Abstract
BACKGROUND:
Newborn assessment using Umbilical arterial blood gas (UABG) analysis is more objective than other methods for predicting neonatal outcome. Acidic neonates may be at risk of adverse consequences after birth. This study was conducted to determine the risk factors during pregnancy and their effect on the arterial blood gas (ABG) of the neonates after birth.
MATERIALS AND METHODS:
This cross-sectional study was conducted on 1794 mothers hospitalized for termination of pregnancy who were referred to Imam Hossein Medical Training Center in Tehran during the years 2021–2023. Information was collected through a checklist before and after delivery. Also, to perform ABG and VBG, a blood sample was taken from the neonate’s umbilical cord and extracted from the file. Data analysis was done using SPSS version 25 statistical software.
RESULTS:
In this study, between different ABG levels and maternal characteristics, BMI, oligohydramnios, placental abruption, IUGR, acreta, PPROM, delivery mode, and labor with induction, COVID-19, HTN, heart disease, anemia, diabetes, gestational diabetes, pre-eclampsia, eclampsia and addiction statistically significant difference was observed (P < 0.05). A significant difference was observed between preterm infants, weighing less than 2500 grams, Apgar score lower than 7 in the first and fifth minutes, and hospitalization in NICU with different levels of ABG PH (P < 0.05). In the multivariable model, fetal distress (OR: 3.51, 95% CI: 1.91–6.44), GDM (Insulin, OR = 5.08; 95% CI: 2.60–9.95), Gestational age at birth (<37, OR = 2.25; 95% CI: 1.23–4.12) were associated with an increased odds of ABG acid level. Also, in the multivariable model, fetal distress (OR: 2.30, 95% CI: 1.70–3.12), GDM (Insulin, OR = 2.48; 95% CI: 1.70–3.64 and diet, OR = 2.42; 95% CI: 1.46–4.02), Labor (Induction, OR = 1.61; 95% CI: 1.10–2), Gestational age at birth (<37, OR = 1.43; 95% CI: 1.06–1.92) were associated with an increased odds of ABG hypoxia level.
CONCLUSION:
It can be concluded that umbilical cord blood gas is closely related to neonatal prognosis and is a useful tool for screening newborns at risk. ABG should be considered for all deliveries, as it is an accurate screening test for hypoxia and neonatal asphyxia.
Keywords: Asphyxia, hypoxia, neonatal, PH, umbilical arterial blood gas
Introduction
Clinical evidence shows that despite significant advances in midwifery and labor management in recent years, the incidence of hypoxia and asphyxia during labor remains high, and about 10% of newborns require some degree of active resuscitation to activate breathing, and 1% require extensive care.[1,2]
In recent years, the value of clinical application of umbilical arterial blood gas (UABG) analysis of newborns has gradually attracted the attention of the perinatal medical community.[3] Arterial blood gas (ABG) analysis mainly analyzes indicators such as power of hydrogen (PH), partial pressure of carbon dioxide (PCO2), partial pressure of oxygen (PO2), bicarbonate radical (HCO3−), alkali surplus and anion gap, which is an objective and valid tool to assess the oxygenation and metabolic status of the newborn at birth.[4,5,6] The oxygen needed by the fetus is supplied from the umbilical cord and the maternal placenta. When oxygen cannot meet the needs of the fetus, anaerobic metabolism increases, leading to excessive production of CO2 and lactic acid metabolites. The blood buffer system in the fetus is mainly carbonic acid. The hydrogen salt buffer system and the hemoglobin buffer system cannot completely remove excess acidic substances, which prevents them from regulating the acid-base balance in the body, leading to acidosis.[3]
Fetal and neonatal acidemia is associated with several adverse neonatal outcomes. These outcomes include low Apgar score, respiratory distress syndrome (RDS), cerebral involvement in the form of cerebral palsy and developmental delay, hypoxic ischemic encephalopathy (HIE), seizures, intraventricular hemorrhage, sepsis, and death.[7,8,9,10,11,12] A systematic review and meta-analysis of 481,753 infants reported that low cord arterial pH was significantly associated with neonatal mortality, HIE, intraventricular hemorrhage, and cerebral palsy.[13] Determining the timing of injury is essential to understanding the mechanisms underlying these outcomes.
There are also several factors that may affect the acid-base balance in cord blood. These factors can be divided into maternal and fetal factors and factors that are directly related to the uterine wall, placenta, or umbilical cord. Maternal diseases such as causes such as maternal bleeding, maternal hypotension, uterine hypertension, decollement, umbilical cord pressure, severe maternal cardiopulmonary diseases, preeclampsia, diabetes, anemia, and heart disorders, can be mentioned.[14,15]
Considering that the burden of infant mortality and morbidity is very high in developing countries.[16] Therefore, evidence-based strategies are needed for the early prediction and management of adverse neonatal outcomes. According to previous studies, ABG (umbilical cord blood) analysis can be effective for detecting infant asphyxia.[17,18] In this regard, this study was conducted to investigate the relationship between pregnancy risk factors and ABG and VBG umbilical cord of the infant after birth.
