Short interval between pregnancies

A short gap between one pregnancy and the next. A 2006 review of studies found higher odds of preterm birth, low birth weight and a smaller baby than expected for the time in pregnancy when the gap was short. These are links seen in observational studies, not proof that the gap itself is the cause.

Risk factor
In this atlas

Overview

Technical summary

In a 2006 JAMA meta-analysis of 67 articles, compared with an interpregnancy interval of 18 to 23 months, intervals shorter than 6 months had pooled adjusted odds ratios of 1.40 for preterm birth, 1.61 for low birth weight and 1.26 for small for gestational age, and intervals of 6 to 17 months were also associated with higher risk. The authors conclude that intervals shorter than 18 months are associated with increased risk of adverse perinatal outcomes; the same paper also reports higher risk for intervals longer than 59 months, which is outside this record. The abstract does not define how the interval is measured and notes uncertainty about confounding. Only the PubMed abstract was read.

Definition

An interval between pregnancies (interpregnancy interval) shorter than 18 months. The 2006 meta-analysis compared intervals shorter than 6 months and 6 to 17 months with an interval of 18 to 23 months.

Type: Exposure

Contexts

Context Pregnancies after different intervals since the last pregnancy, 2006 meta-analysis of 67 articles

Recipient: Mixed recipients
Population: Pregnancies grouped by the interpregnancy interval that came before them, in 67 cohort, cross-sectional and case-control studies that adjusted for at least maternal age and socioeconomic status. The exposure is the mother's interval between pregnancies. The outcomes are preterm birth, low birth weight and small for gestational age, which describe the birth and the baby, so the recipient is recorded as mixed.
Care setting: Not stated in the PubMed abstract
Geography: Not stated in the PubMed abstract (studies in any language)
Life stage: Interval between pregnancies, then the outcome of the next pregnancy and birth
Gestational age: Not reported
Postnatal age: Not reported
Follow-up: Not applicable: observational studies, searched to January 2006

Eligibility: 1 inclusion criterion; 1 exclusion criterion

Included: Cohort, cross-sectional or case-control studies whose results were adjusted for at least maternal age and socioeconomic status and that gave risk estimates with 95% confidence intervals (or data to compute them) for birth spacing and perinatal outcomes
Excluded: Not stated in the PubMed abstract

Claims and evidence

Context Pregnancies after different intervals since the last pregnancy, 2006 meta-analysis of 67 articles

Recipient: Mixed recipients
Population: Pregnancies grouped by the interpregnancy interval that came before them, in 67 cohort, cross-sectional and case-control studies that adjusted for at least maternal age and socioeconomic status. The exposure is the mother's interval between pregnancies. The outcomes are preterm birth, low birth weight and small for gestational age, which describe the birth and the baby, so the recipient is recorded as mixed.
Care setting: Not stated in the PubMed abstract
Geography: Not stated in the PubMed abstract (studies in any language)
Life stage: Interval between pregnancies, then the outcome of the next pregnancy and birth
Gestational age: Not reported
Postnatal age: Not reported
Follow-up: Not applicable: observational studies, searched to January 2006

Eligibility: 1 inclusion criterion; 1 exclusion criterion

Included: Cohort, cross-sectional or case-control studies whose results were adjusted for at least maternal age and socioeconomic status and that gave risk estimates with 95% confidence intervals (or data to compute them) for birth spacing and perinatal outcomes
Excluded: Not stated in the PubMed abstract

Description Evidence synthesis Certainty not assessed

A 2006 meta-analysis in JAMA included 67 of the 130 articles it identified and compared interpregnancy intervals with an interval of 18 to 23 months. For an interval under 6 months, the pooled adjusted odds ratios [95% confidence intervals] were 1.40 [1.24 to 1.58] for preterm birth, 1.61 [1.39 to 1.86] for low birth weight and 1.26 [1.18 to 1.33] for small for gestational age. Intervals of 6 to 17 months, and intervals over 59 months, were also significantly associated with higher risk for all three outcomes. The authors concluded that intervals under 18 months, and over 59 months, are significantly associated with a higher risk of adverse perinatal outcomes.
Applies to Mixed recipients
- Pregnancies grouped by the interpregnancy interval that came before them, in 67 cohort, cross-sectional and case-control studies that adjusted for at least maternal age and socioeconomic status. The exposure is the mother's interval between pregnancies. The outcomes are preterm birth, low birth weight and small for gestational age, which describe the birth and the baby, so the recipient is recorded as mixed.
- Not stated in the PubMed abstract
- Not stated in the PubMed abstract (studies in any language)
- Interval between pregnancies, then the outcome of the next pregnancy and birth
- Gestational age Not reported
- Postnatal age Not reported
Follow-up Not applicable: observational studies, searched to January 2006
Certainty method
Not assessed

