Women who undergo a caesarean section at full cervical dilatation face a significantly higher risk of spontaneous preterm birth and second-trimester pregnancy loss in future pregnancies, according to a 2026 study published in Reproductive Health. Researchers found that for every additional centimetre of cervical dilatation during a first-term caesarean, the risk of subsequent preterm birth increases by 27%, with those experiencing uterine extensions facing up to an 8.2-fold higher risk.
Why does full-dilatation caesarean section increase future risk?
A caesarean section at full cervical dilatation (CSFD) carries higher physical risks than elective procedures because the fetal head is deeply engaged in the pelvis. According to the study by Minisha F et al., this position often requires more complex surgical maneuvers to extract the infant. These maneuvers can cause “uterine extensions”—tears or incisions that extend beyond the intended uterine opening. These extensions, particularly those measuring 3–5 cm, appear to weaken the structural integrity of the lower uterine segment, which is critical for supporting subsequent pregnancies.
The study found that while the rate of spontaneous preterm birth for elective caesarean patients was 3–6%, the rate for those who underwent CSFD climbed to nearly 18%.
What are the long-term implications for pregnancy planning?
The data suggests that obstetric history must now include specific details about the stage of labour during a previous caesarean. Authors of the Reproductive Health study argue that women with a history of CSFD, especially those who experienced uterine extensions, should be flagged for high-risk monitoring. Clinical pathways for these patients may soon include:
- Serial cervical length monitoring: Using ultrasound to track the shortening of the cervix throughout the second trimester.
- Vaginal progesterone therapy: A standard intervention used to help prevent preterm labour in high-risk patients.
- Cervical cerclage: A surgical procedure where the cervix is stitched closed to prevent premature opening.
How do surgical complications compare across different delivery types?
The risk profile varies significantly depending on the timing of the procedure. Research indicates that the risks for women who undergo CSFD are markedly higher than those who have elective procedures or even those who undergo surgery during the latent phase of labour.
| Delivery Type | Preterm Birth Risk |
|---|---|
| Elective Caesarean | 3–6% |
| CSFD (Full Dilatation) | ~18% |
| CSFD with Uterine Extensions | Up to 8.2x higher risk |
Frequently Asked Questions
Does every caesarean section increase the risk of preterm birth?
No. The study highlights that the risk is specifically elevated for caesarean sections performed at full cervical dilatation. Elective caesareans do not carry the same statistical risk for future preterm birth.
What are uterine extensions?
Uterine extensions are unintended tears that occur in the uterine wall during the delivery of the baby’s head. They are more common when the head is deeply engaged in the birth canal during an emergency or late-labour caesarean.
Can I have a healthy pregnancy after a CSFD?
Yes. While the statistical risk is higher, many women go on to have healthy, full-term pregnancies. The primary recommendation from researchers is to discuss your surgical history with an obstetrician early in your next pregnancy to determine if extra monitoring is necessary.
If you have had a previous caesarean, request your operative report from the hospital. Sharing this document with your current care provider allows them to see if uterine extensions were noted, which helps them tailor your prenatal care plan.
Have you had a conversation with your doctor about your birth history? Share your experiences in the comments below or subscribe to our newsletter for the latest updates on maternal health research.
Reference: Minisha F et al. “Risk of preterm birth and second-trimester loss following intrapartum cesarean sections and uterine extensions: a population-based cohort study.” Reproductive Health, 2026. DOI: 10.1186/s12978-026-02387-w
