Fetal response to induced maternal stress

BACKGROUND: Despite increased attention to the role of antenatal maternal psychological stress in postnatal development, remarkably little information is available on the nature of the intrauterine fetal response to maternal psychological state. AIMS: To determine whether: (1) the fetus responds to maternal stress; (2) the fetal response changes over gestation; and (3) individual maternal and fetal response patterns are stable over time. STUDY DESIGN: Induced maternal stress at 24 and 36 weeks gestational age using the Stroop color-word task. SUBJECTS: 137 low-risk pregnant women with normally developing fetuses. OUTCOME MEASURES: Maternal (heart rate and skin conductance) and fetal (heart rate, heart rate variability, and motor activity) responses. RESULTS: The manipulation evoked maternal sympathetic activation, which declined in magnitude from 24 to 36 weeks gestation. Fetuses responded to the manipulation with increased variability in heart rate (F(2,256)=7.80, p<0.001) and suppression of motor activity (F(2,216)=15.47, p<0.001). The magnitude of the fetal response increased over gestation. The degree of maternal reactivity to and recovery from the stressor were correlated over time (r's=0.53 and 0.60 for heart rate; r's=0.31 and 0.36 for skin conductance; p's<0.001). There was moderate stability in the magnitude of the fetal motor response (r=0.25, p<0.01). CONCLUSIONS: Demonstration of fetal responses to maternal sympathetic activation evoked by a benign cognitive stressor suggests that fetal neurobehavioral regulation is routinely disrupted by maternal environmental intrusions. There is no evidence of a protective effect of diminished maternal sensitivity to stress on the fetus. Individual stability in the magnitude of the evoked maternal physiologic and psychological responses from 24 to 36 weeks and stability in the fetal motor response implies that characteristic response patterns emerge in utero. We propose that autonomic development is partially entrained through these processes.     

Fetal state concordance predicts infant state regulation

Fetal state organization reflects the development of the central nervous system but may also portend individual differences in postnatal state organization. The goal of the present study was to determine the extent to which fetal state regulation, defined as the percentage of an observation period in which fetal heart rate and movement concordance was displayed, is associated with neonatal state regulation. Neonatal state regulation was evaluated through a standard neurobehavioral assessment at 2 weeks postpartum. Biobehavioral concordance was measured in 52 normally developing fetuses at 24, 30 and 36 weeks gestation using an actocardiograph; the neonatal assessment was administered to 41 of these as infants. Intrafetal stability in biobehavioral concordance did not emerge prior to 36 weeks. Fetuses with higher concordance at 36 weeks were infants that displayed better state regulation during the exam, including more alertness and orientation (r(35)=0.29), less cost of maintaining attention (r=0.36), less irritability (r=-0.41), better regulatory capacity (r=0.47), a greater range of available states (r=0.34), and were significantly more likely to maintain control during the most aversive portions of the exam F(1,31)=4.63, p<0.05). These results support fetal state as a stable individual attribute that is conserved across the prenatal and neonatal periods.     

Prior pain induces heightened motor responses during clustered care in preterm infants in the NICU

BACKGROUND: Acute pain is a significant stressor for preterm infants in neonatal intensive care units (NICU); however, little is known about the effects of acute pain on subsequent motor responses during clusters of tactile handling. AIMS: (1) To compare facial, body and heart rate reactivity in preterm infants at 32 weeks gestational age (GA) during routine care-giving tasks following a rest period (RCC: diapering, measuring abdominal girth and axillary temperature, mouth care) with their responses to Clustered Care following blood collection (PCC). (2) To examine how GA at birth affects patterns of stress and self-regulatory behaviors during RCC and PCC. STUDY DESIGN: Within-group crossover design (random order). SUBJECTS: Preterm infants, N=54 (mean GA at birth 29.3 +/- 2.2 weeks; mean birth weight 1257 +/- 423 g) were assessed at 32 weeks GA in the NICU. OUTCOME MEASURES: The Newborn Developmental Care and Assessment Program (NIDCAP) and Neonatal Facial Coding System (NFCS) were coded from continuous bedside video recordings. Changes in mean heart rate (HR) were computed using custom physiologic software. RESULTS: All infants had heightened facial, body and HR responses when CC followed a painful procedure compared to when they had not been handled prior to CC. Infants born at earlier GA (<30 weeks) had equal numbers of stress cues during RCC and PCC, but dampened self-regulatory behaviors during PCC. CONCLUSION: Prior pain induces heightened biobehavioral reactivity in preterm infants during subsequent tactile procedures. In addition, clustering care is particularly stressful for infants born at earlier GA.     

