The effect of maternal hypertension on mortality in infants 22, 29weeks gestation

The impact of volume and neonatal level of care on outcomes of moderate and late preterm infants

OBJECTIVE

Evaluate the relationship of neonatal unit level of care (LOC) and volume with mortality or morbidity in moderate-late preterm (MLP) (32-36 weeks' gestation) infants.

DESIGN

Retrospective cohort study of 650,865 inborn MLP infants in 4976 hospitals-years using 2003-2015 linked administrative data from 4 states. Exposure was combined neonatal LOC and MLP annual volume. The primary outcome was death or morbidity (respiratory distress syndrome, severe intraventricular hemorrhage, necrotizing enterocolitis, sepsis, infection, pneumothorax, extreme length of stay) with components as secondary outcomes. Poisson regression models adjusted for patient characteristics with a random effect for unit were used.

RESULTS

In adjusted models, high-volume level 2 units had a lower risk of the primary outcome compared to low-volume level 3 units (aIRR 0.90 [95% CI 0.83-0.98] vs. aIRR 1.13 [95% CI 1.03-1.24], p < 0.001) CONCLUSION: MLP infants had improved outcomes in high-volume level 2 units compared to low-volume level 3 units in adjusted analysis.

Neonatal and Maternal Outcomes at 22-28 Weeks of Gestation by Mode of Delivery

OBJECTIVE

To compare neonatal and maternal outcomes after 22- to 28-week delivery between cesarean and vaginal delivery after stratification by gestational age and fetal presentation.

METHODS

This study was a repeated cross-sectional analysis using U.S. birth certificate data linked to infant death data from 2017 to 2020. We limited analyses to women with singleton pregnancies who gave birth at 22-28 weeks of gestation and whose neonates were admitted to the intensive care unit. Our primary outcome was neonatal death within 28 days. We also examined infant mortality within 1 year and severe maternal morbidity (SMM; any transfusion, unplanned hysterectomy, and intensive care unit admission). Outcomes were compared between cesarean and vaginal delivery after stratification by gestational age and fetal presentation. Multivariable logistic regression was performed to calculate adjusted odds ratios (vaginal delivery as a referent), controlling for potential confounders.

RESULTS

Of 69,672 individuals with eligible deliveries, 1,740 (2.5%) delivered at 22 weeks of gestation, 6,155 (8.8%) delivered at 23 weeks, 9,341 (13.4%) delivered at 24 weeks, 10,516 (15.1%) delivered at 25 weeks, 11,994 (17.2%) delivered at 26 weeks, 13,662 (19.6%) delivered at 27 weeks, and 16,264 (23.3%) delivered at 28 weeks. In cephalic fetuses, cesarean delivery compared with vaginal delivery was associated with neonatal death and infant mortality at 24 weeks of gestation and greater (not significant at 22-23 weeks) and SMM in all gestational age groups. In contrast, in noncephalic fetuses, cesarean delivery compared with vaginal delivery was associated with decreased odds of neonatal death and infant mortality in all gestational age groups. Sample size for SMM in noncephalic fetuses precluded multivariable modeling.

CONCLUSION

Cesarean delivery in cephalic fetuses was associated with increased odds of adverse neonatal outcomes (24 weeks of gestation or greater) and SMM (all gestational age groups). Cesarean delivery was associated with decreased odds of neonatal death compared with vaginal delivery for noncephalic fetuses in all gestational age groups.

County-Level Maternal Vulnerability and Preterm Birth in the US

Importance

Appreciation for the effects of neighborhood conditions and community factors on perinatal health is increasing. However, community-level indices specific to maternal health and associations with preterm birth (PTB) have not been assessed.

Objective

To examine the association of the Maternal Vulnerability Index (MVI), a novel county-level index designed to quantify maternal vulnerability to adverse health outcomes, with PTB.

Design, Setting, and Participants

This retrospective cohort study used US Vital Statistics data from January 1 to December 31, 2018. Participants included 3 659 099 singleton births at 22 plus 0/7 to 44 plus 6/7 weeks of gestation born in the US. Analyses were conducted from December 1, 2021, through March 31, 2023.

Exposure

The MVI, a composite measure of 43 area-level indicators, categorized into 6 themes reflecting physical, social, and health care landscapes. Overall MVI and theme were stratified by quintile (very low to very high) by maternal county of residence.

Main Outcomes and Measures

The primary outcome was PTB (gestational age <37 weeks). Secondary outcomes were PTB categories: extreme (gestational age ≤28 weeks), very (gestational age 29-31 weeks), moderate (gestational age 32-33 weeks), and late (gestational age 34-36 weeks). Multivariable logistic regression quantified associations of MVI, overall and by theme, with PTB, overall and by PTB category.