Materials and Methods
Study design and setting
This cross-sectional study was conducted on participants at Imam Hossein Hospital in Tehran, Iran, between 2021 and 2023.
Study participants and sampling
This cross-sectional study included all pregnant women admitted for termination of pregnancy at Imam Hossein Hospital, Tehran, Iran, during the study period.
Participants were selected by census sampling based on the inclusion and exclusion criteria.
Inclusion criteria, all pregnant women who went to the hospital and ended their pregnancy, and sent ABG and VBG samples after birth. The exclusion criteria included lack of access to sufficient information. At the end of the study period, a total of 1797 mothers were enrolled in the study.
Data collection tool and technique
Patient information (no patient name) was collected through the checklist and the analysis of newborn ABG/VBG blood gases, by sending the umbilical cord samples of newborns immediately after birth to the center’s laboratory and providing a report by the laboratory.
The checklist made by the researcher for data collection includes the mother’s demographic information (mother’s age and BMI), mother’s clinical information (heart disease, diabetes, kidney disease, pre-eclampsia, anemia, hepatitis, HIV, thyroid problems and covid-19), problems during pregnancy and delivery of the mother (oligohydramnios and polyhydramnios, rupture of the amniotic sac, premature rupture of the amniotic sac, meconium, intrauterine growth disorder, placental abruption, decollement, accreta, bleeding during pregnancy, type of delivery, prolonged labor, Induction of labor, elective cesarean section, emergency cesarean sections due to lack of progress in labor, meconium and fetal distress), newborn information (term, preterm, and premature, gender, Apgar score, weight, outcome (hospitalization in NICU) and blood gas analysis was ABG/VBG of the newborn, which was completed by a trained nurse.
Data analysis
Numbers and percentages were used to report categorical variables, and mean ± SD was used for continuous variables. Chi-square test and one-way ANOVA were used to compare basic features. univariable and multivariable logistic regression analyses were performed to identify factors associated with ABG acidemia and hypoxia levels. Backward stepwise elimination was used to remove non-significant variables until only statistically significant variables remained in the final logistic model. Crude and adjusted odds ratios and their corresponding 95% Confidence Intervals (CI) were computed in the univariable and multivariable logistic regression analysis, respectively. Data were analyzed using SPSS software version 25; all statistical significance was declared at P < 0.05.
Ethical consideration
Ethical considerations were taken into account in this study. The study was approved by the Ethics Committee of Shahid Beheshti University of Medical Sciences with the code (IR.SBMU.MSP.REC.1401.659).
Results
During three years, 1797 mothers admitted to Imam Hossein Hospital for termination of pregnancy were included in the study. The information is given in Table 1.
Table 1.
Relationship between maternal and infant characteristics with different levels of ABG
| Variables | Level ABG |
P | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| <7 n (%) | 7–7.2 n (%) | >7.2 n (%) | Total n (%) | |||||||
| Age (year) | ||||||||||
