Does the presence of a cesarean section scar influence the site of placental implantation and subsequent migration in future pregnancies: a prospective case-control study

Effect of previous caesarean section on reproductive and pregnancy outcomes after assisted reproductive technology: A systematic review and meta‑analysis

Pregnancies following previous caesarean section (CS) are associated with higher incidence of infections, postpartum haemorrhage and obstetric complications. The present study aimed to explore the effect of previous CS on reproductive, maternal and neonatal outcomes in women who underwent assisted reproductive techniques (ART). A systematic review and meta-analysis were conducted to assess reproductive and pregnancy outcomes following ART in women with and without a previous CS. Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines were followed. Eligible language articles written in English, published up to October 2023, were identified in Medline, Google Scholar and Science Direct databases. The quality of the included studies was assessed using the Newcastle Ottawa Scale. A total of 19 articles, reporting on 13 different outcomes met the inclusion criteria. It was revealed that women with previous CS had 9% lower clinical pregnancy rates, 13% lower live birth rates, 11% lower implantation rates and 28% lower multiple pregnancy rates compared with women who had prior natural vaginal deliveries. Additionally, previous CS was associated with an 8-fold higher risk of difficult embryo transfers. No significant differences were noted in ectopic pregnancy rates, miscarriage rates or biochemical pregnancy rates. The present systematic review and meta-analysis demonstrated that previous CS is associated with decreased prospects of clinical pregnancy, live birth and successful embryo implantation during ART. The findings of the present study underscored the need to counsel women with prior CS regarding its potential impact on ART outcomes.

Previous mode of delivery and pregnancy outcomes after single euploid embryo transfer: A retrospective study

RESEARCH QUESTION

Are the pregnancy outcomes (clinical, biochemical and ectopic pregnancies) of women with a history of vaginal birth and women with a history of caesarean section who underwent single euploid embryo transfer at Fakih IVF Fertility Centre comparable?

DESIGN

This retrospective cross-sectional chart review with multi-variate analysis, including 1157 women, compared pregnancy outcomes between women with a history of caesarean section and women with a history of vaginal birth who underwent in-vitro fertilization (IVF) at Fakih IVF Fertility Centre. All women who underwent single euploid frozen embryo transfer were included. Fresh and multiple embryo transfers were excluded. The primary outcome was clinical pregnancy, and the secondary outcomes were biochemical and ectopic pregnancies.

RESULTS

Regarding pregnancy outcomes, the caesarean section group had fewer clinical pregnancies than the vaginal birth group [299 (61.1 %) vs 417 (67.3 %); p = 0.0346]. The rate of ectopic pregnancy did not differ significantly between the two groups (p = 0.4320). Similarly, there was no significant difference between the two groups regarding biochemical pregnancy [caesarean section group 22 (4.3 %) vs vaginal birth group 26 (4.0 %); p = 0.8122].

CONCLUSION

This study showed a decreased likelihood of clinical pregnancy in women with a history of caesarean section. No significant differences in biochemical or ectopic pregnancies were observed between the groups. These findings have practical clinical implications for counselling patients on the impact of prior caesarean sections in assisted reproduction.

Caesarean Section Scar and Placental Location at the First Trimester of Pregnancy-A Prospective Longitudinal Study

Background and Objectives: This study aims to report the location of the placenta in the first trimester of pregnancy in groups of women according to the number of previous caesarean deliveries and the visibility of the caesarean scar niche. Materials and Methods: The prospective observational research included adult women aged 18 to 41 years during pregnancy after one or more previous caesarean sections (CSs). Transvaginal (TVS) and transabdominal sonography (TAS) was used to examine the uterine scar and placental location during 11-14 weeks. The CS scar niche ("defect") was bordered in the sagittal plane as a notch at the previous CS scar's site with a depth of 2.0 mm or more. A comparative analysis of the placental location (high or low and anterior or posterior) was performed between groups of women according to the CS number and the CS scar niche. Results: A total of 122 participants were enrolled during the first-trimester screening. The CS scar defect ("niche") was visible in 40.2% of cases. In cases after one previous CS, the placenta was low in the uterine cavity (anterior or posterior) at 77.4%, and after two or more CSs, it was at 67.9%. Comparing the two groups according to the CS scar niche, the placenta was low in 75.5% of cases in the participant group with a CS scar niche and in 75% of cases without a CS scar niche (p = 0.949). Conclusions: The number of previous caesarean deliveries has no effect on the incidence rate of low-lying placentas in the first trimester. Moreover, the presence of the CS scar niche is not associated with anterior low-lying placentas.