Results

Among 3 659 099 births, 298 847 (8.2%) were preterm (male, 51.1%; female, 48.9%). Maternal race and ethnicity included 0.8% American Indian or Alaska Native, 6.8% Asian or Pacific Islander, 23.6% Hispanic, 14.5% non-Hispanic Black, 52.1% non-Hispanic White, and 2.2% with more than 1 race. Compared with full-term births, MVI was higher for PTBs across all themes. Very high MVI was associated with increased PTB in unadjusted (odds ratio [OR], 1.50 [95% CI, 1.45-1.56]) and adjusted (OR, 1.07 [95% CI, 1.01-1.13]) analyses. In adjusted analyses of PTB categories, MVI had the largest association with extreme PTB (adjusted OR, 1.18 [95% CI, 1.07-1.29]). Higher MVI in the themes of physical health, mental health and substance abuse, and general health care remained associated with PTB overall in adjusted models. While the physical health and socioeconomic determinant themes were associated with extreme PTB, physical health, mental health and substance abuse, and general health care themes were associated with late PTB.

Conclusions and Relevance

The findings of this cohort study suggest that MVI was associated with PTB even after adjustment for individual-level confounders. The MVI is a useful measure for county-level PTB risk that may have policy implications for counties working to lower preterm rates and improve perinatal outcomes.

Outcomes of singleton preterm very low birth weight infants born to mothers with pregnancy-induced hypertension

The association between maternal pregnancy-induced hypertension (PIH) and neonatal mortality and morbidities in preterm infants has not been consistent. This study aimed to evaluate the influence of maternal PIH on mortality and morbidities in singleton infants with very low birth weight born before 30 weeks of gestational age using the Korean Neonatal Network (KNN) database. A total of 5340 singleton infants with very low birth weight were registered in the KNN registry, who were born at 23⁺⁰ to 29⁺⁶ weeks of gestational age between January 2015 and December 2020. Baseline characteristics and neonatal mortality and morbidities were compared between infants with PIH and non-PIH mothers. After adjustment for potential confounders, infants with PIH mothers had significantly higher odds of respiratory distress syndrome (OR 1.983; 95% CI 1.285-3.061, p = 0.002) and bronchopulmonary dysplasia (OR 1.458; 95% CI 1.190-1.785, p < 0.001), and severe bronchopulmonary dysplasia (OR 1.411; 95% CI 1.163-1.713, p < 0.001) than infants with non-PIH mothers, while there were no significant differences in severe intraventricular hemorrhage, periventricular leukomalacia, retinopathy of prematurity, or death during neonatal intensive care unit admission between infants with PIH and non-PIH mothers. This study showed that preterm infants with PIH mothers had an increased risk of neonatal respiratory morbidities, including respiratory distress syndrome and bronchopulmonary dysplasia.

Maternal hypertensive disorders and survival without major morbidities among extremely low gestation newborns

OBJECTIVE

Evaluate if odds of survival without major morbidity are higher among extremely low gestation neonates (ELGANs) born to mothers with chronic hypertension (cHTN) or hypertensive disorders of pregnancy (HDP) compared to ELGANs born to mothers without hypertension (HTN).

STUDY DESIGN

Retrospective study of prospectively collected data from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network. Included children had a birthweight of 401-1000 g and/or gestational age of 220/7 to 286/7 wks. The primary outcome was survival to discharge without major morbidity. Multivariable regression models were used to compare outcomes among ELGANs born to women with cHTN, HDP, and no HTN.

RESULTS

Survival without morbidities for newborns of mothers with no HTN, cHTN and HDP (29.1%, 32.9%, 37.0% respectively) did not differ after adjustment.

CONCLUSION

After adjusting for contributing variables maternal HTN is not associated with improved survival free of morbidity among ELGANs.

TRIALS REGISTRATION

clinicaltrials.gov Identifier: NCT00063063 (generic database).

Neonatal outcomes of twins &lt;29 weeks gestation of mothers with hypertensive disorders of pregnancy

BACKGROUND

Hypertensive disorders of pregnancy (HDP) are associated with dysfunctional placentation and are a major cause of maternal and neonatal morbidity and mortality. Twin pregnancies have a larger placental mass and are a risk factor for HDP. The effect of HDP on neonatal outcomes in twin pregnancies is unknown.

