{
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  "id": "maternal:short-interpregnancy-interval",
  "owner": "maternal",
  "kind": "risk_factor",
  "slug": "short-interpregnancy-interval",
  "name": "Short interval between pregnancies",
  "aliases": [],
  "atlases": [
    "maternal"
  ],
  "summary_plain": "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.",
  "summary_technical": "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.",
  "editorial_state": "draft",
  "last_substantive_edit": "2026-10-15",
  "last_evidence_check": "2026-10-15",
  "next_review_due": null,
  "identifiers": [],
  "navigation": {
    "maternal": {
      "life-stage": [
        "postpartum",
        "preconception"
      ],
      "care-area": [
        "postpartum-recovery"
      ]
    }
  },
  "payload": {
    "factor_type": "exposure",
    "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.",
    "contexts": [
      "maternal:ctx-interpregnancy-interval-meta-analysis-67-articles"
    ]
  },
  "content_digest": "6e5212c27e37971c1302dcf893cd5e2d140840c7a3848fb4662802526dbe230b",
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      "owner": "maternal",
      "subject_entity_id": "maternal:short-interpregnancy-interval",
      "category": "descriptive",
      "statement": "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.",
      "context": {
        "id": "maternal:ctx-interpregnancy-interval-meta-analysis-67-articles",
        "label": "Pregnancies after different intervals since the last pregnancy, 2006 meta-analysis of 67 articles",
        "recipient": "mixed",
        "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_note": "Interval between pregnancies, then the outcome of the next pregnancy and birth",
        "life_stage_terms": {
          "maternal": [
            "postpartum",
            "preconception"
          ]
        },
        "gestational_age_min_days": null,
        "gestational_age_max_days": null,
        "gestational_age_basis": null,
        "postnatal_age_min_days": null,
        "postnatal_age_max_days": null,
        "gestational_age_status": null,
        "postnatal_age_status": null,
        "followup_description": "Not applicable: observational studies, searched to January 2006",
        "eligibility": {
          "inclusion": [
            "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"
          ],
          "exclusion": [
            "Not stated in the PubMed abstract"
          ]
        }
      },
      "evidence_stage": "synthesis",
      "certainty": "not_assessed",
      "certainty_method": null,
      "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.",
      "editorial_state": "draft",
      "checked_at": "2026-10-15",
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        "predicate": "increases_risk_of",
        "label": "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)",
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