Prenatal maternal cortisol levels and infant behavior during the first 5 months

BACKGROUND AND AIMS: Research on both animals and humans is providing more and more evidence that prenatal factors can have long-term effects on development. Most human studies have examined the effects of prenatal stress on birth outcome (i.e. shorter pregnancies, smaller infants). The few studies that have looked at the infants' later development have found prenatal stress to be related to more difficult temperament, behavioral/emotional problems and poorer motor/cognitive development. In this paper, we have examined links between late pregnancy cortisol levels and infant behavior during the first 5 months of life. STUDY DESIGN AND SUBJECTS: Seventeen mothers and their healthy, full-term infants participated in this prospective, longitudinal study. The mothers' cortisol was determined in late pregnancy. The infants' behavior was videotaped during a series of bath sessions at the home: at 1, 3, 5, 7, 18 and 20 weeks of age. The mothers filled in temperament questionnaires (ICQ) in postnatal weeks 7 and 18. RESULTS AND CONCLUSIONS: The infants were divided into two groups based on their mothers' late pregnancy cortisol values: high and low prenatal cortisol groups. A trend was found for the high cortisol infants to be delivered earlier than the low cortisol group. Furthermore, the behavioral observations showed the higher prenatal cortisol group to display more crying, fussing and negative facial expressions. Supporting these findings, maternal reports on temperament also showed these infants to have more difficult behavior: they had higher scores on emotion and activity. The differences between the infants were strongest at the youngest ages (weeks 1-7).     

Prenatal maternal stress programs infant stress regulation

Objective: Prenatal exposure to inappropriate levels of glucocorticoids (GCs) and maternal stress are putative mechanisms for the fetal programming of later health outcomes. The current investigation examined the influence of prenatal maternal cortisol and maternal psychosocial stress on infant physiological and behavioral responses to stress. Methods: The study sample comprised 116 women and their full term infants. Maternal plasma cortisol and report of stress, anxiety and depression were assessed at 15, 19, 25, 31 and 36 + weeks’ gestational age. Infant cortisol and behavioral responses to the painful stress of a heel‐stick blood draw were evaluated at 24 hours after birth. The association between prenatal maternal measures and infant cortisol and behavioral stress responses was examined using hierarchical linear growth curve modeling. Results: A larger infant cortisol response to the heel‐stick procedure was associated with exposure to elevated concentrations of maternal cortisol during the late second and third trimesters. Additionally, a slower rate of behavioral recovery from the painful stress of a heel‐stick blood draw was predicted by elevated levels of maternal cortisol early in pregnancy as well as prenatal maternal psychosocial stress throughout gestation. These associations could not be explained by mode of delivery, prenatal medical history, socioeconomic status or child race, sex or birth order. Conclusions: These data suggest that exposure to maternal cortisol and psychosocial stress exerts programming influences on the developing fetus with consequences for infant stress regulation.     

Maternal and paternal height and BMI and patterns of fetal growth: The Pune Maternal Nutrition Study

We examined the differential associations of each parent's height and BMI with fetal growth, and examined the pattern of the associations through gestation. Data are from 557 term pregnancies in the Pune Maternal Nutrition Study. Size and conditional growth outcomes from 17 to 29 weeks to birth were derived from ultrasound and birth measures of head circumference, abdominal circumference, femur length and placental volume (at 17 weeks only). Parental height was positively associated with fetal head circumference and femur length. The associations with paternal height were detectible earlier in gestation (17-29 weeks) compared to the associations with maternal height. Fetuses of mothers with a higher BMI had a smaller mean head circumference at 17 weeks, but caught up to have larger head circumference at birth. Maternal but not paternal BMI, and paternal but not maternal height, were positively associated with placental volume. The opposing associations of placenta and fetal head growth with maternal BMI at 17 weeks could indicate prioritisation of early placental development, possibly as a strategy to facilitate growth in late gestation. This study has highlighted how the pattern of parental-fetal associations varies over gestation. Further follow-up will determine whether and how these variations in fetal/placental development relate to health in later life.     

