Maternal and neonatal outcomes of hospital vaginal deliveries in Tibet

Distinct methylomic signatures of high-altitude acclimatization and adaptation in the Tibetan Plateau

High altitude presents a challenging environment for human settlement. DNA methylation is an essential epigenetic mechanism that responds to environmental stimuli, but its roles in high-altitude short-term acclimatization (STA) and long-term adaptation (LTA) are poorly understood. Here, we conducted a methylome-wide association study involving 687 native highlanders and 299 acclimatized newcomers in the Tibetan Plateau and 462 native lowlanders to identify differentially methylated sites (DMSs) associated with STA or LTA. We identified 93 and 4070 DMSs for STA and LTA, respectively, which had no overlap, showed opposite asymmetric effect size patterns, and resided near genes enriched in distinct biological pathways/processes (e.g., cell cycle for STA and immune diseases and calcium signalling pathway for LTA). Epigenetic clock analysis revealed evidence of accelerated ageing in the acclimatized newcomers compared to the native lowlanders. Our research provides novel insights into epigenetic regulation in relation to high altitude and intervention strategies for altitude-related ageing or illnesses.

High-altitude residence alters blood-pressure course and increases hypertensive disorders of pregnancy

Objectives: To determine whether the full spectrum of hypertensive disorders of pregnancy (HDP) - comprising gestational hypertension; preeclampsia with or without severe features; eclampsia; and Hemolysis, Elevated Liver enzymes, and Low Platelets (HELLP) Syndrome - is increased at high (≥2500 m, 8250 ft) compared with lower altitudes in Colorado independent of maternal background characteristics, and if so their relationship to neonatal well-being.Methods: A retrospective cohort study was conducted using statewide birth-certificate data to compare the frequency of gestational hypertension, preeclampsia (with or without severe features), eclampsia, HELLP Syndrome, or all HDP combined in 617,958 Colorado women who lived at high vs. low altitude (<2500 m) and delivered during the 10-year period, 2007-2016. We also compared blood-pressure changes longitudinally during pregnancy and the frequency of HDP in 454 high (>2500 m)- vs. low (<1700 m)-altitude Colorado residents delivering in 2013 and 2014, and matched for maternal risk factors. Data were compared between altitudes using t-tests or chi-square, and by multiple or logistic regression analyses to adjust for risk factors and predict specific hypertensive or neonatal complications.Results: Statewide, high-altitude residence increased the frequency of each HDP disorder separately or all combined by 33%. High-altitude women studied longitudinally also had more HDP accompanied by higher blood pressures throughout pregnancy. The frequency of low birth weight infants (<2500 g), 5-min Apgar scores <7, and NICU admissions were also greater at high than low altitudes statewide, with the latter being accounted for by the increased incidence of HDP.Conclusions: Residence at high altitude constitutes a risk factor for HDP and recommends increased clinical surveillance. The increased incidence also makes high altitude a natural laboratory for evaluating the efficacy of predictive biomarkers or new therapies for HDP.

Sleep Disordered Breathing, a Novel, Modifiable Risk Factor for Hypertensive Disorders of Pregnancy

PURPOSE OF REVIEW

Pathophysiology of hypertensive disorders of pregnancy (HDP), especially preeclampsia, has not been fully elucidated. Most trials aimed at the prevention of preeclampsia have failed to show significant benefit and investigation of novel, modifiable risk factors is sorely needed. Sleep disordered breathing (SDB), a group of disorders for which treatments are available, meets these criteria. SDB impacts about a third of all pregnancies and is associated with hypertension in the general non-pregnant population.

RECENT FINDINGS

Recent studies have shown a high prevalence of SDB, especially in complicated pregnancies. Several studies have shown that pregnant women with SDB have a higher risk for developing HDP, and these two disorders are associated with similar maternal long-term cardiovascular outcomes. Based on limited animal models of gestational intermittent hypoxia and human studies, SDB and HDP share similar risk factors and some pathophysiological mechanisms. However, there is paucity of studies addressing causality of this association and identifying therapeutic targets for intervention. Maternal SDB represents a novel and modifiable risk factor of HDP. Further studies are needed in order to establish the exact mechanisms underlying this association and to identify specific areas for clinical interventions.

