Effect of gender on blood pressure levels of very low birthweight infants in the first 48 hours of life

Impact of sex, race, and social determinants of health on neonatal outcomes

Despite the global improvements in neonatal outcomes, mortality and morbidity rates among preterm infants are still unacceptably high. Therefore, it is crucial to thoroughly analyze the factors that affect these outcomes, including sex, race, and social determinants of health. By comprehending the influence of these factors, we can work towards reducing their impact and enhancing the quality of neonatal care. This review will summarize the available evidence on sex differences, racial differences, and social determinants of health related to neonates. This review will discuss sex differences in neonatal outcomes in part I and racial differences with social determinants of health in part II. Research has shown that sex differences begin to manifest in the early part of the pregnancy. Hence, we will explore this topic under two main categories: (1) Antenatal and (2) Postnatal sex differences. We will also discuss long-term outcome differences wherever the evidence is available. Multiple factors determine health outcomes during pregnancy and the newborn period. Apart from the genetic, biological, and sex-based differences that influence fetal and neonatal outcomes, racial and social factors influence the health and well-being of developing humans. Race categorizes humans based on shared physical or social qualities into groups generally considered distinct within a given society. Social determinants of health (SDOH) are the non-medical factors that influence health outcomes. These factors can include a person's living conditions, access to healthy food, education, employment status, income level, and social support. Understanding these factors is essential in developing strategies to improve overall health outcomes in communities.

Neonatal Blood Pressure Standards: What Is "Normal"?

Blood pressure (BP) is routinely measured in newborn infants. Published BP nomograms demonstrate a rise in BP following delivery in healthy infants at all gestational ages (GA) and evidence that BP values are higher with increasing birth weight and GA. However, the complex physiology that occurs in newborn infants and range of BP values observed at all GA make it difficult to identify "normal" BP for a specific infant at a specific time under specific conditions. As such, complete hemodynamic assessment should include the physical examination, perinatal history, other vital signs, and laboratory values in addition to BP values.

Gender disparities in preterm neonatal outcomes

AIM

From birth to old age, males generally have poorer disease outcomes compared to females. Preterm infants display a marked gender disparity in disease outcomes, and the underlying mechanisms are not well delineated. Our aim was to review the literature on clinical outcomes between preterm infants of different genders and discuss the potential mechanisms underlying the differences observed.

METHODS

A literature review was undertaken for experimental and clinical research related to gender differences in preterm outcomes.

RESULTS

Preterm male infants appear to have consistently worse outcomes compared to females, and the aetiology of these differences, while mostly undetermined, is likely multifactorial.

CONCLUSION

The male disadvantage in preterm outcomes is likely multifactorial with hormonal, genetic and immunological differences likely playing key roles. Gender is an important variable in preterm outcome and should be considered when designing clinical and experimental research.

Delivery room blood pressure percentiles of healthy, singleton, liveborn neonates

BACKGROUND

Arterial blood pressure (BP) is one of the four vital signs that reflect cardiovascular status in neonates. The present study aimed to obtain BP percentiles among healthy, singleton, liveborn neonates between 34 and 43 weeks of gestation who were less than 1 h old.

METHODS

BP measurements were taken after birth in supine-positioned neonates in the delivery room using an oscillometric device. A total of 982 well-nourished neonates who did not require resuscitation, were not fetally malnourished, were not admitted to the neonatal intensive care unit and were without obvious congenital abnormalities were included in the study.

RESULTS

Sex- and type-of-delivery-specific 5th and 95th percentiles BP measurements were obtained for gestation. Mean BP values for systolic, diastolic and mean of term neonates were 63.98 ± 12.29 mmHg, 38.34 ± 11.06 mmHg and 49.32 ± 11.33 mmHg, and late preterm neonates were 61.80 ± 12.46 mmHg, 33.17 ± 9.97 mmHg and 46.52 ± 10.8 mmHg, respectively. There were weak but significant correlations between birthweight, birth length and head circumference and systolic, diastolic and mean arterial BP values (r = 0.20, r = 0.15 and r = 0.20, respectively, P < 0.001). Neonates who were delivered vaginally had higher mean BP values for systolic, diastolic and mean than neonates delivered by cesarean section (P < 0.05). Female neonates had higher systolic BP values than male neonates (P < 0.05).