Longitudinal follow-up of height up to five years of age in infants born preterm small for gestational age; comparison to full-term small for gestational age infants

OBJECTIVE: This aims to conduct a comparative study of the height catch-up rate in preterm small for gestational age (SGA) infants during early childhood by gestational age and identify the factors affecting short stature in comparison to full-term SGA infants. METHODS: 449 SGA infants (214 full-term infants, 73 infants with gestation of less than 32 weeks, and 162 infants with gestation of more than 32 weeks but less than 37 weeks) from 25 institutions in Japan were assessed for catch-up (> or = -2SD) rate in growth by measuring for length/height at 1 year, 3 years and 5 years of age and the risk factors for no catch-up (< -2SD) at 5 years. RESULTS: The overall length/height catch-up rate was 68% at 1 year, 89% at 3 years and 88% at 5 years. The catch-up rate at 3 and 5 years of age in the group with gestation of less than 32 weeks had a rate of 74%, which was significantly less than the other two groups (approximately 90%). A significant factor associated with short stature at 5 years in the group with gestation of less than 32 weeks was the lower length SD score at time of birth, and for preterm infants born more than 32 weeks of gestation and full-term infants, significant factors were the lower maternal height and head circumference at birth. CONCLUSION: SGA infants born less than 32 weeks of gestation had a higher risk of no catch-up and different factors affecting catch-up compared to preterm SGA infants of gestation more than 32 weeks and full-term SGA infants.     

Depressive symptoms among rural Bangladeshi mothers: implications for infant development

OBJECTIVE: To examine how maternal depressive symptoms are related to infant development among low-income infants in rural Bangladesh and to examine how the relationship is affected by maternal perceptions of infant irritability and observations of caregiving practices. METHODS: Development was measured among 221 infants at 6 and 12 months with the Bayley Scales II. Mothers reported on their depressive symptoms and on perceptions of their infant's temperament, and a home visit was made to complete the HOME Inventory. RESULTS: Half (52%) the mothers reported depressive symptoms. In bivariate analyses, maternal depressive symptoms were related to low scores on the Bayley Scales. Infants whose mothers reported depressive symptoms and perceived their infants to be irritable acquired fewer cognitive, motor, and Orientation/Engagement skills between 6-12 months than infants whose mothers reported neither or only one condition. The relationship linking maternal depressive symptoms and perceived infant irritability with infant cognitive skills was partially mediated by parental responsiveness and opportunities for play in the home. CONCLUSIONS: The intergenerational risks of maternal depressive symptoms on infant development extend to rural Bangladesh and are accentuated when mothers perceive their infants as irritable. Mothers who report depressive symptoms and infant irritability may lack the capacity to provide responsive, developmentally-oriented caregiving environments.     

The effect of zinc supplementation during pregnancy on immune response to Hib and BCG vaccines in Bangladesh

An essential role for zinc in development of the fetal immune system has been documented. However, the effect of antenatal zinc supplementation on infants' postnatal immune response to vaccinations is unknown. The objective of this study was to evaluate the effect of zinc supplementation during pregnancy on immune response to the Bacillus Calmette-Guerin (BCG) vaccine and the Haemophilus influenzae type b (Hib) component of the combined diphtheria, tetanus toxoid and pertussis (DTP)-Haemophilus influenzae type-b (Hib)- conjugate vaccine in poor Bangladeshi infants. We immunized 405 infants whose mothers were supplemented daily with 30 mg elemental zinc or placebo beginning at 12-16 weeks gestation with the standard BCG vaccine at birth. A subcohort of 203 infants were in addition immunized at 1-month intervals with three doses of DTP-Hib vaccine starting at 9 weeks of age. The delayed hypersensitivity (PPD) skin test was performed in 345 infants at 24 weeks of age. Hib polysaccharide (PRP) antibodies were assessed for 91 infants at 4 and 24 weeks of age. In infants born with low birth weight (LBW) a lower proportion of negative responses to PPD skin test were observed in the zinc (66.2%) compared to placebo (78.5%) group (p = 0.07). No differences were observed in normal birth weight infants. There were no differences in proportion of infants above the protective thresholds for anti-PRP antibodies between zinc (81%) and placebo (89%) group. Geometric mean PRP antibody titres at 4 and 24 weeks of age were not different between groups. Zinc supplementation during pregnancy did not enhance immune response to Hib-conjugate vaccine but there was a suggestion of improved delayed hypersensitivity immune responses to BCG-vaccine in Bangladeshi LBW infants.     