Uteroplacental Ischemia Is Associated with Increased PAPP-A2

Residence at high altitude (> 2500 m) has been associated with an increased frequency of preeclampsia. Pappalysin-2 (PAPP-A2) is an insulin-like growth factor binding protein-5 (IGFBP-5) protease that is elevated in preeclampsia, and up-regulated by hypoxia in placental explants. The relationships between PAPP-A2, altitude, and indices of uteroplacental ischemia are unknown. We aimed to evaluate the association of altitude, preeclampsia, and uterine artery flow or vascular resistance with PAPP-A2 levels. PAPP-A2, uterine artery diameter, volumetric blood flow, and pulsatility indices were measured longitudinally in normotensive Andean women residing at low or high altitudes in Bolivia and in a separate Andean high-altitude cohort with or without preeclampsia. PAPP-A2 levels increased with advancing gestation, with the rise tending to be greater at high compared to low altitude, and higher in early-onset preeclamptic compared to normotensive women at high altitude. Uterine artery blood flow was markedly lower and pulsatility index higher in early-onset preeclamptic normotensive women compared to normotensive women. PAPP-A2 was unrelated to uterine artery pulsatility index in normotensive women but positively correlated in the early-onset preeclampsia cases. We concluded that PAPP-A2 is elevated at high altitude and especially in cases of early-onset preeclampsia with Doppler indices of uteroplacental ischemia.

Human Genetic Adaptation to High Altitude: Evidence from the Andes

Whether Andean populations are genetically adapted to high altitudes has long been of interest. Initial studies focused on physiological changes in the O₂ transport system that occur with acclimatization in newcomers and their comparison with those of long-resident Andeans. These as well as more recent studies indicate that Andeans have somewhat larger lung volumes, narrower alveolar to arterial O₂ gradients, slightly less hypoxic pulmonary vasoconstrictor response, greater uterine artery blood flow during pregnancy, and increased cardiac O₂ utilization, which overall suggests greater efficiency of O₂ transfer and utilization. More recent single nucleotide polymorphism and whole-genome sequencing studies indicate that multiple gene regions have undergone recent positive selection in Andeans. These include genes involved in the regulation of vascular control, metabolic hemostasis, and erythropoiesis. However, fundamental questions remain regarding the functional links between these adaptive genomic signals and the unique physiological attributes of highland Andeans. Well-designed physiological and genome association studies are needed to address such questions. It will be especially important to incorporate the role of epigenetic processes (i.e.; non-sequence-based features of the genome) that are vital for transcriptional responses to hypoxia and are potentially heritable across generations. In short, further exploration of the interaction among genetic, epigenetic, and environmental factors in shaping patterns of adaptation to high altitude promises to improve the understanding of the mechanisms underlying human adaptive potential and clarify its implications for human health.

Maternal Health Behaviors and Outcomes in a Nomadic Tibetan Population

Introduction Despite significant global improvements in maternal health, large disparities persist. In China, rural women and women who live in western regions experience lower rates of maternal healthcare utilization and higher rates of maternal mortality than women elsewhere in the country. This paper examines maternal health care-seeking among nomadic Tibetan women in rural western China, a particularly understudied group. Methods Secondary data analysis was conducted with survey data collected in 2014 in Qinghai Province, China. Participants (rural, nomadic, adult women) provided birth histories and information on care received during antenatal, intrapartum and/or postpartum period(s). Using bivariate and multivariable logistic regression models, these outcomes were explored in relation to maternal characteristics (e.g., educational attainment and parity), use of health insurance, and time. Results Approximately half of all women had ever used antenatal care, institutional delivery, and/or skilled birth attendance. The utilization of these services has increased over time, from 10% of births prior to the year 2000, to approximately 50% since 2000. Utilization increased by year (odds ratios ranging from 1.1 to 1.3) even after controlling for covariates. Women with health insurance coverage were significantly more likely to use these services than women without insurance, although less than 20% of women reported that insurance paid for any antenatal and/or childbirth care. Discussion Utilization of maternal care is improving among this population but rates remain low in comparison to other women in rural, western China. Further targeted interventions may be needed to reach and adequately address the maternal health needs of this unique population.

Gestational Hypoxia and Developmental Plasticity

Hypoxia is one of the most common and severe challenges to the maintenance of homeostasis. Oxygen sensing is a property of all tissues, and the response to hypoxia is multidimensional involving complicated intracellular networks concerned with the transduction of hypoxia-induced responses. Of all the stresses to which the fetus and newborn infant are subjected, perhaps the most important and clinically relevant is that of hypoxia. Hypoxia during gestation impacts both the mother and fetal development through interactions with an individual's genetic traits acquired over multiple generations by natural selection and changes in gene expression patterns by altering the epigenetic code. Changes in the epigenome determine "genomic plasticity," i.e., the ability of genes to be differentially expressed according to environmental cues. The genomic plasticity defined by epigenomic mechanisms including DNA methylation, histone modifications, and noncoding RNAs during development is the mechanistic substrate for phenotypic programming that determines physiological response and risk for healthy or deleterious outcomes. This review explores the impact of gestational hypoxia on maternal health and fetal development, and epigenetic mechanisms of developmental plasticity with emphasis on the uteroplacental circulation, heart development, cerebral circulation, pulmonary development, and the hypothalamic-pituitary-adrenal axis and adipose tissue. The complex molecular and epigenetic interactions that may impact an individual's physiology and developmental programming of health and disease later in life are discussed.

