BACKGROUND AND PURPOSE:

• Schummers et al. ( JAMA Internal Medicine, 2018) sought to determine whether maternal age modifies the association between short interpregnancy (delivery to conception) interval and adverse pregnancy outcomes

METHODS:

• Population-based cohort study
  • ≥2 singleton pregnancies
• Risks of each outcome for 3- to 24-month interpregnancy intervals were estimated, according to maternal age at index birth
  • 20-34
  • ≥35 years
• Main outcomes
  • Maternal mortality or severe morbidity: Mechanical ventilation, blood transfusion >3 U, intensive care unit admission, organ failure, death)
  • SGA: <10^th percentile BW for gestational age and sex
  • Fetal and infant composite outcome: Stillbirth, infant death, <3rd BW percentile for gestational age and sex, delivery <28 weeks
  • Spontaneous and indicated preterm delivery

RESULTS:

• • 148,544 pregnancies subsequent to a live birth
  • Risk curves were U- or L-shaped
    • Nadirs for the various outcomes were approximately 18 months
    • Low risks were seen for most outcomes between 12- to 24-month intervals
  • Increased 6-month vs 18-month interpregnancy intervals for women aged 35 years or older
    • 0.62% at 6 months vs 0.26% at 18 months
    • Adjusted risk ratio (RR) 2.39 (95% CI, 2.03-2.80)

• No increase in 6-month vs 18-month interpregnancy intervals for women aged 20 to 34 years
  • 0.23% at 6 months vs 0.25% at 18 months
  • aRR 0.92 (95% CI, 0.83-1.02)
• Risk ratio for adverse fetal and infant outcomes comparing 6 vs 18 months were greater for women aged 20 to 34 years than women ≥35 years
  • 20 to 34 years: 2.0% at 6 months vs 1.4% at 18 months (aRR 1.42; 95% CI, 1.36-1.47)
  • ≥35 years: 2.1% at 6 months vs 1.8% at 18 months (aRR 1.15; 95% CI, 1.01-1.31)
• Risk ratio for spontaneous preterm delivery comparing 6 months to 18 months was greater for women 20 to 34 years
  • 20 to 34 years: 5.3% at 6 months vs 3.2% at 18 months (aRR 1.65; 95% CI, 1.62-1.68)
  • ≥35 years: 5.0% at 6 months vs 3.6% at 18 months (aRR 1.40; 95% CI, 1.31-1.49)

CONCLUSION:

• Short interpregnancy intervals that are less than <12 months are associated with increased risk for adverse pregnancy outcomes for all women across all ages
• These risks persist after stratifying based on maternal age
• The authors also state

Our findings indicate a shorter optimal interval than previously thought (12-24 months) for women of all ages. This finding may be reassuring particularly for older women who must weigh the competing risks of increasing maternal age with longer interpregnancy intervals

Learn More – Primary Sources:

Association of Short Interpregnancy Interval With Pregnancy Outcomes According to Maternal Age

Related ObG Topics:

Interpregnancy Interval and Adverse Perinatal Outcomes 

Benefit or Risk to Delaying Pregnancy after Miscarriage?

Maternal Age: What is the Impact on Stillbirth and Other Adverse Pregnancy Outcomes?