Worldwide, of the 130 million neonates born every year, 15 million neonates are born preterm. Moreover, prematurity is still a major cause of neonatal and infant mortality and morbidity and a significant contributor to long-term adverse health outcomes [1, 2]. About 123.13% of preterm births at 32 to less than 37 weeks of gestation are reported in Egypt. This statistic may indicate a higher rate of admission to the NICU every year [3]. A study by Algameel et al. [4], conducted in Upper Egypt, indicated that 28% of the studied neonates were late preterm infants.

Infants born preterm have a higher risk for mortality, as indicated by a study conducted in low and middle-income countries [5]. This greater risk for mortality has frequently been pertaining to neonatal sepsis [6]. Moreover, they have a higher risk for short- and long-term complications, such as neurological, cognitive, and motor disorders. Likewise, they are more prone to malnutrition, chronic illnesses, and early death [7].

The delivery of preterm infants has been linked to many factors. Studies conducted by Kildea et al. [8] and Savitz and Murnane [9] found that ethnicity, mothers' age, and smoking are risk factors for preterm birth. Others identified that mothers' education is also a risk factor for preterm birth [10-12]. Whereas Delnord et al. [13] reported that mothers' parity is a risk factor for preterm birth. Additionally, lack of antenatal care leads to poor pregnancy outcomes, such as preterm births [14].

Moreover, Gurung et al. [15] determined that mothers' age, education, smoking habits, lack of antenatal care, multiple deliveries, and severe anemia are risk factors for preterm birth. Besides, other studies revealed that interventions, such as labor induction and cesarean section (C.S), attributed to preterm birth [16, 17]. Hosnya et al. [18] found that factors like mothers' age, history of abortion, antepartum bleeding, prenatal infection, and premature rupture of membranes (PROM) are prominent factors for preterm birth.

There are many factors that indicate the admission of preterm infants to NICU, such as respiratory distress syndrome (RDS), feeding difficulties, apnea, neonatal jaundice (NJ), necrotizing enterocolitis (NEC), hypoglycemia, neonatal sepsis (NS), intraventricular hemorrhage (IVH), and temperature instability [19]. Despite care at NICU, immaturity at birth has a lifelong impact on various systems [19], disabilities, and delayed neurodevelopment, such as learning, hearing, and visual complications [20]. Moreover, a short-term impact increases with decreasing gestational age [21]. Therefore, detecting and interpreting the risk factors, indications of admission, and outcomes for prematurity can aid in identifying this problem.

Fig. (1) indicates that 49.4% were preterm infants and 50.6% were full-term neonates.

Fig. (1). Incidence of preterm infants among neonatal admissions (N=1400).

Fig. (2). Gestational age/week of preterm infants (n=692).

Fig. (2) shows that 26.5% of preterm infants were born at 36 weeks. Moreover, 20.7% and 20.5% of them were born at 34-<36 and <30 weeks, respectively. The mean gestational age was 32.53±3.05.

Table 1 reveals that 60.8% were males, and 78.2% were born in a single gestation. Moreover, 40.6 were delivered by emergency C.S. Furthermore, 52.3% of mothers were aged 20-<30 years old, and 75.7% of them were not working. Moreover, there were statistically negative correlations between the type of gestation (r=-0.2, p=0.000) and mothers' age (r=-0.1, p=0.001) with the gestational age of preterm infants.

Fig. (3) illustrates that 48.1% of admitted preterm infants died while 51.9% of them were stable on discharge with a statistically negative correlation (r=-0.3, p=0.000).

Table 2 demonstrates statistically positive correlations regarding family history of medical diseases (r=0.4, p=0.000*) and mothers' history of medical diseases (r=0.1, p=0.000*) with the gestational age of preterm infants. While there were no statistically negative correlations regarding mothers' gravidities, parity, and abortion numbers (r=-0.01, p=0.6, and r=-0.03, p=0.4, r=-0.01, p=0.6) respectively, and gestational age of preterm infants.

Table 3 detects statistically significant differences concerning mothers' complications during current pregnancy; anemia (p=0.01*), PIH (0.001*), preeclampsia (p=0.02*), APH (0.01*), PROM (p=0.000*), and obstructed labor (p=0.000*) and gestational age of preterm infants.

Table 4 identifies respiratory problems as the main etiology for preterm infants' NICU admission; 28.9% and 28.3% were RDS and RD, respectively. Followed by gastrointestinal; POI and NJ were 22.5% and 14.2%, respectively, CA were 16.6%, neurological causes; poor reflexes were 13.9%, and NS was 13.8%.

Fig. (3). Discharge outcome of preterm infants (n=692).

The largest number of developing countries lack reliable data on the incidence of preterm labor [2]. Therefore, this study aimed to define the incidence of preterm infants' admission at the neonatal Intensive Care Unit, indications, risk factors, and discharge outcome.

This retrospective study found a higher incidence (49.4%) of admitted neonates at the NICU that were born preterm; of 1400 high-risk neonates, 692 were born preterm. This finding was supported by the study conducted by Khasawneh et al. [22] in Jordan, who found that 56% of preterm births required admission to NICU. Moreover, Khasawneh et al. [23] indicated that the main indication for NICU admission was prematurity, representing 33.3% among the whole study cohort. Likewise, Abdelhady and Abdelwahid [3] revealed a higher admission rate of preterm neonates from 32 to less than 37 weeks. Moreover, a study conducted by Kuppusamy and Vidhyadevi [19] found that 28.25% of the total NICU admission were preterm infants. The higher incidence in this study could be due to the higher admissions of high-risk neonates to the NICU than other intermediate care units for neonates. Besides, this NICU is the main NICU in Upper Egypt and receives many referrals, leading to higher admission rates. Therefore, this demonstrates that preterm birth is a significant health problem.