Serial evaluation for myocardial performance in fetuses and neonates using a new Doppler index

BACKGROUND: Fetal echocardiography has been used for non-invasive evaluation of human fetal cardiac anatomy, function and hemodynamics. The Tei index, a new Doppler index known to be independent of both ventricular geometry and heart rate, has recently been applied to the evaluation of myocardial performance. METHODS: In the present study, the Tei index was prospectively and longitudinally determined in 50 normal fetuses, 35 fetuses with intrauterine growth retardation (IUGR), 30 fetuses of diabetic mothers (DM) and 20 normal infants. The Tei index of both left and right ventricles was calculated from a Doppler ventricular inflow and outflow trace using the following formula: Tei index = (ICT + IRT)/ET, where ICT is isovolumetric contraction time; IRT, isovolumetric relaxation time; and ET, ejection time). RESULTS: The Tei index of the left ventricle decreased linearly with advancing gestational age during 18-33 weeks and decreased acceleratively with increasing gestational age after 34 weeks. The index of the right ventricle decreased slightly and linearly with advancing gestational age during 18-41 weeks. In neonates, the Tci index of the left and right ventricle increased immediately and transitorily after birth and decreased and stabilized after 24 h of life. From 18 to 26 weeks of gestation, the Tei indices in fetuses with IUGR and of DM were not significantly different from controls. However, from 27 to 40 weeks of gestation, the Tei indices in both fetuses with IUGR and of DM were significantly greater than controls. CONCLUSIONS: This gradual decrease in the Tei index during gestation may represent the maturational or developmental alternation of myocardial performance in utero. Fetuses with IUGR and of DM may have abnormal myocardial performance in later gestation.     

Fetal mediators of the relationships between increased pregnancy and labour blood pressure and newborn irritability

A prospective study of primiparous English women and their newborns failed to replicate previous findings that greater irritability was related to higher maternal blood pressure during pregnancy and labour. This apparent lack of replication prompted a search for fetal variables capable of mediating the blood pressure--irritability relationships. Relative fetal growth retardation was found in newborns of women whose peak antenatal blood pressure occurred from 20 to 32 wk gestation. Prenatal growth retardation and exposure to either oxytocin-stimulated labour or higher maternal blood pressure during spontaneous labour were associated with lower intrapartum fetal heart rate. Lower heart rate, in turn, was associated with greater crying and more frequent changes of state during behavioural assessments on the first and fifth days. It is suggested that intrapartum hypoxia is an immediate antecedent of newborn irritability. The blood pressure--irritability relationships may therefore reflect the influence of growth retardation, attributable to increased pregnancy blood pressure, and higher labour blood pressure, respectively, on the ability of the fetus to withstand hypoxia and the degree of hypoxia encountered during labour.     

Survival and neonatal morbidity at the limits of viability in the mid 1990s: 22 to 25 weeks

OBJECTIVE: We determined neonatal survival and morbidity rates based on both fetal (stillborn) and neonatal deaths for infants delivered at 22 to 25 weeks' gestation. STUDY DESIGN: Two hundred seventy-eight deliveries at 22 to 25 weeks' completed gestation were analyzed by gestational age groups between January 1993 and December 1997. Logistic regression models were used to identify maternal and neonatal factors associated with survival. RESULTS: The rate of fetal death was 24%; 76% of infants were born alive and 46% survived to discharge. Survival rates including fetal death at 22, 23, 24, and 25 weeks were 1.8%, 34%, 49%, and 76%; and survival rates excluding fetal death were 4.6%, 46%, 59%, and 82%, respectively. Logistic regression analyses showed that higher gestational age (P<.0002), higher birth weight (P<.001), female sex (P<.005), and surfactant (P<.003) were associated with neonatal survival. Cesarean section was associated with decreased survival (P <.006). CONCLUSION: Hospital neonatal survival rates of infants at the limits of viability are significantly lower with the inclusion of fetal deaths. This information should be considered when providing prognostic advice to families when mothers are in labor at 22 to 25 weeks' gestation.     

Temperament in infants born prematurely

The temperament of infants born prematurely was studied to examine further the notion that prematurity may be a risk factor for an infant's subsequent social interaction. The Infant Temperament Questionnaire of Carey and McDevitt was revised and revalidated for an Australian population and sent to mothers of infants who had been born prematurely (36 weeks or less) and who were aged 4 to 8 months (corrected for prematurity). Two hundred and twenty-six questionnaires were distributed and 110 (49%) returned. There were no differences between respondents and nonrespondents with respect to gestational age, birth weight, method of delivery, Apgar scores, or perinatal complications. When compared to a control group (N = 240) of infants born at term and who came from families with similar demographic characteristics, infants born prematurely did not differ significantly on any of the nine temperament dimensions. Both groups had similar proportions of "easy," "difficult," and "slow to warm up" infants, and there were no significant differences in maternal global ratings of temperament between the two groups. Comparisons of infants of less than 33 weeks gestation gave results similar to those reported above. These data indicate that infants born prematurely have temperament profiles at 4 to 8 months similar to infants born at term.     