| <18 18–35 >35 |
3 (2.7) 32 (3.2) 16 (2.4) |
23 (20.5) 173 (17.1) 128 (19.0) |
86 (76.8) 808 (79.8) 528 (78.6) |
112 (100) 1013 (100) 672 (100) |
0.67 | |||||
| Maternal BMI | ||||||||||
| Normal Overweight Obese |
9 (7.1) 3 (1.3) 38 (2.7) |
22 (17.3) 49 (21.2) 252 (17.6) |
96 (75.6) 179 (77.5) 1140 (79.9) |
127 (100) 231 (100) 1430 (100) |
0.02 | |||||
| Oligohydramnios | ||||||||||
| + − |
8 (9.4) 43 (2.5) |
63 (74.1) 261 (15.2) |
14 (16.5) 1408 (82.2) |
85 (100) 1712 (100) |
<0.001 | |||||
| Polyhydramnios | ||||||||||
| + − |
2 (2.4) 49 (2.9) |
17 (20.2) 307 (17.9) |
65 (77.4) 1357 (79.2) |
84 (100) 1713 (100) |
0.84 | |||||
| Placental abruption | ||||||||||
| + − |
3 (9.7) 48 (2.7) |
12 (38.7) 312 (17.7) |
16 (51.6) 1406 (79.6) |
31 (100) 1766 (100) |
<0.001 | |||||
| IUGR | ||||||||||
| + − |
13 (5.1) 38 (2.5) |
82 (32.2) 242 (15.7) |
160 (62.7) 1262 (81.8) |
255 (100) 1542 (100) |
<0.001 | |||||
| Acreta | ||||||||||
| + − |
0 51 (2.9) |
7 (46.7) 317 (17.8) |
8 (53.3) 1414 (79.3) |
15 (100) 1782 (100) |
0.01 | |||||
| PPROM | ||||||||||
| + − |
10 (6.9) 41 (2.5) |
32 (22.1) 292 (17.7) |
103 (71.0) 1319 (79.8) |
145 (100) 1652 (100) |
0.003 | |||||
| PROM | ||||||||||
| + − |
2 (3.8) 49 (2.8) |
11 (20.8) 313 (17.9) |
40 (75.5) 1382 (79.2) |
53 (100) 1744 (100) |
0.78 | |||||
| Episiotomy | ||||||||||
| + − |
32 (6) 66 (5.2) |
85 (15.8) 219 (17.4) |
420 (78.2) 973 (77.3) |
537 (100) 1258 (100) |
0.62 | |||||
| Delivery mode | ||||||||||
| NVD elective/rep C/S C/S due to labor arrest C/S due to meconium C/S due to fetal distress |
29 (3.7) 5 (0.9) 0 (0) 0 (0) 17 (6.0) |
115 (14.8) 90 (15.5) 9 (11.7) 15 (18.8) 95 (33.5) |
632 (81.4) 485 (83.6) 68 (88.3) 65 (81.3) 172 (60.6) |
776 (100) 580 (100) 77 (100) 80 (100) 284 (100) |
<0.001 | |||||
| Labor | ||||||||||
| Spontaneously Induction Misoprostal |
38 (3.2) 8 (4.0) 2 (2.4) |
200 (16.8) 48 (24.2) 24 (28.6) |
953 (80.0) 142 (71.7) 58 (69.0) |
1191 (100) 198 (100) 84 (100) |
0.01 | |||||
| chorioamnionitis | ||||||||||
| + − |
1 (12.5) 50 (2.8) |
2 (25.0) 322 (18.0) |
5 (62.5) 1417 (79.2) |
8 (100) 1789 (100) |
0.20 | |||||
| Shoulder dystocia | ||||||||||
| + − |
0 (0) 51 (2.9) |
2 (14.3) 322 (18.1) |
12 (85.7) 1410 (79.1) |
14 (100) 1783 (100) |
0.74 | |||||
| HX of Abortion | ||||||||||
| + − |
13 (3.3) 38 (2.7) |
85 (21.4) 239 (17.1) |
300 (75.4) 1122 (80.2) |
398 (100) 1399 (100) |
0.11 | |||||
| Gravid | ||||||||||
| Nulipara Multipara |
17 (3.3) 34 (2.6) |
103 (20.2) 221 (17.2) |
390 (76.5) 1032 (80.2) |
510 (100) 1287 (100) |
0.21 | |||||
| COVID-19 | ||||||||||
| + − |
27 (16.6) 24 (1.5) |
88 (54.0) 236 (14.4) |
48 (29.4) 1374 (84.1) |
163 (100) 1634 (100) |
<0.001 | |||||
| HTN | ||||||||||
| + − |
8 (9.0) 43 (2.5) |
30 (33.7) 294 (17.2) |
51 (57.3) 1371 (80.3) |
89 (100) 1708 (100) |
<0.001 | |||||
| Heart disease | ||||||||||
| + − |
0 (0) 51 (2.9) |
8 (20.0) 316 (18.0) |
32 (80.0) 1390 (79.1) |
40 (100) 1757 (100) |
0.53 | |||||
| Anemia | ||||||||||
| + − |
1 (2.3) 50 (2.9) |
16 (36.4) 308 (17.6) |
27 (61.4) 1395 (79.6) |
44 (100) 1753 (100) |
0.006 | |||||
| Thyroid disease | ||||||||||
| + − |
3 (1.4) 48 (3.0) |
42 (19.2) 282 (17.9) |
174 (79.5) 1248 (79.1) |
219 (100) 1578 (100) |
0.35 | |||||
| Pregestational DM | ||||||||||
| +Insulin +diet − |
0 (0) 4 (12.1) 47 (2.7) |
7 (53.8) 28 (24.2) 309 (17.6) |
6 (46.2) 21 (63.6) 1395 (79.7) |
13 (100) 33 (100) 1751 (100) |
<0.001 | |||||