Limitations
These are associations from observational studies, not proof that a short interval causes the outcomes. The abstract says it was uncertain whether the association is confounded by maternal characteristics or socioeconomic status; the included studies were adjusted for at least maternal age and socioeconomic status. The search ended in January 2006, and the odds ratios compare with a reference interval of 18 to 23 months, not with no interval. Only the PubMed abstract was read.

Last checked
2026-10-15

Next evidence check due
Not scheduled
Sources and citations (6)
1. Supports Birth spacing and risk of adverse perinatal outcomes: a meta-analysis
  
  Publication · JAMA · Edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, retrieved 2026-10-15. The full text and the version of record were not read. · Published 2006-04-19 · DOI: 10.1001/jama.295.15.1809 · PMID: 16622143
  
  Locator
  Abstract, DATA SYNTHESIS, sentence 2, fragment 1 of 2
  
  How it applies
  PubMed abstract of the JAMA 2006 meta-analysis.
  
  Retrieved
  2026-10-15T13:49:16Z
  
  Source effective date
  Not reported
  
  Source state
  Current
  
  Snapshot hash
  e9735abf60a0d1ec5f087ff9ac0decf857621a90cdc72af79b782e03ca6bac0b
  
  Reuse basis
  PubMed record fetched through NCBI E-utilities. Only the hash of the bytes is kept, because publisher copyright may apply to the abstract (https://pubmed.ncbi.nlm.nih.gov/disclaimer/). Short factual quotations under 25 words, with the citation.
2. Supports Birth spacing and risk of adverse perinatal outcomes: a meta-analysis
  
  Publication · JAMA · Edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, retrieved 2026-10-15. The full text and the version of record were not read. · Published 2006-04-19 · DOI: 10.1001/jama.295.15.1809 · PMID: 16622143
  
  Locator
  Abstract, DATA SYNTHESIS, sentence 2, fragment 2 of 2
  
  How it applies
  PubMed abstract.
  
  Retrieved
  2026-10-15T13:49:16Z
  
  Source effective date
  Not reported
  
  Source state
  Current
  
  Snapshot hash
  e9735abf60a0d1ec5f087ff9ac0decf857621a90cdc72af79b782e03ca6bac0b
  
  Reuse basis
  PubMed record fetched through NCBI E-utilities. Only the hash of the bytes is kept, because publisher copyright may apply to the abstract (https://pubmed.ncbi.nlm.nih.gov/disclaimer/). Short factual quotations under 25 words, with the citation.
3. Supports Birth spacing and risk of adverse perinatal outcomes: a meta-analysis
  
  Publication · JAMA · Edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, retrieved 2026-10-15. The full text and the version of record were not read. · Published 2006-04-19 · DOI: 10.1001/jama.295.15.1809 · PMID: 16622143
  
  Locator
  Abstract, DATA SYNTHESIS, sentence 3, fragment 1 of 2
  
  How it applies
  PubMed abstract.
  
  Retrieved
  2026-10-15T13:49:16Z
  
  Source effective date
  Not reported
  
  Source state
  Current
  
  Snapshot hash
  e9735abf60a0d1ec5f087ff9ac0decf857621a90cdc72af79b782e03ca6bac0b
  
  Reuse basis
  PubMed record fetched through NCBI E-utilities. Only the hash of the bytes is kept, because publisher copyright may apply to the abstract (https://pubmed.ncbi.nlm.nih.gov/disclaimer/). Short factual quotations under 25 words, with the citation.
4. Supports Birth spacing and risk of adverse perinatal outcomes: a meta-analysis
  
  Publication · JAMA · Edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, retrieved 2026-10-15. The full text and the version of record were not read. · Published 2006-04-19 · DOI: 10.1001/jama.295.15.1809 · PMID: 16622143
  
  Locator
  Abstract, CONCLUSIONS, sentence 1
  
  How it applies
  PubMed abstract.
  
