The association between induction of labour in nulliparous women at term and subsequent spontaneous preterm birth: a retrospective cohort study.

OBJECTIVES: To evaluate the rate of subsequent spontaneous preterm birth in patients with previous induction of labour at term compared to women with previous spontaneous labour at term. METHODS: This was a retrospective cohort study of all women with consecutive births at the Royal Brisbane and Women's Hospital between 2014 and 2018. All nulliparous women with a singleton pregnancy and induction of labour at term or in spontaneous labour at term in the index pregnancy were included. Data was extracted from electronic medical records. The outcome of spontaneous preterm birth in the subsequent pregnancy was compared between patients with previous term induction of labour and in previous term spontaneous labour. RESULTS: A total of 907 patients with consecutive births met the inclusion criteria; of which 269 (29.7%) had a term induction of labour and 638 (70.3%) had a term spontaneous labour in the index pregnancy. The overall subsequent spontaneous preterm birth rate was 2.3%. Nulliparous women who underwent term induction of labour were less likely to have a subsequent preterm birth compared to nulliparous women in term spontaneous labour (0.74 vs. 2.98%; odds ratio [OR], 0.25; 95% confidence interval, 0.06-1.07; p=0.0496) in the index pregnancy. This however was not significant once adjusted for confounders (adjusted OR, 0.29; p=0.10). Spontaneous preterm birth was associated with a previous spontaneous labour compared to induction of labour between 37 to 37+6 and 38 to 38+6 weeks (adjusted OR 0.18 and 0.21; p=0.02 and 0.004 respectively). CONCLUSIONS: Term induction of labour does not increase the risk of subsequent spontaneous preterm birth compared to spontaneous labour at term in nulliparous women. Further research is needed to validate these findings in a larger cohort of women and to evaluate the effect of elective IOL among low-risk nulliparous women.

The risk of preterm delivery and pregnancy outcomes in women with asymptomatic short cervix: a retrospective cohort study.

OBJECTIVE: Routine cervical length measurement in asymptomatic pregnant women to prevent preterm birth has not been universally adopted due to poor predictive accuracy. The purpose of our study was to evaluate the risk of preterm delivery and pregnancy outcomes in women with asymptomatic short cervix and examine the implications of gestational age at presentation on these outcomes. STUDY DESIGN: This was a retrospective cohort study of women with singleton pregnancies who presented prior to or at 32 + 0 weeks with an asymptomatic short cervix (≤25 mm) between April 2014 to March 2018 at a single tertiary maternity center. Women with cervical length ≤25 mm were grouped into four cohorts according to gestational age at presentation: Obstetric outcomes were compared between the cohorts and the general cohort of women delivering during the same period. Outcomes were compared using Mann-Whitney U, chi-square tests, and logistic regression. Survival analysis was carried out to compare the probability of delivery for each subgroup. RESULTS: The rate of spontaneous preterm birth <37 weeks was highest in the cohort presenting at 25 + 0-27 + 6 weeks, and lowest in the first cohort presenting at <22 + 0 (60.0 versus 22.2%, p < .05). When compared with the general cohort, the rate of spontaneous preterm birth at <37-week gestation was significantly higher in the asymptomatic short cervix cohort (40.4 versus 8.7%, p < .001), with a 7.1-fold increase in the relative risk of spontaneous PTB. CONCLUSIONS: In asymptomatic women, cervical shortening showed significant increase in the risk of preterm birth. Our study findings suggest that routine cervical screening may be helpful in predicting risk of preterm birth even in women who are considered low-risk for preterm birth.

Does the length of second stage of labour or second stage caesarean section in nulliparous women increase the risk of preterm birth in subsequent pregnancies?

OBJECTIVES: This study aimed to investigate the role of prolonged second stage of labour and second stage caesarean section on the risk of spontaneous preterm birth (sPTB) in a subsequent pregnancy. METHODS: This was a retrospective cohort study of nulliparous women with two consecutive singleton deliveries between 2014 and 2017 at a tertiary centre. In the vaginal delivery cohort, subsequent pregnancy outcomes for women with a prolonged second stage (>2 h) were compared with those with a normal second stage (≤2 h). In the caesarean delivery cohort, women with a first stage or a second stage were compared with the vaginal delivery cohort. The primary outcome was subsequent sPTB. RESULTS: A total of 821 women met inclusion criteria, of which 74.8% (614/821) delivered vaginally and 25.2% (207/821) delivered by caesarean section. There was no association between a prolonged second stage in the index pregnancy and subsequent sPTB (aOR 0.70, 95% CI 0.13-3.83, p=0.7). The risk of subsequent sPTB was threefold for those with a second stage caesarean section; however this did not reach statistical significance. CONCLUSIONS: A prolonged second stage of labour in the index pregnancy is not associated with an increased risk of subsequent sPTB. A second stage caesarean section in the index pregnancy may be associated with an increased risk of subsequent sPTB, however there was no statistically significant difference. These findings are important for counseling and suggest that the effects of these factors are not clinically significant to justify additional interventions in the subsequent pregnancy.