Nulliparity

NICE uses the term nulliparity without defining it. MeSH files it under parity, which MeSH defines as "The number of offspring a female has borne." NICE lists it as one of six moderate risk factors for pre-eclampsia. Having more than one of these factors is a reason NICE gives for advising low-dose aspirin. NICE does not say how much nulliparity raises the risk by itself.

Risk factor
In this atlas

Overview

Technical summary

A trait of the pregnant woman. The NICE NG133 page does not define nulliparity. In August 2022 NICE changed the wording of recommendation 1.1.3 from first pregnancy to nulliparity, so the two terms must not be treated as the same. MeSH defines parity as the number of offspring a female has borne, and files nulliparity under it with no definition of its own. WHO 2021 uses a different term, primiparity, in its own moderate-risk list, and this record does not treat primiparity and nulliparity as the same.

Definition

MeSH defines parity as "The number of offspring a female has borne." and lists nulliparity as a narrower concept of parity without a definition of its own. NICE gives no definition.

Type: Trait

Contexts

Context Nulliparity as one moderate risk factor for pre-eclampsia (NICE NG133 recommendation 1.1.3)

Recipient: Maternal
Population: Pregnant women with nulliparity, one of six factors that NICE lists as indicating moderate risk of pre-eclampsia. The NICE page does not define nulliparity.
Care setting: Not stated in the source.
Geography: England. NICE's terms and conditions present the information on its websites as support for people in England who make decisions about funding care (clause 6) and say it is not written as a basis for decisions outside the United Kingdom (clause 8). The guideline page states no jurisdiction of its own.
Life stage: Pregnancy. The source gives no gestational age for the risk factor itself.
Gestational age: Not reported
Postnatal age: Not reported
Follow-up: Not applicable (risk factor context)

Eligibility: 1 inclusion criterion; 1 exclusion criterion

Included: Pregnant woman with nulliparity
Excluded: Not stated in the recommendation text

Claims and evidence

Context Nulliparity as one moderate risk factor for pre-eclampsia (NICE NG133 recommendation 1.1.3)

Recipient: Maternal
Population: Pregnant women with nulliparity, one of six factors that NICE lists as indicating moderate risk of pre-eclampsia. The NICE page does not define nulliparity.
Care setting: Not stated in the source.
Geography: England. NICE's terms and conditions present the information on its websites as support for people in England who make decisions about funding care (clause 6) and say it is not written as a basis for decisions outside the United Kingdom (clause 8). The guideline page states no jurisdiction of its own.
Life stage: Pregnancy. The source gives no gestational age for the risk factor itself.
Gestational age: Not reported
Postnatal age: Not reported
Follow-up: Not applicable (risk factor context)

Eligibility: 1 inclusion criterion; 1 exclusion criterion

Included: Pregnant woman with nulliparity
Excluded: Not stated in the recommendation text

Description Guidance Certainty not assessed

NICE lists nulliparity as one of six factors that indicate moderate risk of pre-eclampsia, alongside age 40 years or older, a pregnancy interval of more than 10 years, a body mass index of 35 kg/m2 or more at the first visit, a family history of pre-eclampsia and a multi-fetal pregnancy. NICE advises aspirin for women who have more than one of these factors.
Applies to Maternal
- Pregnant women with nulliparity, one of six factors that NICE lists as indicating moderate risk of pre-eclampsia. The NICE page does not define nulliparity.
- Not stated in the source.
- England. NICE's terms and conditions present the information on its websites as support for people in England who make decisions about funding care (clause 6) and say it is not written as a basis for decisions outside the United Kingdom (clause 8). The guideline page states no jurisdiction of its own.
- Pregnancy. The source gives no gestational age for the risk factor itself.
- Gestational age Not reported
- Postnatal age Not reported
Follow-up Not applicable (risk factor context)
Certainty method
Not assessed

Limitations
NICE does not say how much nulliparity raises the risk by itself, and the NICE page does not define the term, so no risk figure is recorded. In August 2022 NICE corrected the wording of recommendation 1.1.3 from first pregnancy to nulliparity, so the two terms must not be used as if they meant the same. WHO 2021 uses a different term, primiparity, in its own moderate-risk list. A list of risk factors is not an estimate of risk for any one woman.