Impact of Caesarean section on pregnancy outcomes in ART after transfer of one or more frozen blastocysts

INTRODUCTION

The prevalence of Caesarean delivery is rising steadily worldwide, and it is important to identify its future impact on fertility. A number of articles have been published on this subject, but the impact of Caesarean section on reproductive outcomes is still under debate, and none of these articles focus exclusively on frozen blastocysts.

OBJECTIVE

The aim of this study was to evaluate the impact of a previous Caesarean delivery compared with a previous vaginal delivery on the chances of a live birth following the transfer of one or more frozen embryos at the blastocyst stage.

METHODS

This was a retrospective, bicentric study at the University Hospitals of Nîmes and Montpellier, conducted between January 1st, 2016 and February 1st, 2021. Three hundred and ninety women with a history of childbirth and a transfer of one or more frozen embryos at blastocyst stage were included in the analysis. The primary outcome was the number of live births. Secondary outcomes were: the rate of positive HCG, miscarriage, ectopic pregnancy and clinical pregnancy, as well as the live birth rate according to the presence or absence of an isthmocele.

RESULTS

Of the 390 patients included, 118 had a previous Caesarean delivery and 272 a vaginal delivery. No statistically significant differences were found for the primary (p = 0.9) or secondary outcomes. A trend towards lower live birth rates was observed in patients with isthmoceles, but this did not reach significance (p>0.9). On the other hand, transfers were more often described as difficult in the Caesarean delivery group (p = 0.011).

CONCLUSION

Our study found no effect of previous Caesarean delivery on the chances of live birth after transferring one or more frozen blastocysts. However, further prospective studies are needed to confirm these results.

A nomogram to predict the risk of scar pregnancy after caesarean section

The aim of this study was to identify the high-risk factors for caesarean scar pregnancy (CSP) and establish a nomogram to predict the risk of caesarean scar pregnancy in pregnant women with a history of caesarean section. Among 1273 pregnant women with a history of caesarean section, 70% of the patients (892 patients, training sample) were randomly selected for analysis, and a prediction model was generated. The remaining patients (381 patients, validation sample) were validated for the model. Four high-risk factors for CSP were established, including: parity, number of previous abortions, uterus position, and early vaginal bleeding. The area under the curve of the nomogram for the training set was 0.867 and that for the validation set was 0.881, indicating good performance. Calibration curves for predicting CSP showed good calibrations. Decision curve analyses showed good application prospects for the model. Our results show that our nomogram for predicting CSP risks can be a practical tool to help in the early identification of CSP.Impact StatementWhat is already known on this subject? The high-risk factors for "caesarean scar pregnancy", An simple nomogram could be constructed to predict the risk of the disease through these high-risk factors.What do the results of this study add? This study can quickly predict whether the patient is a high-risk group for uterine scar pregnancy based on the patient's previous pregnancy, early vaginal bleeding and uterine position.What are the implications of these findings for clinical practice and/or further research? Caesarean scar pregnancy was secondary Long-term complications after caesarean section that with a high risk of pregnancy. In this study, we established a nomogram based on the number of cases of CSP and a control group with a history of caesarean section delivery at term, The high-risk factors were assigned a certain risk value in the early stage, if the woman contains more high-risk factors, the higher the risk of developing CSP, it should be highly valued in the early stage, and the rate of visiting a doctor should be increased.

Placental location and obstetrical-neonatal outcomes: A retrospective study

OBJECTIVE

To explore the potential association of lateral placentation with pregnancy outcome.

