Unintended pregnancy and interpregnancy interval by maternal age, National Survey of Family Growth.

Background: The relationship between unintended pregnancy and interpregnancy interval (IPI) across maternal age is not clear.

Methods: Using data from the National Survey of Family Growth, we estimated the percentages of pregnancies that were unintended among IPI groups (<6, 6-11, 12-17, 18-23, 24+ months) by maternal age at last live birth (15-19, 20-24, 25-29, 30-44 years).

Results: Approximately 40% of pregnancies were unintended and 36% followed an IPI<18 months. Within each maternal age group, the percentage of pregnancies that were unintended decreased as IPI increased.

Conclusion: Unintended pregnancies are associated with shorter IPI across the reproductive age spectrum.