In 2010, the World Health Organization reported that the cesarean delivery rate in China had reached 46.2%, of which 11.7% were performed without a clear indication. While efforts are being made to reduce the number of cesarean deliveries without medical indications, the timing of cesarean delivery is also receiving increasing attention. Choosing the “good time” is not only the reason why many pregnant women choose to have cesarean delivery, but also an important factor affecting the timing of cesarean delivery. Every year in late August and around the Lunar New Year, a large number of pregnant women choose to have a cesarean delivery during this period for non-medical reasons. Improper timing of cesarean delivery will increase adverse neonatal outcomes. Therefore, this paper discusses the timing of cesarean delivery. The timing of elective cesarean delivery has been described in the form of guidelines or recommendations in several countries. In 2004, the National Institute of Health and Clinical Excellence (NICE) of the United Kingdom published a clinical guideline on cesarean delivery. In 2011, NICE revised its clinical guideline on cesarean delivery, but the recommendations on the timing of elective cesarean delivery remained unchanged. The National Institute of Health (NIH) and the American College of Obstetricians and Gynecologists (ACOG) stated in 2007 that cesarean delivery at the mother’s request should not be performed before 39 weeks of gestation, Unless there is evidence of fetal lung maturation. Gurol-Urganci et al. reviewed elective cesarean deliveries in 63 English hospitals affiliated with the National Health System (NHS) from 2000 to 2009 and found that elective cesarean deliveries after 39 weeks of gestation increased steadily from 39% in 2000 to 2001 to The proportion of cesarean deliveries performed after 39 weeks of gestation increased from 43% to 67%, and the proportion of repeat cesarean deliveries increased from 35% to 62%. This suggests that the timing of elective cesarean delivery has changed significantly since the introduction of the NICE guideline. However, within the NHS, the timing of cesarean delivery still varies considerably between hospitals. This study therefore concluded that the timing of elective cesarean delivery should be used and monitored as an obstetric quality assessment criterion to change clinical practice and delay elective cesarean delivery. Clark et al. in the United States suggested that through education and policy implementation, it should be possible to increase the rate of elective deliveries after 39 weeks of gestation to 95% in the United States. In China, there are no guidelines or recommendations for the timing of elective cesarean delivery. According to our incomplete statistics, pregnant women with combined gestational diabetes usually undergo elective cesarean delivery between 39 and 40 weeks of gestation; other pregnant women, such as those with breech position, pelvic factors, and a history of previous cesarean deliveries, often choose to undergo elective cesarean delivery between 38 and 39 weeks of gestation. There are also a significant number of pregnant women who request “day” or even “time” cesarean delivery due to social factors. Despite the controversy, there is an international preference for elective cesarean delivery between 39 and 40 weeks of gestation to reduce neonatal respiratory morbidity. In the 1990s, many studies showed that elective cesarean delivery before 39 weeks of gestation was associated with neonatal respiratory disease and increased the likelihood of neonatal transfer to the neonatal intensive care unit (NICU), leading to increased medical costs and psychological problems associated with the separation of mother and child. Psychological problems. The incidence of neonatal respiratory distress syndrome can be reduced to 1 in 10,000 if elective cesarean delivery is performed after 39 weeks of gestation, and a growing body of research in the 21st century has found that medically induced preterm delivery is a major cause of severe neonatal respiratory disease and that elective cesarean delivery at any gestational age may result in transient respiratory distress and persistent pulmonary hypertension in the newborn. In January 2009, the New England Journal of Medicine published the results of the largest multicenter, prospective clinical study to date, which analyzed data on repeat cesarean deliveries in singleton pregnancies at 19 clinical centers in the United States from 1999 to 2002. After excluding the cases of multiple pregnancies and early termination of pregnancy due to comorbidities, the distribution of elective cesarean delivery was 6.3% at 37 weeks of gestation, 29.5% at 38 weeks of gestation, and 49.1% at 39 weeks of gestation. The incidence of adverse neonatal outcomes decreased significantly with the time of termination (15.3% at 37 weeks of gestation and 8.0% at 39 weeks of gestation). At 40 weeks of gestation, there was a trend toward an increase in the number of major adverse neonatal outcomes (respiratory complications, sepsis, death, need for NICU transfer, and prolonged hospital stay), but the number of cases was low. This study suggests that unless there is evidence of fetal lung maturation, elective cesarean delivery should be performed after 39 weeks of gestation in the absence of specific maternal and fetal indications. The study was selected because the timing of repeat cesarean delivery has become an increasingly prominent issue as the number of vaginal birth after previous cesarean delivery (VBAC) declines and the rate of