| GDM | ||||||||||
| +Insulin +diet − |
15 (7.2) 2 (1.7) 34 (2.3) |
58 (27.9) 37 (31.6) 229 (15.6) |
135 (64.9) 78 (66.7) 1209 (82.1) |
208 (100) 117 (100) 1472 (100) |
<0.001 | |||||
| Preeclampsia | ||||||||||
| + − |
31 (12.0) 20 (1.3) |
101 (39.0) 223 (14.5) |
127 (49.0) 1295 (84.2) |
259 (100) 1538 (100) |
<0.001 | |||||
| Eclampsia | ||||||||||
| + − |
25 (17.9) 73 (4.4) |
34 (24.3) 270 (16.3) |
81 (57.9) 1314 (79.3) |
140 (100) 1657 (100) |
<0.001 | |||||
| Hepatitis | ||||||||||
| + − |
1 (5.9) 50 (2.8) |
6 (35.2) 318 (17.9) |
10 (58.9) 1412 (79.3) |
17 (100) 1780 (100) |
0.08 | |||||
| Addict | ||||||||||
| + − |
17 (15.6) 34 (2.0) |
56 (51.4) 268 (15.9) |
36 (33.0) 1386 (82.1) |
109 (100) 1688 (100) |
<0.001 | |||||
| Neurologic Disease | ||||||||||
| + − |
3 (4.3) 95 (5.5) |
18 (25.7) 286 (16.6) |
49 (70) 1346 (77.9) |
70 (100) 1727 (100) |
0.13 | |||||
| Gestational age at birth | ||||||||||
| <37 37–41 >41 |
26 (4.8) 24 (2.0) 1 (1.3) |
128 (23.7) 179 (15.2) 17 (21.3) |
386 (71.5) 974 (82.8) 62 (77.5) |
540 (100) 1177 (100) 80 (100) |
<0.001 | |||||
| Sex | ||||||||||
| Girl Boy |
28 (3.3) 23 (2.5) |
141 (16.4) 183 (19.5) |
690 (80.3) 732 (78.0) |
859 (100) 938 (100) |
0.15 | |||||
| 1-minute apgar score | ||||||||||
| <7 >7 |
28 (9.9) 23 (1.5) |
78 (27.6) 246 (16.2) |
177 (62.5) 1245 (82.2) |
283 (100) 1514 (100) |
<0.001 | |||||
| 5-minute apgar score | ||||||||||
| <7 >7 |
22 (18.5) 29 (1.7) |
42 (35.3) 282 (16.8) |
55 (46.2) 1367 (81.5) |
119 (100) 1678 (100) |
<0.001 | |||||
| Birth weight (gr) | ||||||||||
| <2500 2500–4000 >4000 |
25 (8.3) 26 (1.8) 0 (0) |
92 (30.5) 222 (15.6) 10 (14.7) |
185 (61.3) 1179 (82.6) 58 (85.3) |
302 (100) 1427 (100) 68 (100) |
<0.001 | |||||
| Admission to NICU | ||||||||||
| + − |
21 (6.5) 30 (2.0) |
92 (28.6) 232 (15.7) |
209 (64.9) 1213 (82.2) |
322 (100) 1475 (100) |
<0.001 | |||||
According to the obtained results, there was no statistically significant relationship between mother’s age and different levels of ABG, but a significant difference was observed in terms of BMI (P < 0.05).
Pregnancy problems with different levels of ABG show, most babies with oligohydramnios had ABG PH (7–7.2). In terms of delivery, the highest percentage of hypoxia and acidemia is related to cesarean section due to fetal distress, and natural delivery with induction and misoprostol. A statistically significant difference was observed between different levels of ABG PH with oligohydramnios, placental abruption, IUGR, acreta, PPROM, delivery mode, and labor with induction (P < 0.05).
The relationship between the mother’s clinical condition and different levels of ABG shows that a high percentage of babies born to mothers with COVID-19 had hypoxia and acidemia. According to the findings, statistically significant differences were observed between HTN, heart disease, anemia, diabetes, gestational diabetes, pre-eclampsia, eclampsia, and addiction and different levels of ABG PH (P < 0.05).
The relationship between the neonates’ characteristics and different levels of ABG shows that the number of boy infants born with ABG PH (7–7.2) was more than that of girl infants, but it was not statistically significant. A significant difference was observed between preterm infants, weighing less than 2500 grams, Apgar score < 7 in the first and fifth minutes, and hospitalization in NICU with different levels of ABG PH (P < 0.05).