Last checked
2026-10-11

Next evidence check due
Not scheduled
Sources and citations (4)
1. Supports Hypertension in pregnancy: diagnosis and management (NICE guideline NG133), Recommendations chapter
  
  Guideline · National Institute for Health and Care Excellence (NICE) · Edition The version shown on 2026-10-11, with a page header that gives 17 April 2023 as the last update. The same bytes came back on a second fetch minutes later. · Published 2019-06-25 · nice: NG133
  
  Locator
  1.1.3, moderate-risk list, items 1 to 3
  
  How it applies
  NICE NG133, cited and linked only. Nulliparity is the first item of the list.
  
  Retrieved
  2026-10-11T18:19:40Z
  
  Source effective date
  2023-04-17
  
  Source state
  Current
  
  Snapshot hash
  0cd8548f5807f03a82b3101dc56ebadf674106da9d0aa7e57955d4a823556fca
  
  Reuse basis
  The page bytes are not committed. Public text is cite_only (Ben's decision of 2026-10-13 (medical-atlas-core issue 2)): public pages state the facts in the atlas's own words, with a citation and a link, and use no NICE wording. NICE reuse terms, read on 2026-10-11: the NICE UK Open Content Licence covers use in a UK setting only, international use outside personal research and study needs a licence and a fee, and the NICE terms and conditions make content available for artificial intelligence purposes only through an approval process, a licence and a fee for international use. This pipeline uses AI agents to read the page, so Ben decided on 2026-10-13 that public pages cite and link NICE and use none of its wording.
2. Supports Hypertension in pregnancy: diagnosis and management (NICE guideline NG133), Recommendations chapter
  
  Guideline · National Institute for Health and Care Excellence (NICE) · Edition The version shown on 2026-10-11, with a page header that gives 17 April 2023 as the last update. The same bytes came back on a second fetch minutes later. · Published 2019-06-25 · nice: NG133
  
  Locator
  1.1.3, moderate-risk list, items 4 to 6 and recommendation tag
  
  How it applies
  The other three moderate risk factors.
  
  Retrieved
  2026-10-11T18:19:40Z
  
  Source effective date
  2023-04-17
  
  Source state
  Current
  
  Snapshot hash
  0cd8548f5807f03a82b3101dc56ebadf674106da9d0aa7e57955d4a823556fca
  
  Reuse basis
  The page bytes are not committed. Public text is cite_only (Ben's decision of 2026-10-13 (medical-atlas-core issue 2)): public pages state the facts in the atlas's own words, with a citation and a link, and use no NICE wording. NICE reuse terms, read on 2026-10-11: the NICE UK Open Content Licence covers use in a UK setting only, international use outside personal research and study needs a licence and a fee, and the NICE terms and conditions make content available for artificial intelligence purposes only through an approval process, a licence and a fee for international use. This pipeline uses AI agents to read the page, so Ben decided on 2026-10-13 that public pages cite and link NICE and use none of its wording.
3. Background Hypertension in pregnancy: diagnosis and management (NICE guideline NG133), Update information chapter
  
  Guideline · National Institute for Health and Care Excellence (NICE) · Edition The Update information chapter of NICE guideline NG133, as shown on 2026-10-11 with the page header Last updated: 17 April 2023. It lists what changed in June 2019, the minor changes after publication (August 2022, April 2023 and October 2023) and the guideline ISBN. The chapter has no identifier of its own because the Recommendations chapter source already holds the identifier NG133. Cluster B and cluster C fetched this page separately on 2026-10-11 and both returned the same bytes (sha256 248348547ec88c3384b6fb76489a433766acf40e47b5f77d8060516561836a58). The integration step kept this one source and snapshot and redirected the cluster C citations to them. · Published 2019-06-25
  
  Locator
  Minor changes since publication, August 2022
  
  How it applies
  NICE's own correction of the term in recommendation 1.1.3.
  