METHODS

Retrospective cohort study using the Canadian Neonatal Network database from 2010-2018 of twin infants &lt;29 weeks gestation born to mothers with HDP and normotensive pregnancies. Using multivariable models, we determined adjusted odds ratios (AORs) and 95% confidence intervals (CI) for mortality, bronchopulmonary dysplasia, severe neurologic injury, severe retinopathy of prematurity (ROP), necrotizing enterocolitis, and nosocomial infection in twin infants of mothers with HDP compared to twin infants of normotensive mothers.

RESULTS

Of the 2414 eligible twin infants &lt;29 weeks gestational age, 164 (6.8%) were born to mothers with HDP and had higher odds of severe ROP (AOR 2.48, 95% CI 1.34-4.59). Preterm twin infants born to mothers with HDP also had higher odds of mortality (AOR 2.02, 95% CI 1.23-3.32). There was no difference in other outcomes.

CONCLUSION

Preterm twin infants &lt;29 weeks gestation of HDP mothers have higher odds of severe ROP and mortality.

IMPACT

Hypertensive disorders of pregnancy, associated with placental dysfunction, are a major cause of maternal and neonatal morbidity and mortality. Twin pregnancy, associated with a larger placental mass, is a risk factor for hypertensive disorders of pregnancy. The effect of hypertensive disorders of pregnancy on outcomes of preterm twins is unknown. Preterm twins of mothers with hypertensive disorders of pregnancy are at higher risk of severe retinopathy of prematurity and mortality. Our data can be used to counsel parents and identify infants at higher risk of severe retinopathy of prematurity and mortality.

Medicaid and moms: the potential impact of extending medicaid coverage to mothers for 1 year after delivery

The American Rescue Plan provides a pathway for states to expand postpartum Medicaid coverage for low-income mothers through 12 months after delivery. Data suggests that extension of post-partum Medicaid coverage should improve access to outpatient health care services, increase healthcare utilization, improve chronic disease management for at-risk mothers, and reduce disparities in care for racial/ethnic groups over-represented in Medicaid. Opportunities to provide increased preventive care for perinatal mood disorders and smoking cessation also exist. Further, this policy may reduce the burden of late maternal mortality. While improved access to contraceptive service postpartum provides a potential mechanism by which birth outcomes may improve, the effect of this policy on NICU admission, low birth weight (LBW) infants, and preterm birth is unknown. We discuss possible birth, infant and maternal health outcomes which may result from this expansion, drawing on data from the 2010 Medicaid Expansion via the Affordable Care Act.

Association between maternal hypertensive disorders, fetal growth and childhood learning outcomes

OBJECTIVE

Both small for gestational age (SGA) birthweight and pregnancies complicated by maternal hypertension (HTN) are independently associated with poorer childhood learning outcomes, however the relative contribution of each remains unknown.

STUDY DESIGN

A retrospective cohort was created in which 2014-2017 third grade Rhode Island Department of Education data were linked to Rhode Island Department of Health birth certificate data. The study population was composed of non-anomalous, singleton births between 22- and 42-weeks' gestation. Reading and math proficiency were compared among four groups: 1) appropriate for gestational age (AGA) and no maternal HTN (referent), 2) AGA with HTN, 3) SGA without HTN and 4) SGA with HTN.

MAIN OUTCOME MEASURES

Bivariable and multivariable log-binomial regression were used to examine the association between subject proficiency and pregnancy complication, adjusting for potential confounders.

RESULTS

Of the 23,097 who met inclusion criteria, 1004 (4%) were AGA with HTN, 1575 (7%) were SGA without HTN and 176 (1%) were SGA with HTN. Overall, when adjusted for maternal age, gestational age, sex and socioeconomic factors, only children born SGA without HTN had reduced reading proficiency (relative risk (RR) 0.86 95% confidence interval (CI) 0.78, 0.92) and math proficiency (RR 0.88 95% CI 0.82, 0.94) compared to children born AGA without HTN.

CONCLUSION

In a diverse, statewide cohort, only SGA without HTN was associated with lower reading and math proficiency compared to uncomplicated pregnancies. This suggests that only decreased fetal growth from causes other than HTN is associated with risk of poorer school-age outcomes, and has implications for early resource allocation.

Maternal hypertension and survival in singletons and twins born at 23-29 weeks: not just one answer…

BACKGROUND

To describe the association between maternal hypertension (chronic and gestational, MH) and mortality in very preterm singletons and twins, focusing on how estimates depend on gestational age (GA) and size at birth.

METHODS

We estimated relative risks of in-hospital death in 12,320 singletons (MH: 22.4%) and 4381 twins (MH: 10.6%) born at 23-29 weeks in the Italian Neonatal Network (89 hospitals, 2008-2016).