In a univariable model, a significant association was found between ABG acid level and fetal distress, PPROM, GDM, and gestational age at birth (P < 0.05). Multivariate logistic regression analysis shows that the odds of acidic ABG level in mothers with fetal distress are 3.51 times that of mothers without fetal distress. The odds of an acidic ABG level in mothers with gestational weeks less than 37 weeks are 2.25 times that of mothers with 37–41 weeks of gestation. The odds of an acidic ABG level in mothers with gestational diabetes treated with insulin were 5.08 times that of healthy mothers [Table 2]. The results of the logistic regression model were examined in terms of model fit using the Hosmer–Lemeshow test and the ROC curve, so that the results of the Hosmer–Lemeshow test were not significant and the ROC curve showed a level below the curve of 0.74; therefore, the model is statistically accepted.
Table 2.
Relationship between maternal and infant characteristics with ABG acid level
| ABG PH (<7) | Crude | Adjusted | ||||||
|---|---|---|---|---|---|---|---|---|
|
|
|
|||||||
| OR (95% CI) | P | OR (95% CI) | P | |||||
| Fetal Distress | ||||||||
| − | 1 | – | 1 | – | ||||
| + | 4.66 (2.63–8.24) | <0.001 | 3.51 (1.91–6.44) | <0.001 | ||||
| Labor arrest | ||||||||
| − | 1 | – | 1 | – | ||||
| + | 0.47 (0.14–1.55) | 0.22 | – | – | ||||
| PPROM | ||||||||
| − | 1 | – | 1 | – | ||||
| + | 3.12 (1.52–6.41) | 0.002 | – | |||||
| GDM | ||||||||
| − | 1 | – | 1 | – | ||||
| +diet | 0.91 (0.21–3.86) | 0.90 | 1.01 (0.23–4.45) | 0.98 | ||||
| +Insulin | 3.95 (2.09–7.44) | <0.001 | 5.08 (2.60–9.95) | <0.001 | ||||
| Labor | ||||||||
| Spontaneously | 1 | – | 1 | – | ||||
| Induction | 1.41 (0.64–3.09) | 0.38 | – | – | ||||
| Misoprostal | 0.84 (0.86–0.20) | 0.84 | – | – | ||||
| Gestational age at birth | ||||||||
| 37–41 | 1 | – | 1 | – | ||||
| <37 | 2.73 (1.55–4.82) | <0.001 | 2.25 (1.23–4.12) | 0.009 | ||||
| >41 | 0.65 (0.08–4.91) | 0.68 | 0.43 (0.06–3.72) | 0.48 | ||||
In a univariable model, a significant association was found between ABG hypoxia level and fetal distress, HX of Abortion, GDM, Labor, and gestational age at birth (P < 0.05). In the multivariable model, fetal distress (OR: 2.30, 95% CI: 1.70–3.12), GDM (Insulin, OR = 2.48; 95% CI: 1.70–3.64 and diet, OR = 2.42; 95% CI: 1.46–4.02), Labor (Induction, OR = 1.61; 95% CI: 1.10–2), Gestational age at birth (<37, OR = 1.43; 95% CI: 1.06 – 1.92) were associated with an increased odds of ABG hypoxia level [Table 3]. The fit of the model was evaluated using the Hosmer–Lemeshow test and the ROC curve. The Hosmer–Lemeshow test was not significant, and the ROC curve showed a level below the curve of 0.66, so the model is statistically accepted.
Table 3.
Relationship between maternal and infant characteristics with ABG hypoxia level
| Hypoxia | Crude | Adjusted | ||||||
|---|---|---|---|---|---|---|---|---|
|
|
|
|||||||
| OR (95% CI) | P | OR (95% CI) | P | |||||
| Fetal Distress | ||||||||
| − | 1 | – | 1 | – | ||||
| + | 2.79 (2.12–3.67) | <0.001 | 2.30 (1.70–3.12) | <0.001 | ||||
| HX of Abortion | ||||||||
| − | 1 | – | 1 | – | ||||
| + | 1.33 (1.00– 1.75) | 0.04 | – | – | ||||
| GDM | ||||||||
| − | 1 | – | 1 | – | ||||
| +diet | 2.50 (1.65–3.79) | <0.001 | 2.42 (1.46–4.02) | 0.001 | ||||
| + Insulin | 2.26 (1.61–3.18) | <0.001 | 2.48 (1.70–3.64) | <0.001 | ||||
| Labor | ||||||||
| Spontaneously | 1 | – | 1 | – | ||||
| Induction | 1.61 (1.12–2.31) | 0.01 | 1.61 (1.10–2.35) | 0.01 | ||||
| Misoprostal | 1.97 (1.19–3.24) | 0.008 | 1.61 (0.95–2.72) | 0.07 | ||||
| Gestational age at birth | ||||||||
| 37–41 | 1 | – | 1 | – | ||||
| <37 | 1.80 (1.39–2.33) | <0.001 | 1.43 (1.06–1.92) | 0.01 | ||||
| >41 | 1.49 (0.85–2.61) | 0.16 | 1.13 (0.61–2.07) | 0.68 | ||||
In individuals with ABG acidosis, 51 babies had VBG acidosis, 5 babies had hypoxia VBG, and 1417 babies were normal [Figure 1].
