintile were nine (CI=2.00-81.24, p=0.001) and seven (CI=3.22-16.22, p<0.001) times more likely to use ANC and SBA, respectively, compared to those from the poorest. Those with primary education were four (CI=1.68-9.64, p<0.001) and two (CI=0.97-4.81, p=0.043) times more likely to receive ANC and SBA, respectively, compared to uneducated mothers, with similar significant findings amongst their partners. Urban adolescent mothers were six (CI=1.89-32.45, p=0.001) and four (CI=2.00-6.20, p<0.001) times more likely to use ANC and SBA, respectively, compared to their rural counterparts. The odds of Maasai adolescent mothers using ANC was 90% (CI=0.02-0.93, p=0.010) lower than that of Kalenjin mothers.

CONCLUSIONS

Adolescent MHS utilisation in Kenya is an inequality issue. To address this, focus should be on the poorest, least educated, rural-dwelling adolescent mothers living in the most disadvantaged communities.