Survival of very preterm infants: Epipage, a population based cohort study

OBJECTIVE: To evaluate the outcome for all infants born before 33 weeks gestation until discharge from hospital. DESIGN: A prospective observational population based study. SETTING: Nine regions of France in 1997. PATIENTS: All births or late terminations of pregnancy for fetal or maternal reasons between 22 and 32 weeks gestation. MAIN OUTCOME MEASURE: Life status: stillbirth, live birth, death in delivery room, death in intensive care, decision to limit intensive care, survival to discharge. RESULTS: A total of 722 late terminations, 772 stillbirths, and 2901 live births were recorded. The incidence of very preterm births was 1.3 per 100 live births and stillbirths. The survival rate for births between 22 and 32 weeks was 67% of all births (including stillbirths), 85% of live births, and 89% of infants admitted to neonatal intensive care units. Survival increased with gestational age: 31% of all infants born alive at 24 weeks survived to discharge, 78% at 28 weeks, and 97% at 32 weeks. Survival among live births was lower for small for gestational age infants, multiple births, and boys. Overall, 50% of deaths after birth followed decisions to withhold or withdraw intensive care: 66% of deaths in the delivery room, decreasing with increasing gestational age; 44% of deaths in the neonatal intensive care unit, with little variation with gestational age. CONCLUSION: Among very preterm babies, chances of survival varies greatly according to the length of gestation. At all gestational ages, a large proportion of deaths are associated with a decision to limit intensive care.     

Risk factors for unexplained antepartum fetal death in Norway 1967-1998

OBJECTIVE: To relate unexplained antepartum fetal death with maternal and fetal characteristics in order to identify risk factors. DESIGN: Population-based study based on records of 1,676,160 singleton births with gestational age > or =28 weeks. Unexplained antepartum fetal death was defined as fetal death before labour without known fetal, placental, or maternal pathology. RESULTS: Although unexplained fetal mortality in general declined from 2.4 per 1000 births in 1967-1976 to 1.6 in 1977-1998, the proportion among all fetal deaths increased from 30% to 43% during the same period of observation. Unexplained fetal death occurred later in gestation than explained. From 39 weeks of gestation, the risk increased progressively to 50/10,000 in women aged > or =35 years and <10/10,000 in women <25 years. In birth order > or =5, the risk was particularly high after 39 weeks of gestation. For birth weight percentile 2.5-9.9 and > or =97.5, unexplained fetal death was four and three times more likely to occur, respectively. We found an additive effect of maternal age and birth weight percentile 2.5-9.9. Women with less than 10 years education had higher risk than women with 13 years or more (OR=1.6). Weaker associations were observed with female gender, unmarried mothers, and winter season. CONCLUSIONS: Unexplained antepartum fetal death occurred later in gestation than explained and was associated with high maternal age, multiparity, low education, and moderately low and high birth weight percentile. The increased risk in post-term pregnancies and the additive effect of maternal age and birth weight percentile 2.5-9.9 suggests that older women would benefit from monitoring of fetal growth.     

Plasma cortisol, cortisone and urinary glucocorticoid metabolites in preterm infants

OBJECTIVE AND METHODS: In the fetal circulation, there is a low cortisol:cortisone (F:E) ratio ( approximately 0.3) suggesting high activity of 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2). The circulating F:E ratio rises after birth in term infants, but little is known about infants born prematurely. Our hypothesis was that the low fetal plasma F:E ratio would persist in infants born prematurely, due to persistently high tissue 11betaHSD2 activity. To test this hypothesis, a longitudinal observational study of plasma F, E levels and urinary F and E metabolites was performed in 22 preterm infants of 24-31 weeks gestation. RESULTS: Median plasma F was 234-380 nmol l(-1), median 124-177 nmol l(-1) from 1 to 14 days age. Plasma F fell with increasing postnatal and postconceptional age. The F:E ratio was 3 in the first week of life, and thereafter was 1-2, falling with postnatal age. Urinary glucocorticoid metabolites were low in quantity ( approximately 48-120 microg kg(-1) day(-1)), consisted of E metabolites until term, and did not reflect the plasma F:E ratio. CONCLUSIONS: The fetal plasma F:E ratio did not persist in these preterm infants, due to tenfold higher levels of F. The F:E ratios were similar to those reported in term infants. These data suggest that the low F:E ratio in utero is due to low fetal production of cortisol, and effective placental inactivation of maternal F by 11betaHSD2.     