METHODS

The database of a tertiary medical center was searched for women who gave birth to a singleton neonate from 2012 to 2020 for whom placental location was documented during antepartum sonographic examination. Clinical data were compared between patients with a central (anterior/posterior/fundal) or lateral placenta using standard statistics. The primary outcome measure was neonatal birthweight, and secondary outcome measures were pregnancy complications and mode of delivery.

RESULTS

The cohort included 12 306 women: 11 608 (94%) with a central placenta and 698 (5.6%) with a lateral placenta. The lateral placenta group had higher rates (P < 0.05) of prior and current cesarean delivery, assisted delivery, and preterm birth. On multivariate regression analyses, placental location (adjusted odds ratio [aOR], 1.36; 95% confidence interval [CI], 1.11-1.66) and maternal age (aOR, 1.02; 95% CI, 1.01-1.03) were associated with risk of preterm birth. Lateral placenta (aOR, 1.22; 95% CI, 1.02-1.47), maternal age (aOR, 1.07; 95% CI, 1.06-1.08), parity (aOR, 0.32; 95% CI, 0.28-0.35), and prior cesarean delivery (aOR, 12.00; 95% CI, 10.60-13.60) were associated with risk of current cesarean delivery.

CONCLUSION

The findings suggest that lateral placentation may pose a risk of preterm birth and cesarean delivery compared with central placentation.

Impact of previous Caesarean section on reproductive outcomes after assisted reproductive technology: systematic review and meta-analyses

This meta-analysis investigated whether a previous Caesarean section has an impact on the outcomes of treatment with assisted reproductive technology (ART). PubMed, Embase, Cochrane Library, Web of Science and Google Scholar were searched. Clinical trials published in English up to May 2020 were included. Seven studies performed between 2016 and 2020 met all the inclusion criteria. It was found that previous Caesarean section leads to significantly decreased clinical pregnancy rate (CPR) (risk ratio [RR] 0.86; 95% confidence interval [CI], 0.81, 0.92; P < 0.00001) and live birth rate (LBR) (RR 0.80; 95% CI 0.73, 0.86; P < 0.00001). Caesarean section increased the miscarriage rate (RR 1.39; 95% CI 1.18, 1.64; P < 0.0001), and difficult transfer (RR 8.23; 95% CI 4.63, 14.65; P < 0.00001) after ART compared with women who had previous vaginal delivery. The combined results also showed similar endometrial thickness, number of oocytes retrieved, implantation rate, ectopic pregnancy rate, preterm birth and stillbirth between women with previous Caesarean section and women with previous vaginal delivery. In conclusion, Caesarean sections have a detrimental effect on CPR and LBR, and increase the risk of miscarriage and difficult transfer. The indications for Caesarean section should be strictly controlled, and full consultation should be provided to pregnant women. Further studies with stratification analysis of twin and single pregnancies are needed to evaluate the impact of Caesarean section.

Uterine Scarring Leads to Adverse Pregnant Consequences by Impairing the Endometrium Response to Steroids

Uterine surgical scarring is an increasing risk factor for adverse pregnant consequences that threaten fetal-maternal health. The detailed molecular features of scar implantation remain largely unknown. We aim to study the pathologic features of uterine surgical scarring and the mechanisms of compromised pregnancy outcomes of scar implantation. We generated a mouse model of uterine surgical scarring with a uterine incision penetrating the myometrium to endometrium to examine the pathologic changes and transcriptome profiles of uterine scarring at various postsurgery (PS) time points, as well as features of the feto-maternal interface during scar implantation. We found that uterine surgical scar recovery was consistently poor at PS3 until PS90, as shown by a reduced number of endometrial glands, inhibition of myometrial smooth muscle cell growth but excessive collagen fiber deposition, and massive leukocyte infiltration. Transcriptome annotation indicated significant chronic inflammation at the scarring site. At the peri-implantation and postimplantation stages, abnormal expression of various steroid-responsive genes at the scarring site was in parallel with lumen epithelial cell hyperplasia, inappropriate luminal closure, and disorientation of the implanted embryo, restricted stromal cell proliferation, and defective decidualization. High embryonic lethality (around 70%) before E10.5 was observed, and the small amount of survival embryos at E10.5 exhibited restricted growth and aberrant placenta defects including overinvasion of trophoblast cells into the decidua and insufficient fetal blood vessel branching in the labyrinth. The findings indicate that chronic inflammation and compromised responses to steroids in uterine scar tissues are the pivotal molecular basis for adverse pregnancy consequences of scar implantation.

