The study describes the incidence, risk factors and consequences associated with preterm births based on data available from 12 public hospitals across Nepal. The incidence of preterm births was found to be 9.8% among total births while it was 9.3% among live births. In a systematic review conducted with data available from 107 countries, the global preterm birth rate was reported at 10.6%  and a systematic analysis based on data available from 184 countries reported an estimated preterm births of 11.1% . Similarly, studies conducted in the United States (9.62%)  and Australia (8.6%)  have also reported similar estimates. A previous study conducted in a tertiary hospital in Nepal reported at incidence of 8.1% for preterm births . These findings suggest that Nepal’s preterm birth rate is in line with developed countries, suggesting an improvement over the national and global estimates.
The study looked at some of the potential risk factors for preterm births. The risk of preterm births was higher among mothers younger than 20 years. Several other studies have also reported linking both younger and older maternal age with preterm births [11,25–30]. However, a Bangladesh study found women aged <20 years to be protective for preterm, contrary to our findings . Our study did not find any significant association with mothers aged 35 years and above. The risk of preterm births was also higher among mothers with education lower than secondary level had a higher risk of having preterm births. Other studies have also shown similar associations related to lower education levels [14,16,20,31]. This suggests that better educational status of mothers has a direct effect on the birth outcomes. Further, mothers with a history of smoking had higher risk for preterm births. Other studies have also shown similar associations for preterm births [11,32–34]. Also, the risks were higher for mothers who did not use clean fuel. A recent study conducted in China showed no any significant association with the type of fuel used . However, another study conducted in East India looking at the impact of the fuels in pregnancy outcomes showed a significant association for preterm births . The variations could be due to the difference in sample sizes.
Our study showed that the risk was higher among nulliparous mothers. The findings have also been supported by previous studies [37,38]. Babies born to mothers who seek ANC visits during second and third trimesters also had a higher risk of being preterm. Seeking ANC visits later in pregnancies can increase the risks of preterm births, studies have shown [25,27,39]. Our study found that women who sought <4 ANC visits during pregnancy were at higher risk of giving preterm birth. A study conducted in rural Gambia also showed higher risk though the findings were not significant . Further, another study conducted by a Belgian team also found no substantial correlation between number of ANC visits and preterm birth but rather on the content and timing of care during pregnancy . Hence, ANC visits should focus on improved screening of at-risk pregnant women together with the ability to treat and manage infections and provide dietary support and counseling services .
The risk of preterm births was also higher among women who had severe anemia during pregnancy. The finding is corroborated by other studies which showed severe anemia increased the risk of preterm births significantly [42–44]. However, a study conducted in Tanzania showed no association with preterm birth, though the study only compared anemia without specifying the type and there were only 2 preterm birth cases . Further, mothers who had multiple deliveries had higher risk of having preterm births. A Korean study also showed similar associations . Another cohort study in Bangladesh also showed similar findings . However, a systematic review and meta-analyses assessing interventions aimed at preventing preterm births among twin pregnancies found that no interventions reduced the risk significantly .
The risk was also higher among women whose babies had major malformations although the association was not significant. However, previous studies have shown significant associations [48,49]. One of the reasons could be the low numbers reported from our study. Sex of the child had no any risks for preterm births. This was in line with another study who also showed no significant association between sex of the child and preterm births . However, several studies have linked male babies with preterm births [51–53].
We also analyzed the consequences of preterm birth. The pre-discharge mortality was 11-times higher for preterm babies. Other studies have also reported similar findings [24,54,55].
There are some limitations in the study. The study did not analyze some of the risk factors (e.g. previous medical history, previous preterm births, cervical length, BMI etc.) that have been discussed in the research articles as these data were either not collected in our study or they were underreported. Also, not all mothers took part in the interviews and for those who took part, the information might not be reliable due to recall bias. Further, we only analyzed pre-discharge mortality so we do not know about the consequences thereafter. Also, we did not collect data on other outcomes like birth-related injuries and other associated factors hence they are not reported in our study. Having said that, this is a large representative sample from 12 different hospitals. Hence, the results are a likely representation of the incidence of preterm births in Nepal.