  Retrieved
  2026-10-11T19:16:21Z
  
  Source effective date
  2023-04-17
  
  Source state
  Current
  
  Snapshot hash
  248348547ec88c3384b6fb76489a433766acf40e47b5f77d8060516561836a58
  
  Reuse basis
  The page bytes are not committed. Public text is cite_only (Ben's decision of 2026-10-13 (medical-atlas-core issue 2)): public pages state the facts in the atlas's own words, with a citation and a link, and use no NICE wording. NICE reuse terms, read on 2026-10-11 and recorded in research/setup/notes.md: the NICE UK Open Content Licence covers use in a UK setting only, international use outside personal research and study needs a licence and a fee, and the NICE terms and conditions make content available for artificial intelligence purposes only through an approval process, a licence and a fee for international use. This pipeline uses AI agents to read the page, so Ben decided on 2026-10-13 that public pages cite and link NICE and use none of its wording.
4. Background MeSH concept M0015959 (Parity)
  
  Dataset · U.S. National Library of Medicine · Edition MeSH linked-data concept record as fetched on 2026-10-11. It holds the scope note and the list of narrower concepts, and states no date. · mesh-concept: M0015959
  
  Locator
  scopeNote.@value, sentence 1
  
  How it applies
  MeSH definition of parity, the term that groups nulliparity. It is not a definition of nulliparity itself.
  
  Retrieved
  2026-10-11T19:15:23Z
  
  Source effective date
  Not reported
  
  Source state
  Current
  
  Snapshot hash
  aa475bcc0d87b166a854aa3561a27082f8367683a553c1373d3e85a550aeadf4
  
  Reuse basis
  The NLM web policies page (fetched as mc-nlm-web-policies.html, sha256 c8b7026b5c3fcfd1b0cb88755077f6a99a5f2159eecd42b0e7d1a5ad9b30ec55) says works produced by the U.S. government are not subject to copyright protection in the United States and asks users to acknowledge NLM as the source. Source: National Library of Medicine. The NLM terms and conditions page (mc-nlm-terms.html, sha256 f1fb494447a54d2190e496410163c8e1fc138a601d83d8c124f267f7103026b3) asks redistributors to maintain the most current data or to make known clearly that their copy may not reflect the most current data available from NLM. This copy was fetched on 2026-10-11 and may not reflect the most current data. The raw bytes are committed at research/snapshots/mc-mesh-M0015959.json.

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 NICE NG133 lists it as one of six moderate risk factors for pre-eclampsia; the guideline gives no risk figure: Pre-eclampsia (Associated with a higher risk of)
Applies to Maternal
- Pregnant women with nulliparity, one of six factors that NICE lists as indicating moderate risk of pre-eclampsia. The NICE page does not define nulliparity.
- Not stated in the source.
- England. NICE's terms and conditions present the information on its websites as support for people in England who make decisions about funding care (clause 6) and say it is not written as a basis for decisions outside the United Kingdom (clause 8). The guideline page states no jurisdiction of its own.
- Pregnancy. The source gives no gestational age for the risk factor itself.
- Gestational age Not reported
- Postnatal age Not reported
Follow-up Not applicable (risk factor context)
NICE lists nulliparity as one of six factors that indicate moderate risk of pre-eclampsia, alongside age 40 years or older, a pregnancy interval of more than 10 years, a body mass index of 35 kg/m2 or more at the first visit, a family history of pre-eclampsia and a multi-fetal pregnancy. NICE advises aspirin for women who have more than one of these factors.
Limitations. NICE does not say how much nulliparity raises the risk by itself, and the NICE page does not define the term, so no risk figure is recorded. In August 2022 NICE corrected the wording of recommendation 1.1.3 from first pregnancy to nulliparity, so the two terms must not be used as if they meant the same. WHO 2021 uses a different term, primiparity, in its own moderate-risk list. A list of risk factors is not an estimate of risk for any one woman.

Record details

Record id: maternal:nulliparity
Content hash: a508fe3aea2fd347e181c525e3b9c169d612509e9165023988c02a4e82758f2d