[Placental Locations in Subsequent Pregnancies - A Retrospective Study]

INTRODUCTION

Different locations of the placenta are associated with specific risks during pregnancy and labor. Knowledge of the placental location helps to provide better care for the expectant mother and her unborn child. Whereas multiple studies show a higher risk for a recurrent placenta previa, hardly any such data is available for any other placental location. The aim of this study was to analyze the frequency of distribution of different placental locations and to evaluate correlations between placental locations in subsequent pregnancies.

MATERIAL AND METHODS

In a retrospective cohort study women with singleton pregnancies ≥ 24 gestational weeks who had at least one ultrasound with identification of the placental location and gave birth to their firstborn and at least one more following child at our hospital between 2007 and 2016 were evaluated. Exclusion criteria were multiple pregnancies, abortions, intrauterine fetal death, and fetal malformations. Placental locations were classified into anterior, posterior, fundal, right, left, and previa.

RESULTS

Data of 1657 women were analyzed. The most frequent location was anterior, followed by posterior, fundal and lateral, and previa. Statistical analysis showed no significant correlations in subsequent pregnancies regarding placental locations.

CONCLUSION

Placental locations in subsequent pregnancies seem not to be influenced by previous pregnancies. Therefore no prognosis for placental location can be made concerning future pregnancies.

Effect of a prior cesarean delivery on pregnancy outcomes of frozen-thawed embryo transfer: A retrospective cohort study in a freeze-all setting

INTRODUCTION

The association between the mode of previous delivery and subsequent success of assisted reproductive treatment has been poorly understood. By mitigating the detrimental effect of supraphysiologic estradiol levels on endometrial receptivity, a freeze-all strategy provides a novel model to investigate the sole impact of a prior cesarean delivery (CD) on embryo transfer outcomes.

MATERIAL AND METHODS

This single-center retrospective cohort study included 2660 patients who underwent their first frozen-thawed embryo transfer cycles after a freeze-all policy from January 2013 to December 2018. Patients with a history of live birth by CD were assigned to the CD group, and those with only vaginal delivery (VD) were categorized into the VD group. The primary outcome measure was live birth. Baseline characteristics of the two groups were balanced by propensity score matching in a ratio of 1:1. Univariate and multivariate logistic regression analyses were performed using the after-matching data.

RESULTS

Compared with the VD group, the rates of clinical pregnancy (38.3% vs 44.5%; P = .005) and live birth (27.5% vs 33.4%; P = .003) were significantly lower in women with a history of CD. When adjusted for a number of major confounding factors, the negative association between a prior CD and frozen-thawed embryo transfer success was maintained, with the adjusted odds ratio (OR) being 0.80 (95% CI 0.66-0.96) and 0.78 (95% CI 0.63-0.95) for clinical pregnancy and live birth, respectively. Furthermore, a CD history conferred a marginally increased risk of early miscarriage (crude OR 1.48, 95% CI 1.04-2.11; adjusted OR 1.47, 95% CI 1.01-2.14), whereas the odds of multiple and ectopic pregnancy did not show significant differences before and after adjustment.

CONCLUSIONS

A prior CD was associated with a decreased chance of live birth and an increased risk of early miscarriage in frozen-thawed embryo transfer cycles.

Does previous cesarean section influence neonatal birth weight? A path analysis in China

BACKGROUND

Since the One-child Policy was revised to a Two-child policy in 2013, the number of pregnancies with previous cesarean section suddenly increased in China. The aim of this study was to test if a previous cesarean section influenced the neonatal birth weight under Chinese background.