CONCLUSION

Data presented in this study include sex- and delivery-mode-specific BP percentile curves using an oscillometric method and serve as a valuable reference for physicians in dealing with the management of singleton, liveborn late preterm and term newborns in the delivery room intensive care.

Analysis of the evidence for the lower limit of systolic and mean arterial pressure in children

OBJECTIVE

Systolic blood pressure (SBP) and mean arterial pressure (MAP) are essential evaluation elements in ill children, but there is wide variation among different sources defining systolic hypotension in children, and there are no normal reference values for MAP. Our goal was to calculate the 5th percentile SBP and MAP values in children from recently updated data published by the task force working group of the National High Blood Pressure Education Program and compare these values with the lowest limit of acceptable SBP and MAP defined by different sources.

DESIGN

Mathematical analysis of clinical database.

METHODS

The 50th and 95th percentile SBP values from task force data were used to derive the 5th percentile value for children from 1 to 17 yrs of age stratified by height percentiles. MAP values were calculated using a standard mathematical formula. Calculated SBP values were compared with systolic hypotension definitions from other sources. Linear regression analysis was applied to create simple formulas to estimate 5th percentile SBP and 5th and 50th percentile MAP for different age groups at the 50th height percentile.

RESULTS

A 9-21% range in both SBP and MAP values was noted for different height percentiles in the same age groups. The 5th percentile SBP values used to define hypotension by different sources are higher than our calculated values in children but are lower than our calculated values in adolescents. Clinical formulas for calculation of SBP and MAP (mm Hg) in normal children are as follows: SBP (5th percentile at 50th height percentile) = 2 x age in years + 65, MAP (5th percentile at 50th height percentile) = 1.5 x age in years + 40, and MAP (50th percentile at 50th height percentile) = 1.5 x age in years + 55.

CONCLUSION

We developed new estimates for values of 5th percentile SBP and created a table of normal MAP values for reference. SBP is significantly affected by height, which has not been considered previously. Although the estimated lower limits of SBP are lower than currently used to define hypotension, these values are derived from normal healthy children and are likely not appropriate for critically ill children. Our data suggest that the current values for hypotension are not evidence-based and may need to be adjusted for patient height and, most important, for clinical condition. Specifically, we suggest that the definition of hypotension derived from normal children should not be used to define the SBP goal; a higher target SBP is likely appropriate in many critically ill and injured children. Further studies are needed to evaluate the appropriate threshold values of SBP for determining hypotension.

Blood pressure disorders in the neonate: hypotension and hypertension

Although many sick newborns are treated for hypotension and hypertension, the normal physiologic blood pressure range ensuring appropriate organ perfusion is uncertain. Treatment decisions are based on statistically defined gestational and postnatal age-dependent normative blood-pressure values, combined with clinical intuition, because of difficulties evaluating organ perfusion and adequacy of cerebral oxygen delivery. Early-onset hypotension usually results from the combined effects of abnormal peripheral vasoregulation, myocardial dysfunction, and hypovolemia. Volume administration is the primary initial therapy but its use can be associated with significant untoward effects, especially in preterm infants, and should be limited to 10-20 mL/kg of isotonic saline. If the blood pressure cannot be normalized, dopamine should be added, and sometimes followed by adrenaline (epinephrine) and corticosteroids. Hypertension, most often caused by congenital or acquired renovascular disease or volume overload, needs a thorough search for the etiology and cautious treatment, so that blood pressure does not fall too quickly or too low.

Systolic blood pressure in babies of less than 32 weeks gestation in the first year of life. Northern Neonatal Nursing Initiative

AIM

To define the normal range of systolic blood pressure in a non-selective population based sample of babies of low gestation throughout early infancy.