Additionally, it was noticed that more than one-fourth of the studied preterm infants were born at 36 weeks with a mean gestational age of 32.53±3.05. This result was in the same line with the findings of studies conducted by Abdel Razeq et al., Al-Qurashi et al., and Abdelhady and Abdelwahid [3, 24, 25]. Moreover, Khasawneh and Khriesat [23] found that late preterm at 36 weeks of gestation accounted for a higher rate (75%) of NICU admission among all premature births. This result might be demonstrated by increasing use of assisted reproduction, higher rates of labor induction, and increased rates of C.S delivery.

The present study found statistically negative correlations between the type of gestation and gestational age of preterm infants, indicating that mothers who had multiple gestations were more prone to deliver preterm. This finding was in the same line with the findings of Gurung et al. [15] and Kuppusamy and Vidhyadevi [19], where they found that multiple gestations were significant risk factors of preterm birth. Other studies done in Korea by Kim et al. [26] and in Bangladesh by Shah et al. [27] demonstrated the same results. This finding could be attributed to the fact that multiple gestations cause distension of the uterus, leading to early labor.

Moreover, statistically negative correlations between mothers' age and gestational age of preterm infants showed that the mothers' age is a significant factor that increases the risk of delivery of a preterm infant. This result was reinforced by the findings of Gurung et al. [15], who indicated that preterm births are higher among younger mothers. Numerous other studies also reported an association between younger and older mothers and preterm birth [28-31]. This result might be attributed to younger mothers having less experience concerning pregnancy complications and outcomes. In comparison, older ones might have health risk factors.

Moreover, it was observed that nearly half of the studied sample was dead on discharge. This was supported by the findings of Gurung et al., Sania et al., and Draper et al. [15, 32, 33]. Moreover, KC et al. [34] found a 12-fold increased risk of neonatal death among preterm infants compared to full-term. This higher incidence of mortality rate among the studied preterm infants might be due to the higher frequency of very (<32 weeks) and extremely (<28 weeks) preterm infant incidence.

The study reported statistically positive correlations between family history of medical diseases and mothers' history of medical diseases with preterm infants' gestational age. These findings were in agreement with the findings of studies conducted by Aregawi et al., Ticaria et al., and Mohsenzadeh et al. [35-37], who found that maternal medical complications as chronic diseases are a risk factor for preterm birth. These findings could be due to the major adverse effects of medical diseases on mothers' health in general and in pregnancy specifically.

Furthermore, the study determined that mothers who had anemia, PIH, preeclampsia, APH, PROM, and obstructed labor during pregnancy are more at risk for preterm birth. These results were concurrent with many studies conducted by Hosnya et al., Gurung et al., Aregawi et al., and Wagura et al. [2, 15, 18, 35], who found that PIH, APH, and PROM are significant risk factors for preterm labor. Likewise, the results by Kuppusamy and Vidhyadevi [19] revealed that anemia, PROM, and PIH are the most common associated factors for prematurity. Moreover, Mohsenzadeh et al. [37] indicated that PROM and preeclampsia are significant risk factors for preterm birth. Moreover, a study conducted in Egypt by El Beltagy et al. [38] had the same results. The researchers agreed that these findings were due to the direct negative effects of these complications on mothers' health during pregnancy and, therefore, on the health of the fetus.

Finally, the study findings identified that respiratory causes are the main etiology for preterm infants' NICU admission as RDS and RD, followed by gastrointestinal poor oral intake and NJ, CA, neurological problems, such as poor reflexes, and NS. These results were similar to the results of Khasawneh and Khriesat [23], who demonstrated that preterm infants had higher rates of RDs and sepsis. Moreover, a study by Algameel et al. [4] conducted in Upper Egypt found that jaundice and respiratory morbidity were increased among preterm infants. These results could be due to premature birth; the neonates had immature lungs and lacked sufficient surfactant for normal lung expansion, leading to a higher frequency of RD and RDs.

The limitation of this study is the retrospective design where all the inferred data reflect what is recorded and reported in the medical records. Thus, specific outcomes might be overestimated or underestimated. Although this study was conducted at a large university hospital, the findings cannot represent the whole Egyptian population; therefore, a conclusion about the generalizability of the findings cannot be accurately made.

A higher prevalence with a higher mortality rate of admitted preterm infants to NICU was reported. Likewise, the type of gestation, mothers' age, presence of complications during pregnancy, bad obstetric history, and family and medical history of diseases were found to be the most common risk factors of prematurity. Moreover, respiratory problems were the main etiology for admission of preterm infants to NICU. Therefore, early screening of diseases and obstetric complications during pregnancy is recommended.

Following strategies can be recommended:

• Raising public and professional health awareness of the risk factors linked to prematurity.
• Implementing educational programs for early detection and intervention for short-term and long-term complications.
• Local strategies and policies should be established and implemented to improve the outcome of birth through early screening of diseases and obstetric complications.
• Increasing mothers' awareness about the importance of antenatal care and follow-up. Therefore, early detection and intervention of complications can be done.