METHODS

A retrospective study was conducted. Path analysis was used to test the hypothesized model for the association among previous cesarean section, placenta previa, gestational age and neonatal birth weight. Comparative fit index, the root-mean-square error of approximation and weighted root-mean-square residual were used to evaluate the model fit.

RESULTS

3466 electronic records for second pregnancies met the criteria; a modified model was established (the root-mean-square error of approximation=0.049, comparative fit index=0.992, weighted root-mean-square residual=0.960). The effects of previous cesarean section on neonatal birth weight were mediated via four paths. The direct effects (coefficient: 0.056) showed opposite signs compared to indirect effects (coefficient: -0.127) in this path analysis. It meant that the negative effects of the previous cesarean section were suppressed by other factors which bring positive effects.

CONCLUSION

This study showed that previous cesarean section had negative effects on neonatal birth weight with increasing incidence of placenta previa and preterm birth. But these effects were suppressed by other positive factors, such as maternal body mass index, just after the child policy updated in China.

Reproductive outcomes in women with prior cesarean section undergoing in vitro fertilization: A retrospective case-control study

The impact of prior cesarean section (CS) on the pregnancy and neonatal outcomes of in vitro fertilization and embryo transfer (IVF-ET) was investigated. A retrospective analysis was performed on 144 patients with prior CS between January 2013 and December 2015. The pregnancy, delivery, and neonatal outcomes of patients who had previous CS delivery and received IVF-ET were analyzed. The control group comprised 166 patients who had only previous vaginal delivery (VD) and received IVF-ET during the same period. The results showed that the basal follicle stimulating hormone level, estradiol level on human chorionic gonadotropin (hCG) day, gonadotrophin dosage, duration of stimulation, retrieved oocytes, fertilization rate, high-quality embryo rate, multiple birth rate, abortion rate and ectopic pregnancy rate had no significant difference between the two groups (P>0.05). The pregnancy rate (40.28% vs. 54.22%) and implantation rate (24.01% vs. 34.67%) were significantly lower (P<0.05), and the ratio of embryo difficulty transfer (9/144 vs. 0/166) was significantly higher in CS group than in VD group. The risk of pernicious placenta previa and postpartum hemorrhage in twin deliveries was significantly increased in CS group as compared with that in VD group (P<0.05), and gestational age and neonatal birth weight were significantly reduced in twin deliveries as compared with singleton deliveries in both groups (P<0.05). It was suggested that the existence of CS scar may impact embryo implantation and clinical pregnancy outcome, and increase the difficulty of ET. We should limit the number of transfer embryos to avoid multiple pregnancies and strengthen gestational supervision in patients with cesarean scar.

Placental location, postpartum hemorrhage and retained placenta in women with a previous cesarean section delivery: a prospective cohort study

OBJECTIVE

Women previously giving birth with cesarean section have an increased risk of postpartum hemorrhage (PPH) and retained placenta. The objective of this study was to determine if anterior placental location increased the risk of PPH and retained placenta in such women.

MATERIALS AND METHODS

We performed a prospective cohort study on 400 women with cesarean section delivery in a previous pregnancy. Ultrasound examinations were performed at gestational week 28-30, and placental location, myometrial thickness, and three-dimensional vascularization index (VI) were recorded. Data on maternal age, parity, BMI, smoking, gestational week at delivery, induction, delivery mode, oxytocin, preeclampsia, PPH, retained placenta, and birth weight were obtained for all women. Outcome measures were PPH (≥1,000 mL) and retained placenta.

RESULTS

The overall incidence of PPH was 11.0% and of retained placenta 3.5%. Twenty-three women (11.8%) with anterior placenta had PPH compared to 12 (6.9%) with posterior or fundal locations. The odds ratio was 1.94, but it did not reach statistical significance. There was no significant risk increase for retained placenta in women with anterior placentae. Seven of eight women with placenta previa had PPH, and four had retained placenta.

CONCLUSIONS

The overall risk of PPH and retained placenta was high for women with previous cesarean section. Anterior location of the placenta in such women tended to impose an increased risk for PPH but no risk increase of retained placenta. Placenta previa in women with previous cesarean section is associated with a high risk for PPH and retained placenta.

