[Analysis of adverse late-term pregnancy outcomes after cervical cold knife conization]

Objective: To investigate the effects of cervical cold knife conization (CKC) on preterm delivery, other pregnancy complications and neonatal outcomes, and explore the relationship between preterm delivery risk and the depth and volume of conization. Methods: The clinical data and pregnancy outcomes of 272 women who underwent CKC in Peking Union Medical College Hospital from January 2002 to March 2018 (conization group) and 1 647 pregnant women who gave birth in Peking Union Medical College Hospital during January to December 2019 (control group) were collected. The preterm delivery, premature rupture of membranes, other pregnancy complications and neonatal outcomes of the two groups were compared, and the relationship between the depth and volume of conization and the risk of preterm delivery in postoperative singleton pregnancy was analyzed. Results: (1) There were no significant differences between the two groups in delivery age, parity, proportion of singleton pregnancy, proportion of assisted reproductive technology (all P>0.05). (2) The rate of preterm delivery in the conization group was significantly higher than that in the control group [14.8% (39/264) vs 5.7% (91/1 589); χ²=28.397, P<0.001]. There were still significant differences in preterm delivery rates between the two groups at <34 weeks and 34-37 weeks (all P<0.01). There was no significant difference in the incidence of premature rupture of membrane between the two groups [23.5% (62/264) vs 23.4% (372/1 589); χ²=0.001, P=0.979], but the incidence of preterm premature rupture of membrane in the conization group was significantly higher than that in the control group [11.4% (30/264) vs 2.2% (35/1 589); χ²=56.132, P<0.001]. (3) The rate of cesarean section in the conization group was higher than that in the control group [59.6% (162/272) vs 38.8% (639/1 647); χ²=41.377, P<0.001]. The birth weight of preterm infants in the conization group was significantly higher than that in the control group [(2 409±680) vs (2 150±684) g; t=2.184, P=0.030]. However, there were no statistically significant differences in the incidence of gestational diabetes mellitus, hypertensive disorders in pregnancy, the birth weight of full-term infants, incidence of small for gestational age infant and neonatal intensive care unit admission rate between the two groups (all P>0.05). (4) The preterm delivery rates of coning depth >15 mm, cone size ≥2 cm³ and cone size <2 cm³ were higher than that in the control group (all P<0.05). When the coning depth ≤15 mm, the preterm delivery rate in the conization group was higher than that in the control group, but there was no significant difference (P=0.620). The rate of preterm delivery of pregnant women with coning depth >15 mm was significantly higher than those with coning depth ≤15 mm (RR=3.084, 95%CI: 1.474-6.453; P=0.001). There was no significant difference in the preterm delivery rate between pregnant women with cone size >2 cm³ and those with cone size ≥2 cm³ (RR=1.700, 95%CI: 0.935-3.092; P=0.077). Conclusion: The risk of preterm delivery and preterm premature rupture of membranes in subsequent pregnancies are increased after cervical CKC, and the risk of preterm delivery is positively correlated with the depth of cervical coning.