Measuring high-altitude adaptation

High altitudes (>8,000 ft or 2,500 m) provide an experiment of nature for measuring adaptation and the physiological processes involved. Studies conducted over the past ~25 years in Andeans, Tibetans, and, less often, Ethiopians show varied but distinct O₂ transport traits from those of acclimatized newcomers, providing indirect evidence for genetic adaptation to high altitude. Short-term (acclimatization, developmental) and long-term (genetic) responses to high altitude exhibit a temporal gradient such that, although all influence O₂ content, the latter also improve O₂ delivery and metabolism. Much has been learned concerning the underlying physiological processes, but additional studies are needed on the regulation of blood flow and O₂ utilization. Direct evidence of genetic adaptation comes from single-nucleotide polymorphism (SNP)-based genome scans and whole genome sequencing studies that have identified gene regions acted upon by natural selection. Efforts have begun to understand the connections between the two with Andean studies on the genetic factors raising uterine blood flow, fetal growth, and susceptibility to Chronic Mountain Sickness and Tibetan studies on genes serving to lower hemoglobin and pulmonary arterial pressure. Critical for future studies will be the selection of phenotypes with demonstrable effects on reproductive success, the calculation of actual fitness costs, and greater inclusion of women among the subjects being studied. The well-characterized nature of the O₂ transport system, the presence of multiple long-resident populations, and relevance for understanding hypoxic disorders in all persons underscore the importance of understanding how evolutionary adaptation to high altitude has occurred.NEW & NOTEWORTHY Variation in O₂ transport characteristics among Andean, Tibetan, and, when available, Ethiopian high-altitude residents supports the existence of genetic adaptations that improve the distribution of blood flow to vital organs and the efficiency of O₂ utilization. Genome scans and whole genome sequencing studies implicate a broad range of gene regions. Future studies are needed using phenotypes of clear relevance for reproductive success for determining the mechanisms by which naturally selected genes are acting.

Exhaled nitric oxide is associated with postnatal adaptation to hypoxia in Tibetan and non-Tibetan newborn infants

AIM

This Chinese study assessed partial pressure of exhaled nitric oxide (PeNO) in healthy Tibetan and non-Tibetan newborn infants born at a very high altitude.

METHODS

Full-term Tibetan and non-Tibetan neonates born in Lhasa, 3658 metres above sea level, were compared to non-Tibetan neonates born in Kunming (1891 m) and Huai'an (16 m). The chemiluminiscence technique was used to measure the fraction of exhaled nitric oxide during spontaneous tidal breathing and this was then converted to partial pressure of exhaled nitric oxide (PeNO).

RESULTS

In their first week, Tibetan and non-Tibetan neonates born in Lhasa had persistently higher PeNO levels than non-Tibetan neonates born in Kunming and Huai'an, which was further verified by partial pressure of inspired oxygen adjustment. However, the non-Tibetans born in Lhasa required short-term oxygen therapy to improve their early postnatal oxygenation. The temporal changes of PeNO and cardio-respiratory function measurements demonstrated that Tibetan and non-Tibetan newborns in Lhasa initially needed to adapt to attain homoeostasis in oxygenation and gas exchange.

CONCLUSION

Tibetan and non-Tibetan newborn infants living at the same high altitude demonstrated comparable PeNO levels during postnatal adaptation to hypobaric hypoxia, which warrants further investigation of the mechanism of endogenous nitric oxide and hypoxic tolerance.