METHODS

Daily measurements of systolic blood pressure were made in all the babies of less than 32 weeks gestation born in the North of England in 1990 and 1991 during the first 10 days of life. Additional measurements were obtained from 135 of these babies throughout the first year of life. Systolic pressure was measured by sensing arterial flow with a Doppler ultrasound probe. It was assumed that blood pressure had never been pathologically abnormal in the neonatal period if the child was alive and free from severe disability two years later. Data of adequate quality were available from 398 such children. Additional data wer collected, for comparative purposes, from 123 babies of 32, 36, or 40 weeks of gestation.

RESULTS

Systolic pressure correlated with weight and gestation at birth, and rose progressively during the first 10 days of life. The coefficient of variation did not vary with gestational or postnatal age (mean value 17%), the relation with gestation being closer than with birthweight. Systolic pressure rose 20% during the first 10 days from an initial mean of 42 mm Hg in babies of 24 weeks gestation, and by 42% from an initial mean of 48 mm Hg in babies of 31 weeks gestation. These findings were not altered by the exclusion of data from 14 babies who had inotropic support during this time. Simultaneous measurements in three centres using an oscillometric technique revealed that this technique tended to overestimate systolic pressure when this was below average. Systolic pressure finally stabilised at a mean of 92 (95% CI 72-112) mm Hg at a postconceptional age of 44-48 weeks irrespective of gestation at birth.

CONCLUSION

Systolic blood pressure 4-24 hours after birth was less than gestational age (in weeks) in only 3% of non-disabled long term survivors. Systolic pressure rose with increasing gestation and increasing postnatal age, but stabilised some six weeks after term, regardless of gestation at birth.

Blood pressure ranges in premature infants. I. The first hours of life

We studied blood pressure in the first hours of life in a cohort of 1105 preterm infants weighing 501 to 2000 gm; these infants represented 83% of all births at these weights that resulted in admission to three intensive care nurseries during a 34-month period between 1984 and 1987. To assess the effects of specific risk factors, we identified 244 healthy infants, 164 infants who received mechanical ventilation but had no other conditions, 47 infants whose only risk factor was the presence of hypertension or preeclampsia in the mother, and 86 infants with depressed Apgar scores regardless of the presence of the other conditions. We documented each infant's minimum and maximum systolic (Smin, Smax) and diastolic (Dmin, Dmax) pressures during the first 3 to 6 hours of life. In the healthy group, Smin was 47 mmHg; Smax, 59 mmHg; Dmin, 24 mmHg; and Dmax, 35 mmHg. In the ventilation group, Smin was 41 mmHg; Smax, 57 mmHg; Dmin, 22 mmHg; and Dmax, 35 mmHg. The Smin and Dmin values were both significantly lower in infants who received mechanical ventilation than in healthy infants (p < 0.01). In the maternal hypertension group, Smin was 49 mmHg; Smax, 59 mmHg; Dmin, 25 mmHg; and Dmax, 34 mmHg. Only the Smin value was significantly higher than in healthy infants. In the group with low Apgar scores, Smin was 33 mmHg; Smax, 51 mmHg; Dmin, 19 Hg; and Dmax, 34 mmHg. Thus all these values were significantly lower than in all the other groups (p < 0.05). Of infants with low Apgar scores, 20% to 50% had values below the 5th percentile for healthy infants. Birth weight and gestational age correlated with blood pressure limits only in the infants with low Apgar scores. We conclude that in healthy premature infants the limits of systolic and diastolic blood pressure are independent of birth weight and gestational age. Infants with low Apgar scores tend to have lower pressures, and infants whose mothers have hypertension have higher pressures than infants in the healthy cohort.

Effect of chronic lung disease on blood pressure levels at follow up

Thirteen preterm infants (median gestational age 28 weeks) who had developed neonatal chronic lung disease (CLD) and 13 gender- and gestational age-matched controls (without CLD) were prospectively followed. The infants were seen at monthly intervals for 6 months. At each attendance the infants were examined and their blood pressure (BP) measured using a noninvasive Doppler technique. No infant developed symptoms related to hypertension and there were no significant differences in their BP levels at follow up. Our results suggests significant BP elevation is uncommon following neonatal CLD.