Outcome after antenatal diagnosis of upper urinary tract dilatation by ultrasonography.

A prospective study was carried out during 1986 to find out the incidence of fetal renal tract anomalies in 3228 pregnant mothers delivered in one hospital. Ultrasound examination of the fetus was performed as part of the routine antenatal assessment at 16-20 weeks'' gestation, and later examinations were done if there were obstetric indications. Fetuses with any degree of dilatation of the renal pelvis or other renal tract anomalies were followed up with serial ultrasound examinations in utero and then postnatally at 6 days and 6 weeks of age, or earlier if indicated. No renal tract anomalies were detected before 28 weeks'' gestation, but of 761 fetuses examined later, 62 had dilatation of the renal pelvis not associated with overdistended bladders, and one fetus was anephric. After birth 10 of these infants (16%) were found to have pronounced renal tract abnormalities. Three who had associated serious congenital abnormalities died, five infants had obstruction of the pelviureteric junction, and two infants had vesicoureteric reflux. Antenatal ultrasonographic examination after 28 weeks identifed pronounced renal tract abnormalities in asymptomatic infants with a frequency of 9.2/1000 births (seven of 761) thus permitting early treatment and reducing the incidence of late complications.     

The postnatal changes in red blood cell NO levels

AIM: To determine the levels of RBC HbSNO and HbFe(II)NO using chemiluminescence in very low birth weight infants breathing room air, during the first 2 days of life. METHOD: RBC NO values were compared to the levels obtained in cord blood at birth from infants of similar gestational age. Five infants ranging from 25 to 27 weeks of gestation were sampled between 12 and 24 h after birth. These infants were considered as the postnatal group and had normal blood gases at room air. RESULTS: The HbSNO levels were increased in the postnatal group from 49.0 +/- 17.4 nm to 152.3 +/- 54.3 nm (p = 0.0006). There was no difference in HbFe(II)NO levels between the two groups (mean of 267.6 +/- 186.5 nm in cord blood and 180.3 +/- 89.2 nm in the postnatal sample. CONCLUSION: The increase in HbSNO postnatally could be an important mechanism for the neonatal pulmonary adaptation to extra-uterine life.     

Observational study of maternal anthropometry and fetal insulin.

AIMS: To examine the relation between maternal body fat and fetal metabolism. METHODS: In this observational study, cord blood samples were collected from 60 infants of healthy women for the measurement of insulin and C peptide concentrations. Maternal weight, height, body mass index (BMI) and body composition (skinfold thickness measurements and bioelectrical impedance) were assessed at 13-15 weeks of gestation. Twenty five of the volunteers agreed to have a 75 g oral glucose tolerance test at 28-31 weeks of gestation. RESULTS: Positive correlations were observed with both cord insulin or C peptide concentrations and maternal early pregnancy BMI (r=0.44, p=0.002 and r=0.33, p=0.008, respectively). There was no significant correlation between cord insulin or C peptide concentrations and birthweight or birth weight centiles. CONCLUSION: Maternal BMI could be a predictor of fetal cord insulin concentration.     

Developmental patterns of heart rate and variability in prematurely-born infants with apnea of prematurity

At equivalent post-conceptional ages, prematurely-born infants have higher heart rates and reduced heart rate variability, relative to full-term neonates. Premature birth might exert long-lasting effects on central and peripheral mechanisms that control cardiovascular activity. We assessed development of heart rate and heart rate variability in symptomatic preterm infants up to 6 months of age. Fifty 6.5-h evening recordings of EKG and breathing were obtained from prematurely-born infants (gestational ages: 24–35 weeks). Cardiac R-R intervals were captured with a resolution of ±0.5 msec. One-min epochs were selected from three periods of regular respiration in recordings from premature infants and 72 recordings of full-term infants at comparable post-conceptional ages. Mean heart rate and heart rate variability were determined for each recording. At 40 weeks post-conception, prematurely-born infants with apnea of prematurity showed higher heart rates and reduced heart rate variability than did full-term neonates. These differences between premature and full-term infants persisted throughout the next 6 months in those infants born prior to 30 weeks gestation, and in those infants born at 30–35 weeks who experienced respiratory distress syndrome (RDS) during the neonatal period. The findings suggest that premature delivery, or complications thereof, exerts long-lasting effects on cardiac control.