Prediction of spontaneous preterm birth in women with previous full dilatation cesarean delivery.

BACKGROUND: A previous term (≥37 weeks' gestation), full-dilatation cesarean delivery is associated with an increased risk for a subsequent spontaneous preterm birth. The mechanism is unknown. We hypothesized that the cesarean delivery scar characteristics and scar position relative to the internal cervical os may compromise cervical function, thereby leading to shortening of the cervical length and spontaneous preterm birth. OBJECTIVE: This study aimed to determine the relationship of cesarean delivery scar characteristics and position, assessed by transvaginal ultrasound, in pregnant women with previous full-dilatation cesarean delivery with the risk of shortening cervical length and spontaneous preterm birth. STUDY DESIGN: This was a single-center, prospective cohort study of singleton pregnant women (14 to 24 weeks' gestation) with a previous term full-dilatation cesarean delivery who attended a high-risk preterm birth surveillance clinic (2017-2021). Women underwent transvaginal ultrasound assessment of cervical length, cesarean delivery scar distance relative to the internal cervical os, and scar niche parameters using a reproducible transvaginal ultrasound technique. Spontaneous preterm birth prophylactic interventions (vaginal cervical cerclage or vaginal progesterone) were offered for short cervical length (≤25 mm) and to women with a history of spontaneous preterm birth or late miscarriage after full-dilatation cesarean delivery. The primary outcome was spontaneous preterm birth; secondary outcomes included short cervical length and a need for prophylactic interventions. A multivariable logistic regression analysis was used to develop multiparameter models that combined cesarean delivery scar parameters, cervical length, history of full-dilatation cesarean delivery, and maternal characteristics. The predictive performance of models was examined using the area under the receiver operating characteristics curve and the detection rate at various fixed false positive rates. The optimal cutoff for cesarean delivery scar distance to best predict a short cervical length and spontaneous preterm birth was analyzed. RESULTS: Cesarean delivery scars were visualized in 90.5% (220/243) of the included women. The spontaneous preterm birth rate was 4.1% (10/243), and 12.8% (31/243) of women developed a short cervical length. A history- (n=4) or ultrasound-indicated (n=19) cervical cerclage was performed in 23 of 243 (9.5%) women; among those, 2 (8.7%) spontaneously delivered prematurely. A multiparameter model based on absolute scar distance from the internal os best predicted spontaneous preterm birth (area under the receiver operating characteristics curve, 0.73; 95% confidence interval, 0.57-0.89; detection rate of 60% for a fixed 25% false positive rate). Models based on the relative anatomic position of the cesarean delivery scar to the internal os and the cesarean delivery scar position with niche parameters (length, depth, and width) best predicted the development of a short cervical length (area under the receiver operating characteristics curve, 0.79 [95% confidence interval, 0.71-0.87]; and 0.81 [95% confidence interval, 0.73-0.89], respectively; detection rate of 73% at a fixed 25% false positive rate). Spontaneous preterm birth was significantly more likely when the cesarean delivery scar was <5.0 mm above or below the internal os (adjusted odds ratio, 6.87; 95% confidence interval, 1.34-58; P =.035). CONCLUSION: In pregnancies following a full-dilatation cesarean delivery, cesarean delivery scar characteristics and distance from the internal os identified women who were at risk for spontaneous preterm birth and developing short cervical length. Overall, the spontaneous preterm birth rate was low, but it was significantly increased among women with a scar located <5.0 mm above or below the internal cervical os. Shortening of cervical length was strongly associated with a low scar position. Our novel findings indicate that a low cesarean delivery scar can compromise the functional integrity of the internal cervical os, leading to cervical shortening and/or spontaneous preterm birth. Assessment of the cesarean delivery scar characteristics and position seem to have use in preterm birth clinical surveillance among women with a previous, full-dilatation cesarean delivery and could better identify women who would benefit from prophylactic interventions.

Predicting Spontaneous Pre-term Birth Risk Is Improved When Quantitative Ultrasound Data Are Included With Historical Clinical Data.

OBJECTIVE: Predicting women at risk for spontaneous pre-term birth (sPTB) has been medically challenging because of the lack of signs and symptoms of pre-term birth until interventions are too late. We hypothesized that prediction of the sPTB risk level is enhanced when using both historical clinical (HC) data and quantitative ultrasound (QUS) data compared with using only HC data. HC data defined herein included birth history prior to that of the current pregnancy as well as, from the current pregnancy, a clinical cervical length assessment and physical examination data. METHODS: The study population included 248 full-term births (FTBs) and 26 sPTBs. QUS scans (Siemens S2000 and MC9-4) were performed by registered diagnostic medical sonographers using a standard cervical length approach. Two cervical QUS scans were conducted at 20 ± 2 and 24 ± 2 wk of gestation. Multiple QUS features were evaluated from calibrated raw radiofrequency backscattered ultrasonic signals. Two statistical models designed to determine sPTB risk were compared: (i) HC data alone and (ii) combined HC and QUS data. Model comparisons included a likelihood ratio test, cross-validated receiver operating characteristic area under the curve, sensitivity and specificity. The study's birth outcomes were only FTBs and sPTBs; medically induced pre-term births were not included. DISCUSSION: Combined HC and QUS data identified women at risk of sPTB with better AUC (0.68, 95% confidence interval [CI]: 0.57-0.78) compared with HC data alone (0.53, 95% CI: 0.40-0.66) and HC data + cervical length at 18-20 wk of gestation (average AUC = 0.51, 95% CI: 0.38-0.64). A likelihood ratio test for significance of QUS features in the classification model was highly statistically significant (p < 0.01). CONCLUSION: Even with only 26 sPTBs among 274 births, value was added in predicting sPTB when QUS data were included with HC data.