RESULTS

Babies with MH had higher GA and were more frequently small-for-gestational age (SGA), especially singletons. In crude analyses, MH was associated with lower mortality in singletons. In multivariable analyses, the effects of GA and size differed between twins and singletons with and without MH. The best-fitting models included continuous birth weight (rather than SGA) and were stratified by GA. In these models, MH was associated with lower mortality in singletons-but not twins-born after week 25.

CONCLUSIONS

In this cohort of very preterm infants, the association between MH and mortality differed between singletons and twins and across strata of GA at birth. These estimates cannot be interpreted causally, but suggest that, from a descriptive/predictive standpoint, singletons with MH born after week 25 have lower mortality than singletons born to women without MH.

Neonatal respiratory outcomes in pregnancy induced hypertension: introducing a novel index

Objective: To evaluate short-term respiratory outcomes, mortality and bronchopulmonary dysplasia (BPD) in preterm infants born to mothers with and without pregnancy induced hypertension (PIH).Methods: Exposed infants <33 weeks' gestation were matched to controls in a 1:2 ratio, based on gestation, sex and antenatal steroid exposure in this retrospective cohort study. Primary outcomes were a novel cumulative respiratory index (cRI) (product of mean airway pressure-hours and FiO₂-hours while on invasive ventilation during first 72 hours), mortality and BPD.Results: Seventy-nine exposed infants were matched with 158 controls. cRI was higher in exposed infants (median 1854; IQR 186-13,901) versus controls (median 1359; IQR 210-11,302) but not statistically significant (p = .63). On conditional regression analysis, PIH did not predict cRI (adjusted β = 0.96; 95% CI = 0.79-1.17; p = .712). No association between PIH and mortality (unadjusted odds ratio [OR] = 3.14; 95% CI = 0.76-13.0; p=.11) was identified. PIH was significantly associated with BPD on univariate analysis (OR = 2.29; 95% CI = 1.02-5.17; p=.046), but not after adjustment (aOR = 1.26; 95% CI = 0.38-4.19; p=.7).Conclusions: PIH was not associated with cRI, mortality or BPD in this study. Further validation of cRI and exploration of its relationship with PIH as well as neonatal outcomes is warranted.

Pregnancy-induced hypertension and neonatal outcomes: a systematic review and meta-analysis

OBJECTIVE

Pregnancy-induced hypertension (PIH) is associated with preterm delivery but its independent impact on neonatal outcomes remains unclear. We sought to systematically review and meta-analyze clinical outcomes of preterm infants <37 weeks' gestation born to mothers with and without PIH.

STUDY DESIGN

Medline, Embase, PsychINFO and CINAHL were searched from January 2000 to October 2016. Studies with low-moderate risk of bias reporting neonatal outcomes based on PIH as primary exposure variable were included. Data were extracted independently by two co-authors.

RESULTS

PIH was associated with lower mortality (3 studies; adjusted odds ratio (aOR) 0.65; 95% confidence interval (CI) 0.54 to 0.79), lower severe retinopathy of prematurity (ROP) (2 studies; aOR 0.83; 0.72 to 0.96) and lower severe brain injury (2 studies; unadjusted OR (uOR) 0.57; 0.49 to 0.66). No association between PIH and short-term respiratory outcomes, bronchopulmonary dysplasia (BPD) or necrotizing enterocolitis (NEC) was identified. In subgroup analysis among infants <29 weeks' gestation, BPD odds were higher (3 studies; aOR 1.15; 1.06 to 1.26), whereas mortality lower (2 studies; aOR 0.73; 0.69 to 0.77). In subgroup analysis limited to severe PIH, odds of mortality (3 studies; uOR 2.36; 1.07 to 5.22) and invasive ventilation (3 studies; uOR 3.26; 1.11 to 9.61) were higher. In subgroup analysis limited to preeclampsia, odds of BPD (3 studies; uOR 1.21; 95% CI:1.03 to 1.43) and NEC were higher (3 studies; uOR 2.79; 95% CI:1.57 to 4.96).

CONCLUSION

PIH was associated with reduced odds of mortality and ROP (all infants), but higher odds for BPD (<29 weeks' gestation). The paradoxical reduction in mortality may be due to survival bias and deserves further exploration in future studies.

Antenatal Corticosteroid Prophylaxis in Singleton and Multiple Pregnancies

BACKGROUND

The effects of antenatal corticosteroids (ANS) in multiple pregnancies are disputed. In this article, we examined whether estimated effects differ in singletons and multiples and in small for gestational age (SGA) preterm infants.

