Cesarean deliveries during labor linked to risks in future pregnancies

Researchers suggest an association between cesarean sections during labor and recurrent preterm birth or mid-trimester loss in subsequent pregnancies, potentially due to cervical damage

In a recent perspective published in PLOS Medicine, researchers discussed the implications of cesarean section (C-section) deliveries during labor for preterm births in subsequent pregnancies.

Rising rates of C-sections

C-section rates have risen steadily worldwide over the past decades. From 1990 to 2014, the global C-section rate rose by 12.4%. In England, the prevalence is even higher, with over one-third of women delivering by C-section.

Of these, approximately 24% are emergency procedures, and 5% take place when the cervix is fully dilated. In North America, full dilatation C-section rates have surged by 44% over the last decade.

Several factors contribute to this trend, including shifts in clinical and professional training practices, fears related to litigation, and evolving cultural and social expectations. While C-sections can be life-saving during pregnancy complications, their rising use, particularly in emergency settings, raises concerns about their long-term implications for maternal and fetal health.

Future implications for pregnancies

Emergency procedures, especially those late in labor, have been linked to adverse outcomes in future pregnancies. Observational studies suggest a strong association between in-labor C-sections and increased risks of spontaneous preterm birth (sPTB) and mid-trimester pregnancy loss.

The risks are especially pronounced if cervix dilation is greater at the time of surgery, peaking when full dilation has taken place. For the majority of women who undergo an in-labor C-section, preterm birth risk in a future pregnancy remains low (less than 5%). However, women who experience preterm birth after an in-labor C-section are likelier to face recurrent preterm births in subsequent pregnancies.

In a recent analysis, researchers found that women who had an in-labor C-section and later experienced a preterm birth had a 2.7-fold higher risk of recurring sPTB than women with other preterm birth risk factors. When considering mid-trimester losses, the relative risk increased to 5.65. In this cohort, 54% of women who experienced preterm birth following an in-labor C-section went on to have a subsequent preterm delivery, a rate significantly higher than for other high-risk groups.

Cervical damage is a key factor

The observed association between in-labor C-sections, sPTB, and mid-trimester loss may be explained by cervical damage during surgery. The cervix plays a central role in preventing premature labor. Surgical interventions during advanced labor stages often involve incisions close to or within cervical tissue, increasing the likelihood of trauma.

As labor progresses, the head of the fetus descends into the pelvis, making surgical delivery more challenging. This can result in a greater risk of cervical injury due to surgical extensions, sutures, or infection, compromising cervical integrity.

Advanced imaging techniques, such as transvaginal ultrasound (TVUS), provide further insights into the role of cervical damage. Cesarean scars are often visible as disruptions in the uterine wall.

Conventional interventions and alternative approaches

Standard interventions for preventing sPTB, such as transvaginal cerclage (TVC), are less effective among women with prior in-labor C-sections. In TVC, a suture is placed in the cervix during early pregnancy to reduce the risk of preterm labor. However, in women with previous in-labor C-sections, TVC failure rates are high.

A study found that these women were 10 times likelier to deliver before 30 weeks gestation than women with other risk factors. In the same analysis, 46% of the women with prior in-labor C-sections and TVC experienced either sPTB or mid-trimester loss.

For women with cervical damage from in-labor C-sections, transabdominal cerclage (TAC) may be an effective alternative. TAC bypasses damaged cervical tissue, offering better protection than TVC.

A retrospective cohort study found that TAC significantly reduced sPTB rates before 30 weeks compared to TVC (odds ratio 0.09). This suggests that TAC could be a valuable option for women with a history of in-labor C-sections, particularly those with recurrent preterm births.

Conclusion

C-sections are the most common surgical procedure worldwide, impacting nearly one-quarter of women. The potential for cervical damage during in-labor C-sections and its implications for future pregnancies underscores the need for tailored management strategies. Clinicians and patients must recognize these risks and work together in shared decision-making to ensure better maternal and fetal outcomes.

The link between in-labor C-sections, mid-trimester losses, and sPTB highlights an emerging clinical problem. With the increasing prevalence of in-labor C-sections, there is an urgent need to address this issue through improved training in instrumental delivery and labor management. Further investigation is also needed to understand better the mechanisms driving cervical damage and to develop strategies for minimizing harm.

Improved imaging protocols could play a crucial role in identifying at-risk women and guiding treatment decisions. Additionally, evaluating the effectiveness of interventions, such as TAC, in preventing adverse outcomes could inform future clinical guidelines.