Relationship between placenta location and resolution of second trimester placenta previa

This prospective study was conducted to assess the rate of resolution of second trimester placenta previa in women with anterior placenta and posterior placenta, and that in women with and without previous cesarean section. In this study, placenta previa was defined as a placenta lying within 20 mm of the internal cervical os or overlapping it. We recruited 183 women diagnosed with previa between 20⁺⁰ weeks and 25⁺⁶ weeks. They were grouped according to their placenta location (anterior or posterior) and history of cesarean section. Comparative analysis was performed on demographic data, resolution rate of previa and pregnancy outcomes between anterior group and posterior group, and on those between cesarean section group and non-cesarean section group. Women with an anterior placenta tended to be advanced in parity (P=0.040) and have increased number of dilatation and curettage (P=0.044). The women in cesarean section group were significantly older (P=0.000) and had more parity (P=0.000), gravidity (P=0.000), and dilatation and curettage (P=0.048) than in non-cesarean section group. Resolution of previa at delivery occurred in 87.43% women in this study. Women with a posterior placenta had a higher rate of resolution (P=0.030), while history of cesarean section made no difference. Gestational age at resolution was earlier in posterior group (P=0.002) and non-cesarean section group (P=0.008) than in anterior group and cesarean section group correspondingly. Placenta location and prior cesarean section did not influence obstetric outcomes and neonatal outcomes. This study indicates that it is more likely to have subsequent resolution of the previa when the placenta is posteriorly located for women who are diagnosed with placenta previa in the second trimester.

The clinical outcome of cesarean scar pregnancies implanted "on the scar" versus "in the niche"

BACKGROUND

The term cesarean scar pregnancy refers to placental implantation within the scar of a previous cesarean delivery. The rising numbers of cesarean deliveries in the last decades have led to an increased incidence of cesarean scar pregnancy. Complications of cesarean scar pregnancy include morbidly adherent placenta, uterine rupture, severe hemorrhage, and preterm labor. It is suspected that cesarean scar pregnancies that are implanted within a dehiscent scar ("niche") behave differently compared with those implanted on top of a well-healed scar. To date there are no studies that have compared pregnancy outcomes between cesarean scar pregnancies implanted either "on the scar" or "in the niche."

OBJECTIVES

The purpose of this study was to determine the pregnancy outcome of cesarean scar pregnancy implanted either "on the scar" or "in the niche."

STUDY DESIGN

This was a retrospective 2-center study of 17 patients with cesarean scar pregnancy that was diagnosed from 5-9 weeks gestation (median, 8 weeks). All cesarean scar pregnancies were categorized as either implanted or "on the scar" (group A) or "in the niche" (group B), based on their first-trimester transvaginal ultrasound examination. Clinical outcomes based on gestational age at delivery, mode of delivery, blood loss at delivery, neonate weight and placental histopathologic condition were compared between the groups with the use of the Mann-Whitney U test. Myometrial thickness overlying the placenta was compared among all the patients who required hysterectomy and those who did not with the use of the Mann-Whitney U test. Myometrial thickness was also correlated with gestational age at delivery with the use of Spearman's correlation.

RESULTS

Group A consisted of 6 patients; group B consisted of 11 patients. Gestational age at delivery was lower in group B (median, 34 weeks; range, 20-36 weeks) than in group A (median, 38 weeks; range, 37-39 weeks; P=.001). In group A, 5 patients were delivered via cesarean delivery (with normal placenta), and 1 patient underwent a cesarean-hysterectomy for placenta accreta. In group B, 10 patients had a cesarean-hysterectomy for placenta increta/percreta, and 1 patient underwent gravid-hysterectomy for vaginal bleeding at 20 weeks gestation. Blood loss was increased, but not significantly higher in group B (median, 1200 mL; range, 600-4000 mL) than in group A (median, 700 mL; range, 600-1400 mL; P=.117). Myometrium was statistically significantly thinner in the patients group that require hysterectomy (median, 1 mm; range, 0-2 mm) than in the group that did not (median, 5 mm; range, 4-9 mm; P=.001). Myometrial thickness showed a positive correlation with the gestational age (r=0.820; P<.0005).