METHODS

We studied 17 073 singletons (81% treated with ANS) and 8274 multiples (86% treated) born at 24-33 weeks from the Italian Neonatal Network (2005-2013). We used Poisson regression models with robust variance to estimate adjusted risk ratios (RR) of in-hospital death, severe intraventricular haemorrhage (IVH), periventricular leukomalacia (PVL), and the composite outcome of severe IVH and death.

RESULTS

Mortality was lower among ANS-treated vs. ANS-untreated infants, both in singletons (RR 0.63, 95% confidence interval (CI) 0.58, 0.68) and in multiples (RR 0.85, 95% CI 0.73, 0.98). IVH and the composite outcome of IVH and death, but not PVL, also occurred less frequently among ANS-treated infants. For these outcomes, the effect of ANS was stronger in singletons than in multiples (+35%, +32%, and +22% for death, IVH, and the composite outcome, respectively). Also among SGA infants, singletons, and multiples, ANS-treated infants had lower risk of death, IVH and of composite outcome than untreated ones.

CONCLUSIONS

In this large cohort of preterm infants, both multiples and singletons treated with ANS had a lower risk of mortality, of severe IVH, and of composite outcome of IVH and death, both in the overall sample and in SGA infants. Although ANS effect was weaker in multiples, our results support current recommendations to administer ANS prophylaxis in multiple pregnancies at risk of preterm delivery.

Matrix Metalloproteinases in Normal Pregnancy and Preeclampsia

Normal pregnancy is associated with marked hemodynamic and uterine changes that allow adequate uteroplacental blood flow and uterine expansion for the growing fetus. These pregnancy-associated changes involve significant uteroplacental and vascular remodeling. Matrix metalloproteinases (MMPs) are important regulators of vascular and uterine remodeling. Increases in MMP-2 and MMP-9 have been implicated in vasodilation, placentation, and uterine expansion during normal pregnancy. The increases in MMPs could be induced by the increased production of estrogen and progesterone during pregnancy. MMP expression/activity may be altered during complications of pregnancy. Decreased vascular MMP-2 and MMP-9 may lead to decreased vasodilation, increased vasoconstriction, hypertensive pregnancy, and preeclampsia. Abnormal expression of uteroplacental integrins, cytokines, and MMPs may lead to decreased maternal tolerance, apoptosis of invasive trophoblast cells, inadequate remodeling of spiral arteries, and reduced uterine perfusion pressure (RUPP). RUPP may cause imbalance between the antiangiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the proangiogenic vascular endothelial growth factor and placental growth factor, or stimulate the release of inflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors could target MMPs in the extracellular matrix as well as endothelial and vascular smooth muscle cells, causing generalized vascular dysfunction, increased vasoconstriction and hypertension in pregnancy. MMP activity can also be altered by endogenous tissue inhibitors of metalloproteinases (TIMPs) and changes in the MMP/TIMP ratio. In addition to their vascular effects, decreases in expression/activity of MMP-2 and MMP-9 in the uterus could impede uterine growth and expansion and lead to premature labor. Understanding the role of MMPs in uteroplacental and vascular remodeling and function could help design new approaches for prediction and management of preeclampsia and premature labor.

Mechanisms of Endothelial Dysfunction in Hypertensive Pregnancy and Preeclampsia

Preeclampsia is a pregnancy-related disorder characterized by hypertension and could lead to maternal and fetal morbidity and mortality. Although the causative factors and pathophysiological mechanisms are unclear, endothelial dysfunction is a major hallmark of preeclampsia. Clinical tests and experimental research have suggested that generalized endotheliosis in the systemic, renal, cerebral, and hepatic circulation could decrease endothelium-derived vasodilators such as nitric oxide, prostacyclin, and hyperpolarization factor and increase vasoconstrictors such as endothelin-1 and thromboxane A2, leading to increased vasoconstriction, hypertension, and other manifestation of preeclampsia. In search for the upstream mechanisms that could cause endothelial dysfunction, certain genetic, demographic, and environmental risk factors have been suggested to cause abnormal expression of uteroplacental integrins, cytokines, and matrix metalloproteinases, leading to decreased maternal tolerance, apoptosis of invasive trophoblast cells, inadequate spiral arteries remodeling, reduced uterine perfusion pressure (RUPP), and placental ischemia/hypoxia. RUPP may cause imbalance between the antiangiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the proangiogenic factors vascular endothelial growth factor and placental growth factor, or stimulate the release of other circulating bioactive factors such as inflammatory cytokines, hypoxia-inducible factor-1, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors could then target endothelial cells and cause generalized endothelial dysfunction. Therapeutic options are currently limited, but understanding the factors involved in endothelial dysfunction could help design new approaches for prediction and management of preeclampsia.