Uterine artery blood flow, fetal hypoxia and fetal growth

Evolutionary trade-offs required for bipedalism and brain expansion influence the pregnancy rise in uterine artery (UtA) blood flow and, in turn, reproductive success. We consider the importance of UtA blood flow by reviewing its determinants and presenting data from 191 normotensive (normal, n = 125) or hypertensive (preeclampsia (PE) or gestational hypertension (GH), n = 29) Andean residents of very high (4100-4300 m) or low altitude (400 m, n = 37). Prior studies show that UtA blood flow is reduced in pregnancies with intrauterine growth restriction (IUGR) but whether the IUGR is due to resultant fetal hypoxia is unclear. We found higher UtA blood flow and Doppler indices of fetal hypoxia in normotensive women at high versus low altitude but similar fetal growth. UtA blood flow was markedly lower in early-onset PE versus normal high-altitude women, and their fetuses more hypoxic as indicated by lower fetal heart rate, Doppler indices and greater IUGR. We concluded that, despite greater fetal hypoxia, fetal growth was well defended by higher UtA blood flows in normal Andeans at high altitude but when compounded by lower UtA blood flow in early-onset PE, exaggerated fetal hypoxia caused the fetus to respond by decreasing cardiac output and redistributing blood flow to help maintain brain development at the expense of growth elsewhere. We speculate that UtA blood flow is not only an important supply line but also a trigger for stimulating the metabolic and other processes regulating feto-placental metabolism and growth. Studies using the natural laboratory of high altitude are valuable for identifying the physiological and genetic mechanisms involved in human reproductive success.

Tibetan medicine: a unique heritage of person-centered medicine

With a history going back approximately 2,500 years, the Tibetan medicine, known as Sowa Rigpa in the Tibetan language, is one of the world’s oldest known traditional medicine. It originally developed during the pre-Buddhist era in the kingdom known as Shang Shung. As a traditional medicine, the future development of Tibetan medicine in Western countries is linked to being recognized as a popular and viable healthcare option providing an alternative clinical reality. Its inherent ability to incorparate predictive diagnostics, targeted prevention, and the creation of individualized medical treatment give Tibetan medicine great potential for assessing and treating patients.

High-end arteriolar resistance limits uterine artery blood flow and restricts fetal growth in preeclampsia and gestational hypertension at high altitude

The reduction in infant birth weight and increased frequency of preeclampsia (PE) in high-altitude residents have been attributed to greater placental hypoxia, smaller uterine artery (UA) diameter, and lower UA blood flow (Q(UA)). This cross-sectional case-control study determined UA, common iliac (CI), and external iliac (EI) arterial blood flow in Andeans residing at 3,600-4,100 m, who were either nonpregnant (NP, n = 23), or experiencing normotensive pregnancies (NORM; n = 155), preeclampsia (PE, n = 20), or gestational hypertension (GH, n = 12). Pregnancy enlarged UA diameter to ~0.62 cm in all groups, but indices of end-arteriolar vascular resistance were higher in PE or GH than in NORM. Q(UA) was lower in early-onset (≤34 wk) PE or GH than in NORM, but was normal in late-onset (>34 wk) illness. Left Q(UA) was consistently greater than right in NORM, but the pattern reversed in PE. Although Q(CI) and Q(EI) were higher in PE and GH than NORM, the fraction of Q(CI) distributed to the UA was reduced 2- to 3-fold. Women with early-onset PE delivered preterm, and 43% had stillborn small for gestational age (SGA) babies. Those with GH and late-onset PE delivered at term but had higher frequencies of SGA babies (GH=50%, PE=46% vs. NORM=15%, both P < 0.01). Birth weight was strongly associated with reduced Q(UA) (R(2) = 0.80, P < 0.01), as were disease severity and adverse fetal outcomes. We concluded that high end-arteriolar resistance, not smaller UA diameter, limited Q(UA) and restricted fetal growth in PE and GH. These are, to our knowledge, the first quantitative measurements of Q(UA) and pelvic blood flow in early- vs. late-onset PE in high-altitude residents.

Reducing intrapartum-related neonatal deaths in low- and middle-income countries-what works?

Each year, 814,000 neonatal deaths and 1.02 million stillbirths result from intrapartum-related causes, such as intrauterine hypoxia. Almost all of these deaths are in low- and middle-income countries, where women frequently lack access to quality perinatal care and may delay care-seeking. Approximately 60 million annual births occur outside of health facilities, and most of these childbirths are without a skilled birth attendant. Conditions that increase the risk of intrauterine hypoxia--such as pre-eclampsia/eclampsia, obstructed labor, and low birth weight--are often more prevalent in low resource settings. Intrapartum-related neonatal deaths can be averted by a range of interventions that prevent intrapartum complications (eg, prevention and management of pre-eclampsia), detect and manage intrapartum problems (eg, monitoring progress of labor with access to emergency obstetrical care), and identify and assist the nonbreathing newborn (eg, stimulation and bag-mask ventilation). Simple, affordable, and effective approaches are available for low-resource settings, including community-based strategies to increase skilled birth attendance, partograph use by frontline health workers linked to emergency obstetrical care services, task shifting to increase access to Cesarean delivery, and simplified neonatal resuscitation training (Helping Babies Breathe(SM)). Coverage of effective interventions is low, however, and many opportunities are missed to provide quality care within existing health systems. In sub-Saharan Africa, recent health services assessments found only 15% of hospitals equipped to provide basic neonatal resuscitation. In the short term, intrapartum-related neonatal deaths can be substantially reduced by improving the quality of services for all childbirths that occur in health facilities, identifying and addressing the missed opportunities to provide effective interventions to those who seek facility-based care. For example, providing neonatal resuscitation for 90% of deliveries currently taking place in health facilities would save more than 93,000 newborn lives each year. Longer-term strategies must address the gaps in coverage of institutional delivery, skilled birth attendance, and quality by strengthening health systems, increasing demand for care, and improving community-based services. Both short- and long-term strategies to reduce intrapartum-related mortality should focus on reducing inequities in coverage and quality of obstetrical and perinatal care.