Figure 1.
Percentage of VBG PH levels in infants with acidic ABG PH
Discussion
According to the findings, a significant relationship was observed between some characteristics of the mother and newborn with different levels of ABG, and also, the odds of acidic and hypoxic ABG levels were higher in mothers with fetal distress, gestational weeks <37 weeks, and mothers with gestational diabetes treated with insulin.
Similar to our study, the results of the study by Heydarzadeh et al.[19] showed that there is a significant relationship between umbilical cord blood pH and birth weight, gestational age, first- and fifth-minute Apgar score, need for advanced resuscitation, incidence of asphyxia, and complications. The findings of Tiia-Marie Sundberg et al.[20] showed that large differences between umbilical cord venous and arterial pH were strongly associated with a lower relative risk for Apgar < 7 at 5 minutes, need for CPAP, and NICU admission. In the study of Bordbar et al.[21] on 116 infants, the results showed that there was a significant relationship between the Apgar score of the first minute and the Apgar score of the fifth minute and arterial PH.
The study of Zaigham et al.[4] showed that in mothers with normal delivery and under induction compared to elective cesarean section, the mother’s underlying disease, such as high blood pressure and anemia, has a statistically significant relationship with the acidic level of PH ABG, which was consistent with our study.
In this study, the COVID-19 disease had a significant relationship with the impaired level of PH ABG, which is consistent with the study of Sobkowski et al.[22] born to SARS-CoV-2-infected mothers presented with worse conditions at 1 and 5 minutes of life and lower Arterial Blood Gas—ABG pH scores.
In our study, the number of boy infants with hypoxia umbilical cord blood pH level was higher, but gender was not statistically significant, which can be justified by the study of Finnstrom et al.[23] who identified the increase of hypoxia in boy infants as a genetic factor.
Mintzer et al.[24] found a correlation between low birth weight and cord blood gas acidosis levels. In our study, a significant relationship was observed between different levels of ABG and the birth weight of the newborn.
In Modarres Nejad’s study, logistic regression analysis showed that fetal distress had a highly significant relationship with acidemia, and the risk of acidemia in neonates with fetal distress was 7.7 times higher than in neonates without fetal distress.[25] In the present study, the odds of ABG acidemia and hypoxia in mothers with fetal distress were 3.51 and 2.30 times that of mothers without fetal distress.
In the results of multivariate regression analysis, a significant relationship was observed between gestational diabetes with insulin consumption and ABG acidemia and hypoxia levels (GDM, Insulin, OR = 5.08; and OR = 2.48). The Augustine et al.[26] study results showed that the offspring of gestational diabetic mothers present significant differences in pO2 and pCO2 when compared to normal fetuses at delivery. A study conducted by Jahromi et al.[27] observed the neonatal umbilical artery blood gas values between offspring of the diabetic mothers and normal mothers, which showed higher pCO2 values in the neonates of the diabetic mothers when compared with the control group. Since gestational diabetes is associated with important changes in the structure, development and function of the placenta, studies have shown that in chronic conditions of placental insufficiency such as gestational diabetes and preeclampsia, unfavorable blood flow of the placenta to the fetus and weak gas exchange between the placenta and the fetus, it can lead to chronic fetal hypoxia followed by fetal acidosis.
The odds of acidic and hypoxia ABG levels of mothers with gestational age <37 weeks are 2.25 and 1.43 times that of mothers with 37–41 weeks of gestation. A Swedish study of 27,175 infants showed a linear decrease in pH for cord arterial and venous blood with advancing gestational age.[4] Nicolaides et al.[28] demonstrated that in both the artery and vein, pH and pO2 decrease and pCO2 increases with advancing gestational age.
One of the main strengths of the present study was the large sample size, and that blood sampling was performed by trained professionals. In addition, all blood gas samples were analyzed immediately after preparation with the help of a blood gas analyzer located in the labor and delivery department of the hospital. Maternal and neonatal data were also entered into the study database directly after delivery. In this study, information about the mother’s physical and nutritional activities was not investigated, which can affect the mother’s metabolic status and pregnancy outcomes.
Limitations and Recommendations
In this study, information regarding maternal physical activity and nutritional habits was not examined, which could influence the maternal metabolic status and pregnancy outcomes.