cesarean delivery in the United States increases. The timing of repeat cesarean delivery is usually earlier than the initial elective cesarean delivery, so the results of the study are also instructive for the initial cesarean delivery. In 2011, Peking Union Medical College Hospital was the first hospital in China to analyze the pregnancy outcomes of women who had elective cesarean delivery. The study retrospectively analyzed 8716 full-term elective cesarean deliveries from 2002 to 2009 (93% of primigravida), and after excluding pregnant women who underwent cesarean delivery due to severe medical comorbidities, 4565 and 409 underwent initial and repeat cesarean deliveries, respectively. The study obtained similar results to those of Tita et al. that elective cesarean delivery at 39 weeks of gestation reduces perinatal morbidity and mortality in newborns, both for initial and repeat cesarean deliveries. The study also showed that maternal morbidity and hemorrhage did not increase significantly with increasing gestational weeks. In contrast, initial elective cesarean delivery after 40 weeks of gestation was associated with an increase in adverse neonatal outcomes. Because the study was a single-center retrospective study with an inadequate sample size, many of the differences in outcomes were not statistically significant, such as only 14 repeat elective cesarean deliveries after 40 weeks of gestation, which was not statistically significant for analysis and did not evaluate the stillbirth rate, which is a limitation. Because according to the calculation of Tita et al. 20,000 cases were studied to assess the event rate of 0.1% to 1.0%. Although the timing of elective cesarean delivery has been described in the form of guidelines or recommendations in several countries and is supported by a large number of studies, some scholars do hold different opinions. They argue that the choice of elective cesarean delivery at 39 weeks of gestation is based on neonatal outcomes, especially respiratory complications, but ignores other issues. First, 10%-14% of pregnant women will deliver spontaneously at 38-39 weeks of gestation, turning a significant number of elective cesarean deliveries into emergency procedures, a population that has been excluded from most of the available studies, leading to an underestimation of surgical complications.In a cohort study by Hansen et al, a significant reduction in neonatal respiratory morbidity was found with elective cesarean delivery at 39 weeks of gestation. However, 25% of the pregnancies were delivered before 39 weeks of gestation, which may increase the risk of uterine rupture, infection, and peripheral organ damage. In fact, as early as 2003, it was suggested that ultrasound measurements of cervical length should be performed at 37 weeks of gestation to assess the likelihood of spontaneous delivery before 40 weeks of gestation and to help choose the timing of cesarean delivery. The next issue is stillbirth and stillbirth. The incidence of stillbirth at 33 to 39 weeks of gestation is 0.6 per 1000 live births, while after 39 weeks, this rate increases to 1.9 per 1000 live births. In a large sample of women with a history of previous cesarean delivery, the stillbirth rate was 0.2 and 0.5 per 1000 live births at 37 and 38 weeks of gestation, respectively. The chance of stillbirth increases with the duration of pregnancy. Again, older women are more likely to choose cesarean delivery as a method of pregnancy termination. This group has a higher incidence of perinatal complications. Even if intrauterine death due to fetal malformation is excluded, the probability of intrauterine death is still higher in older than in younger women. They also have a higher incidence of complications when undergoing emergency cesarean delivery. Therefore, some scholars believe that elective cesarean delivery should be advanced to 38 weeks of gestation for pregnant women with a history of multiple cesarean deliveries or advanced age, and that providers should decide whether to perform elective cesarean delivery after 39 weeks of gestation based on their ability to perform emergency cesarean delivery. Compared with singleton pregnancies, twin pregnancies are more likely to have maternal and fetal complications, especially the incidence of preterm delivery and intrauterine death, which is significantly higher than that of singleton pregnancies. Therefore, the timing of elective cesarean delivery in twin pregnancies is more complex and involves more factors, and there are fewer studies on the timing of elective cesarean delivery in twin pregnancies, and there are no recommendations from ACOG or NICE in this regard. Risk factors included maternal age >25 years, preterm delivery, and emergency cesarean delivery. Breathnach et al. concluded that uncomplicated single-chorionic twins could be terminated after 37 weeks of gestation with close fetal monitoring, while double-chorionic twins could be extended to 38 weeks of gestation. To date, no randomized controlled studies with elective cesarean delivery at 38 weeks of gestation or 39 weeks of gestation with concomitant analysis of maternal and child outcomes have been identified. In China, there are few studies on the timing of cesarean delivery and there are no corresponding guidelines. Therefore, in the absence of other medical indications, elective cesarean delivery between 39 and 40 weeks of gestation is a reasonable option. It is expected that multicenter and prospective collaborative studies will be conducted in China in the future to obtain results suitable for the Chinese population.