Pregnancy and Village Outreach Tibet: a descriptive report of a community- and home-based maternal-newborn outreach program in rural Tibet

OBJECTIVE

The Pregnancy and Village Outreach Tibet (PAVOT) program, a model for community- and home-based maternal-newborn outreach in rural Tibet, is presented.

METHODS

This article describes PAVOT, including the history, structure, content, and activities of the program, as well as selected program outcome measures and demographic characteristics, health behaviors, and pregnancy outcomes of women who recently participated in the program.

RESULTS

The PAVOT program was developed to provide health-related services to pregnant rural Tibetan women at risk of having an unattended home birth. The program involves training local healthcare workers and laypersons to outreach pregnant women and family members. Outreach includes basic maternal-newborn health education and simple obstetric and neonatal life-saving skills training. In addition, the program distributes safe and clean birth kits, newborn hats, blankets, and maternal micronutrient supplements (eg, prenatal vitamins and minerals). More than 980 pregnant women received outreach during the study period. More than 92% of outreach recipients reported receiving safe pregnancy and birth education, clean birthing and uterine massage skills instruction, and clean umbilical cord care training. Nearly 80% reported basic newborn resuscitation skills training. Finally, nearly 100% of outreach recipients received maternal micronutrient supplements and safe and clean birth kits.

CONCLUSION

The PAVOT program is a model program that has been proven to successfully provide outreach to rural-living Tibetans by delivering maternal-newborn health education, skills training, and resources to the home.

Randomized double masked trial of Zhi Byed 11, a Tibetan traditional medicine, versus misoprostol to prevent postpartum hemorrhage in Lhasa, Tibet

The objective of this study was to compare a Tibetan traditional medicine (the uterotonic Zhi Byed 11 [ZB11]) to oral misoprostol for prophylaxis of postpartum hemorrhage (PPH). We conducted a double-blind randomized controlled trial at three hospitals in Lhasa, Tibet, People's Republic of China. Women (N = 967) were randomized to either ZB11 or misoprostol groups. Postpartum blood loss was measured in a calibrated blood collection drape. The primary combined outcome was incidence of PPH, defined as measured blood loss (MBL) > or = 500 mL, administration of open label uterotonics, or maternal death. We found that the rate of the combined outcome was lower among the misoprostol group (16.1% versus 21.8% for ZB11; P = .02). Frequency of PPH was lower with misoprostol (12.4% versus 17.4%; P = .02). There were no significant differences in MBL > 1000 mL or mean or median MBL. Fever was significantly more common in the misoprostol group (P = .03). The rate of combined outcome was significantly lower among women receiving misoprostol. However, other indices of obstetric hemorrhage were not significantly different.

Comparison of maternal and newborn outcomes of Tibetan and Han Chinese delivering in Lhasa, Tibet

AIM

To compare maternal and neonatal outcomes of Tibetan and Han Chinese women delivering vaginally at high altitude (3650 meters) in Lhasa, Tibet Autonomous Region, People's Republic of China.

METHOD

Comparative analysis of data from a prospective observational study of Tibetan (n = 938) and Han Chinese (n = 146) women delivering at three hospitals between January 2004 and May 2005.

RESULTS

Han Chinese women had higher rates of pre-eclampsia/gestational hypertension than Tibetan women, (10.3% vs 5.9%, P = 0.04). There was no difference in rates of postpartum hemorrhage between Tibetan and Han women (12.8% vs 17.1%, P = 0.15). Han newborns weighed significantly less than Tibetan newborns (P < 0.01), and were twice as likely to be small for gestational age, (24.5% vs 11.6%, P < 0.01). Tibetan newborns were less likely to have poor neonatal outcomes than Han newborns (P < 0.01).

CONCLUSION

In high altitude deliveries in Tibet, adverse outcomes were significantly more common among Han Chinese.