  Retrieved
  2026-10-15T13:49:16Z
  
  Source effective date
  Not reported
  
  Source state
  Current
  
  Snapshot hash
  e9735abf60a0d1ec5f087ff9ac0decf857621a90cdc72af79b782e03ca6bac0b
  
  Reuse basis
  PubMed record fetched through NCBI E-utilities. Only the hash of the bytes is kept, because publisher copyright may apply to the abstract (https://pubmed.ncbi.nlm.nih.gov/disclaimer/). Short factual quotations under 25 words, with the citation.
5. Background Birth spacing and risk of adverse perinatal outcomes: a meta-analysis
  
  Publication · JAMA · Edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, retrieved 2026-10-15. The full text and the version of record were not read. · Published 2006-04-19 · DOI: 10.1001/jama.295.15.1809 · PMID: 16622143
  
  Locator
  Abstract, STUDY SELECTION, sentence 2
  
  How it applies
  How many articles were included.
  
  Retrieved
  2026-10-15T13:49:16Z
  
  Source effective date
  Not reported
  
  Source state
  Current
  
  Snapshot hash
  e9735abf60a0d1ec5f087ff9ac0decf857621a90cdc72af79b782e03ca6bac0b
  
  Reuse basis
  PubMed record fetched through NCBI E-utilities. Only the hash of the bytes is kept, because publisher copyright may apply to the abstract (https://pubmed.ncbi.nlm.nih.gov/disclaimer/). Short factual quotations under 25 words, with the citation.
6. Background Birth spacing and risk of adverse perinatal outcomes: a meta-analysis
  
  Publication · JAMA · Edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, retrieved 2026-10-15. The full text and the version of record were not read. · Published 2006-04-19 · DOI: 10.1001/jama.295.15.1809 · PMID: 16622143
  
  Locator
  Abstract, CONTEXT, sentence 2
  
  How it applies
  The confounding question the abstract raises.
  
  Retrieved
  2026-10-15T13:49:16Z
  
  Source effective date
  Not reported
  
  Source state
  Current
  
  Snapshot hash
  e9735abf60a0d1ec5f087ff9ac0decf857621a90cdc72af79b782e03ca6bac0b
  
  Reuse basis
  PubMed record fetched through NCBI E-utilities. Only the hash of the bytes is kept, because publisher copyright may apply to the abstract (https://pubmed.ncbi.nlm.nih.gov/disclaimer/). Short factual quotations under 25 words, with the citation.

Clinical links

Each link reports what one cited claim says about one population. "Evaluated for" means studied, not shown to work. These links do not show that anything is effective or right for you.

Claim, not a settled fact Association in a 2006 meta-analysis of observational studies: intervals shorter than 6 months compared with 18 to 23 months (pooled adjusted odds ratio 1.40): Preterm birth (Associated with a higher risk of)
Applies to Mixed recipients
- Pregnancies grouped by the interpregnancy interval that came before them, in 67 cohort, cross-sectional and case-control studies that adjusted for at least maternal age and socioeconomic status. The exposure is the mother's interval between pregnancies. The outcomes are preterm birth, low birth weight and small for gestational age, which describe the birth and the baby, so the recipient is recorded as mixed.
- Not stated in the PubMed abstract
- Not stated in the PubMed abstract (studies in any language)
- Interval between pregnancies, then the outcome of the next pregnancy and birth
- Gestational age Not reported
- Postnatal age Not reported
Follow-up Not applicable: observational studies, searched to January 2006
A 2006 meta-analysis in JAMA included 67 of the 130 articles it identified and compared interpregnancy intervals with an interval of 18 to 23 months. For an interval under 6 months, the pooled adjusted odds ratios [95% confidence intervals] were 1.40 [1.24 to 1.58] for preterm birth, 1.61 [1.39 to 1.86] for low birth weight and 1.26 [1.18 to 1.33] for small for gestational age. Intervals of 6 to 17 months, and intervals over 59 months, were also significantly associated with higher risk for all three outcomes. The authors concluded that intervals under 18 months, and over 59 months, are significantly associated with a higher risk of adverse perinatal outcomes.
Limitations. These are associations from observational studies, not proof that a short interval causes the outcomes. The abstract says it was uncertain whether the association is confounded by maternal characteristics or socioeconomic status; the included studies were adjusted for at least maternal age and socioeconomic status. The search ended in January 2006, and the odds ratios compare with a reference interval of 18 to 23 months, not with no interval. Only the PubMed abstract was read.

Record details

Record id: maternal:short-interpregnancy-interval
Content hash: 6e5212c27e37971c1302dcf893cd5e2d140840c7a3848fb4662802526dbe230b