Conclusion
In the present study, there was a significant relationship between the decrease in the pH of the umbilical cord artery and vein with preterm birth, IUGR, history of abortion, emergency cesarean section, labor with induction, gestational diabetes, diabetes, preeclampsia, eclampsia, HTN, anemia, addiction, and COVID-19. Umbilical cord acidosis can lead to neonatal complications. Therefore, it can be concluded that the measurement of umbilical cord blood gases is a useful tool to check newborns at risk.
Ethical code
The study was approved by the Ethics Committee of Shahid Beheshti University of Medical Sciences with the code (IR.SBMU.MSP.REC.1401.659).
Author’s contributions
MT and RN: Conceptualization, RN and SA: Data curation, TV and NA: Formal analysis, SOK, NA, RN and TV: Methodology, SOK, MT, SA and NA: first draft writing, All authors: Review and editing. All authors had full access to all the data in the study and had final responsibility for the decision to submit for publication.
Conflicts of interest
There are no conflicts of interest
Funding Statement
Nil.
References
- 1.Gardner DS, Giussani DA. Enhanced umbilical blood flow during acute hypoxemia after chronic umbilical cord compression: A role for nitric oxide. Circulation. 2003;108:331–5. doi: 10.1161/01.CIR.0000080323.40820.A1. [DOI] [PubMed] [Google Scholar]
- 2.Lee JH, Jung J, Park H, Kim SY, Kwon DY, Choi SJ, et al. Umbilical cord arterial blood gas analysis in term singleton pregnancies: A retrospective analysis over 11 years. Obstet Gynecol Sci. 2020;63:293–304. doi: 10.5468/ogs.2020.63.3.293. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Cai Y, Zhang X, Wu X, Liu H, Qi L, Liu X. The value of umbilical artery blood gas analysis in the diagnosis and prognosis evaluation of fetal distress. Am J Transl Res. 2022;14:4821–9. [PMC free article] [PubMed] [Google Scholar]
- 4.Zaigham M, Helfer S, Kristensen KH, Isberg PE, Wiberg N. Maternal arterial blood gas values during delivery: Effect of mode of delivery, maternal characteristics, obstetric interventions and correlation to fetal umbilical cord blood. Acta Obstet Gynecol Scand. 2020;99:1674–81. doi: 10.1111/aogs.13936. [DOI] [PubMed] [Google Scholar]
- 5.Ferreira CS, Melo Â, Fachada AH, Solheiro H, Nogueira Martins N. Umbilical cord blood gas analysis, obstetric performance and perinatal outcome. RBGO Gynecol Obstet. 2018;40:740–8. doi: 10.1055/s-0038-1675187. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Sharbaf FR, Amjadi N, Alavi A, Akbari S, Forghani F. Normal and indeterminate pattern of fetal cardiotocography in admission test and pregnancy outcome. J Obstet Gynaecol Res. 2014;40:694–9. doi: 10.1111/jog.12226. [DOI] [PubMed] [Google Scholar]
- 7.Sabol BA, Caughey AB. Acidemia in neonates with a 5-minute apgar score of 7 or greater–what are the outcomes? Am J Obstet Gynecol. 2016;215:486. doi: 10.1016/j.ajog.2016.05.035. e1-6. [DOI] [PubMed] [Google Scholar]
- 8.Knutzen L, Svirko E, Impey L. The significance of base deficit in acidemic term neonates. Am J Obstet Gynecol. 2015;213:373. doi: 10.1016/j.ajog.2015.03.051. e1-373.e7. [DOI] [PubMed] [Google Scholar]
- 9.Kacho MA, Zahedpasha Y, Haghshenas M, Rad ZA, Nasseri BS, Bijani A. Short term outcome of neonates born with abnormal umbilical cord arterial blood gas. Iran J Pediatr. 2015;25:e174. doi: 10.5812/ijp.25(3)2015.174. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Georgieva A, Moulden M, Redman CW. Umbilical cord gases in relation to the neonatal condition: The EveREst plot. Eur J Obstet Gynecol Reprod Biol. 2013;168:155–60. doi: 10.1016/j.ejogrb.2013.01.003. [DOI] [PubMed] [Google Scholar]
- 11.Ghomian N, Abardeh AM, Darbari SM, Bagheri H. Diagnostic value of arterial blood gas indices in predicting early neonatal complications. Sci J Kurdistan Univ Med Sci. 2021;26:105–16. [Google Scholar]