Oral supplementation of α-lipoic acid (ALA), magnesium, vitamin B6 and vitamin D stabilizes cervical changes in women presenting risk factors for preterm birth.

OBJECTIVE: Recently, the PTB risk has been related to the objective measurement of cervical length (CL), since a CL of less than 25 mm is an accurate predictor of increased risk of PTB. Primary prevention of preterm labor is based on the early identification of symptoms and on pharmacological treatments with tocolytic drugs for inhibition of uterine contractions that are associated with a shortening of the cervix. Unfortunately, most of these drugs have important side effects. PATIENTS AND METHODS: This study aimed to evaluate whether the administration of a combination of oral α-lipoic acid (ALA), magnesium, vitamin B6 and vitamin D to pregnant women presenting risk factors for PTB could reduce the rate of cervical shortening at 19-22 weeks of gestational age. RESULTS: A total of 122 women attending the first-trimester aneuploidy screening at 11-14 weeks of pregnancy and presenting risk factors for PTB were included in the study. Cervical length significantly decreased in the control group compared with the treatment group (-3.86 ± 1.97 vs. 1.50 ± 1.26; p=0.02). Although the rate of preterm birth did not significantly decrease (9.5% vs. 5.1%), admission for threatened PTB was statistically reduced in the treatment group compared with the control group (3.4% vs. 14.3%). CONCLUSIONS: Oral supplementation of ALA, magnesium, vitamin B6 and vitamin D significantly counteracted cervix shortening in pregnant women presenting risk factors for PTB.

Can myometrial thickness/cervical length ratio predict preterm delivery in singleton pregnancies with threatened preterm labor? A prospective study.

OBJECTIVE: To investigate whether myometrial thickness (MT) to cervical length (CL) ratio could be used in the prediction of preterm birth (PTB) in singleton pregnancies presented with threatened preterm labor (TPL). METHODS: After 48 h of successful tocolysis, MT was measured transabdominally from the fundal, mid-anterior walls and the lower uterine segment (LUS) in 46 pregnancies presented with TPL. MT measurements were divided into CL, individually. The main outcome was PTB before 37 weeks of gestation. RESULTS: The patients were divided into two groups as women delivered ≥ 37 weeks (38.68 ± 1.01 weeks) (n = 25) and those delivered < 37 weeks (34.28 ± 2.53 weeks) (n = 21). The mean ± SD CL in the preterm delivery group was significantly shorter than the term delivery group (23.77 ± 9.23 vs 29.91 ± 7.03 mm, p < 0.05). Fundal, mid-anterior or LUS MT values were similar in both groups. However, in those who delivered preterm, the ratios of fundal MT-to-CL (p = 0.026) and mid-anterior MT-to-CL (p = 0.0085) were significantly different compared to those delivered at term. The optimal cutoff values for CL, fundal MT-to-CL and mid-anterior MT-to-CL ratios in predicting PTB were calculated as 31.1 mm, 0.19 and 0.20, respectively. Fundal MT-to-CL ratio predicted preterm delivery with 71% sensitivity, 72% specificity, 68% positive and 75% negative predictive values. For mid-anterior MT-to-CL ratio, respective values were 76, 76, 73 and 79%. CONCLUSION: Measurement of MT along with CL may offer a promising method in the management of women presented with TPL.

Vaginal fetal fibronectin evaluation before and immediately after ultrasonographic vaginal cervical length measurements in symptomatic women at risk of preterm birth: a pilot study.

OBJECTIVE: To determine if vaginal ultrasound for cervical length measurement induces the release of vaginal fetal fibronectin (fFN), leading to a false-positive fFN test. METHODS: Participants included women with singleton pregnancies at 24-34 weeks' gestation who presented with uterine contractions without bleeding or membrane rupture. Women who had had intercourse or underwent pelvic examination less than 24 h previously were excluded. The first fFN test was followed immediately by vaginal ultrasonography with a transvaginal probe (three images per patient) and, thereafter, a second fFN test. RESULTS: The first fFN test was positive in three patients, and in all, the second, post-ultrasound, fFN test was also positive. In all women with a negative baseline fFN test (n = 25), the second, post-ultrasound, fFN test was also negative. CONCLUSION: Vaginal ultrasound examination does not artificially change the fFN status. This is in contrast to common understanding and may permit the performance of ultrasound examination before fFN, which can be restricted to cases of short cervix.