CONCLUSION

Patients with cesarean scar pregnancy implanted "on the scar" had a substantially better outcome compared with patients in whom the cesarean scar pregnancy implanted "in the niche." Myometrial thickness <2 mm in the first-trimester ultrasound examination is associated with morbidly adherent placenta at delivery.

Placental implantation and migration following a previous caesarean section scar

This prospective cohort study was conducted in Arash Women's Hospital between August 2014 and August 2015 to define the relationship between caesarean section scar and placental implantation and migration. Seven hundred and thirty women with one previous birth (caesarean section or vaginal delivery) and a singleton pregnancy underwent three ultrasound examinations for placental evaluation at 11-14, 20 and 34 weeks gestation. Previous caesarean section was related to the increased odds of anterior placental implantation but no relation was seen between low-lying placenta or placenta praevia and previous caesarean. The placental migration from low-lying to non-low-lying position was similar between women with and without previous caesarean.

Does the presence of a Caesarean section scar affect implantation site and early pregnancy outcome in women attending an early pregnancy assessment unit?

STUDY QUESTION

Are there any differences in the location and distance to the internal cervical ostium of the implantation site of the intrauterine gestation sacs, early pregnancy symptoms and pregnancy outcome at 12 weeks gestation between women with and without a previous Caesarean section (CS)?

SUMMARY ANSWER

The presence of a CS scar affects the site of implantation, and the distance between implantation site and the scar is related to the risk of spontaneous abortion. WHAT IS KNOWN ALREADY?: Little is known about the impact of a CS scar on implantation other than the risk of Caesarean scar pregnancy (CSP). Furthermore, there is a paucity of information on how the proximity of implantation to the scar impacts on pregnancy outcome in the first trimester.

STUDY DESIGN, SIZE, AND DURATION

A prospective cohort study conducted over 15 months in the early pregnancy unit of a London Teaching Hospital. Three hundred and eighty women underwent a transvaginal scan at 6-11 weeks of gestation. A total of 170 women had undergone ≥1 CS, and 210 women had no history of CS.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The 380 women were recruited as consecutive non-selected cases. The relationship between the implanted sac and the CS scar was assessed by quantifiable measures and by subjective impression. Logistic regression analysis was used to determine the influence of the presence of a CS scar on pregnancy outcome. The final outcome of the study was the viability of the pregnancy at 12 weeks.

MAIN RESULTS AND THE ROLE OF CHANCE

Implantation was most frequently posterior (53%) in the CS group and fundal in the non-CS group (42%). Gestation sac implantation was 8.7 mm lower in the CS group (95% confidence interval (CI) 6.7-10.7, P < 0.0001). Presenting complaints differed in women with and without a previous CS (P = 0.0009). More frequent vaginal bleeding [73 versus 55%, difference -18, 95% CI (-27 to -8%] yet no clearly increased spontaneous abortion rates were noted in the CS group compared with the non-CS group (adjusted odds ratio = 1.1, 95% CI 0.6-1.9, P = 0.74). Subjective impression showed that in eight cases the implantation site crossed the scar, seven of which resulted in spontaneous abortion, while the remaining case survived to term complicated by placenta praevia and post-partum haemorrhage. The subjective impression of the examiner was supported by the measurements of distance between implantation site and CS scar.

LIMITATIONS, REASONS FOR CAUTION

A weakness of the study is the lack of a reference technique to verify the location of implantation.

WIDER IMPLICATIONS OF THE FINDINGS

This study adds further support to the hypothesis that the presence of a CS on the uterus impacts on the implantation site of a future pregnancy. The possibility that the CS scar has an impact on the risk of spontaneous abortion should be further studied. Caution must be exercised when implantation occurs near to, and crosses, a CS scar as this is not always associated with the diagnosis of CSP. A potential limitation of the study is that we did not examine scar dimensions and morphology.