BACKGROUND AND PURPOSE:

• Generally, obstetric risk assessment is based on factors including
  • Maternal age | BMI | Preexisting comorbidities | Past obstetrical history
  • Parity is generally not considered an independent risk factor for identifying women at increased risk of complications that would lead to escalation to a higher level-of-care facility  
• Jardine at al. (BMJ, 2020), using current UK guidelines, sought to determine if pregnancy risk classification could be improved by stratifying based on parity and the number of risk factors

METHODS:

• Cohort study
• Participants
  • Women with a singleton birth at term following a trial of labor
• Study design
  • Women classified according to the NICE guideline as being at low, intermediate, and increased risk at the time of birth
  • Rate of complications and interventions were calculated
  • Extent to which the risk classification could be improved was then determined based on
    • Number of risk factors between nulliparous women and multiparous women
    • With and without previous caesarean delivery

RESULTS:

• 276,766 women were included
• Multiparous women without a history of cesarean section had the lowest rates of complicated birth
  • Without specific risk factors: 8.8% (95% CI, 8.6 to 9.0%)
  • ≥3 specific risk factors: 21.8% (95% CI, 20.2 to 23.4%)
• Complicated birth rate was higher in nulliparous women
  • Without specific risk factors: 43.4% (95% CI, 43.0 to 43.8%)
  • ≥3 specific risk factors: 64.3% (95% CI, 60.3% to 68.3%)
• Rate of complicated birth was highest in multiparous women with a previous cesarean
  • Without specific risk factors: 42.9% (95% CI, 41.8 to 44.0%)
  • ≥3 specific risk factors: 66.3% (95% CI, 63.0 to 69.5%)

CONCLUSION:

• In women without a previous cesarean, nulliparous women were at greater risk for complications than multiparous women
  • This was true even if the multiparous women had multiple risk factors
• The authors suggest that risk assessment should be grouped by parity and previous mode of birth first, and then risk assessment performed within these groups according to presence of specific risk factors
• In addition, the authors conclude

…nulliparous women, including those without additional risk factors, have considerably higher risks of a complicated birth, and they could consider giving birth in a setting that enables rapid access to care by an obstetric or neonatal team 

Learn More – Primary Sources:

Risk of complicated birth at term in nulliparous and multiparous women using routinely collected maternity data in England: cohort study

Related ObG Topics:

Using Past Placental Complications to Predict Future Risk

ACOG Recommendations: When to Deliver Medically Complicated Pregnancies

Can Evidence-Based Interventions Reduce C-section Complications?

Does a Prior C-Section Increase Risk of Preterm Birth in Later Pregnancies?