- 12.Kohan S, Hajihashemi M, Valiani M, Beigi M, Mohebbi-Dehnavi Z. Maternal-infant outcomes of birth planning: A review study. J Educ Health Promot. 2023;12:315. doi: 10.4103/jehp.jehp_1450_22. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Malin GL, Morris RK, Khan KS. Strength of association between umbilical cord pH and perinatal and long term outcomes: Systematic review and meta-analysis. BMJ. 2010;340:c1471. doi: 10.1136/bmj.c1471. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Hantoushzadeh S, Sheikh M, Bosaghzadeh Z, Ghotbizadeh F, Tarafdari A, Panahi Z, et al. The impact of gestational weight gain in different trimesters of pregnancy on glucose challenge test and gestational diabetes. Postgrad Med J. 2016;92:520–4. doi: 10.1136/postgradmedj-2015-133816. [DOI] [PubMed] [Google Scholar]
- 15.Masoudi Z, Kasraeian M, Akbarzadeh M. Assessment of educational intervention and Acupressure during labor on the mother’s anxiety level and arterial oxygen pressure of the umbilical cord of infants (PO2). A randomized controlled clinical Trial. J Educ Health Promot. 2022;11:86. doi: 10.4103/jehp.jehp_685_20. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Aalipour S, Hantoushzadeh S, Shariat M, Sahraian S, Sheikh M. Umbilical cord blood acidosis in term pregnancies with gestational diabetes mellitus and its relations to maternal factors and neonatal outcomes. Iranian Red Crescent Med J. 2018;20:e59267. [Google Scholar]
- 17.James L, Weisbrot I, Prince C, Holaday D, Apgar V. The acid-base status of human infants in relation to birth asphyxia and the onset of respiration. J Pediatr. 1958;52:379–94. doi: 10.1016/s0022-3476(58)80058-x. [DOI] [PubMed] [Google Scholar]
- 18.Lassi ZS, Middleton PF, Crowther C, Bhutta ZA. Interventions to improve neonatal health and later survival: An overview of systematic reviews. EBioMedicine. 2015;2:985–1000. doi: 10.1016/j.ebiom.2015.05.023. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Heidarzadeh M, Fayyazi A, Abdollahi-Fard S, Soflaei ZG, Shabanloei R, Ahmadi F, et al. Relationship between blood cord analysis at delivery time and outcome of resuscitated neonates. Med J Tabriz Univ Med Sci. 2010;32:27–32. [Google Scholar]
- 20.Sundberg TM, Wiberg N, Källén K, Zaigham M. Adverse neonatal outcome and veno-arterial differences in umbilical cord blood pH (ΔpH) at birth: A population-based study of 108,629 newborns. BMC Pregnancy Childbirth. 2023;23:162. doi: 10.1186/s12884-023-05487-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Bordbar A, Kashaki M. The relationship between umbilical artery blood gas analysis and apgar scores in neonates. Razi J Med Sci. 2020;27:68–74. [Google Scholar]
- 22.Sobkowski M, Pięta B, Sowińska A, Grabowska M, Koch-Brzozowska K, Wilczak M, et al. SARS-CoV-2 in pregnancy – A retrospective analysis of selected maternal and fetal laboratory parameters. Int J Environ Res Public Health. 2022;19:15307. doi: 10.3390/ijerph192215307. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Finnström O. A genetic reason for male excess in infant respiratory mortality? Acta Paediatr. 2004;93:1154–5. doi: 10.1080/08035250410014854. [DOI] [PubMed] [Google Scholar]
- 24.Mintzer JP, Messina C. Cerebral oxygenation during umbilical arterial blood sampling in very low birth weight neonates. J Perinatol. 2018;38:368–73. doi: 10.1038/s41372-017-0034-2. [DOI] [PubMed] [Google Scholar]
- 25.Modarressnejad V. Umbilical cord blood Ph and risk factors for acidaemia in neonates in kerman. East Mediterr Health J. 2005;11:96–101. [PubMed] [Google Scholar]
- 26.Sreedharan R, Augustine G, Sampson U, T. K J, Manikumar R. Evaluation of umbilical cord arterial blood gas analysis in gestational diabetes mellitus. Indian J Clin Anat Physiol. 2020;5:508–14. [Google Scholar]
- 27.Jahromi BN, Ahmadi N, Cohan N, Jahromi MR. Comparison of the umbilical artery blood gas, nucleated red blood cell, C-reactive protein, and white blood cell differential counts between neonates of diabetic and nondiabetic mothers. Taiwan J Obstet Gynecol. 2011;50:301–5. doi: 10.1016/j.tjog.2011.01.029. [DOI] [PubMed] [Google Scholar]
- 28.Nicolaides KH, Economides DL, Soothill PW. Blood gases, pH, and lactate in appropriate- and small-for-gestational-age fetuses. Am J Obstet Gynecol. 1989;161:996–1001. doi: 10.1016/0002-9378(89)90770-9. [DOI] [PubMed] [Google Scholar]