Gravidity and Parity Definitions (and their Implications in Risk Assessment)

The shorthand system of describing gravidity and parity has evolved based on local obstetric traditions, it may vary slightly between different communities and this can cause confusion.¹

In the UK, gravidity is defined as the number of times that a woman has been pregnant and parity is defined as the number of times that she has given birth to a fetus with a gestational age of 24 weeks or more, regardless of whether the child was born alive or was stillborn.

For example, a woman who is described as "gravida 2, para 2" (sometimes abbreviated to G2 P2) has had two pregnancies and two deliveries after 24 weeks, and a woman who is described as "gravida 2, para 0 " (G2 P0) has had two pregnancies, neither of which survived to a gestational age of 24 weeks. If they are both currently pregnant again, these women would have the obstetric resumé of G3 P2 and G3 P0 respectively. Sometimes a suffix is added to indicate the number of miscarriages or terminations a woman has had. So if the second woman had had two miscarriages, it could be annotated G3 P0+2.

• A nulliparous woman (nullip) has not given birth previously (regardless of outcome).
• A primagravida is in her first pregnancy.
• A primiparous woman has given birth once. The term 'primip' is often used interchangeably with primagravida, although technically incorrect as a woman does not become primiparous until she has delivered her baby.
• A multigravida has been pregnant more than once.
• A multiparous woman (multip) has given birth more than once.
• A grand multipara is a woman who has already delivered five or more infants who have achieved a gestational age of 24 weeks or more, and such women are traditionally considered to be at higher risk than the average in subsequent pregnancies.
• A grand multigravida has been pregnant five times or more.
• A great grand multipara has delivered seven or more infants beyond 24 weeks' gestation.

Multiple pregnancies present a problem: a multiple gestation counts as a single event and a multiple birth should be interpreted as a single parous event, although this remains contentious.¹ In a survey, only 20% British midwives and obstetricians recognised a twin delivery as a single parous event - G1 P1 rather than G1 P2,² revealing the potential lack of standardisation in our documentation.

A more elaborate coding system used elsewhere, including America, is GTPAL (G=gravidity, T=term deliveries, P=preterm deliveries, A=abortions or miscarriages, L=live births).

The current total fertility rate (the average number of children a woman would have if she experienced the fertility rate of a particular year for her entire child-bearing years) stands at 1.96 (2008 figures).³ Women are commencing their child-bearing later and having fewer children in total. More women remain childless (1 in 5 of women born in 1963 compared to 1 in 8 of those born in 1933). Fewer women have 3 or more children (3 in 10 women born in 1963 compared to 4 in 10 women born in 1933). The number of higher order grand multips has fallen significantly.

Obstetric histories should always record parity, gravidity and outcomes of all previous pregnancies as:

• Outcomes of previous pregnancies give some indication of the likely outcome and degree of risk with the current pregnancy.
• The number of previous pregnancies and deliveries will also influence the risks associated with the current pregnancy.
• What is considered normal labour varies according to parity:
  • Normal labour in a primagravida is significantly different to normal labour in multiparous women, as physiologically the uterus is a less efficient organ, contractions may be dyscoordinate or hypotonic. The average first stage in a primagravida is significantly slower than in a multip (primarily due to the rate of cervical dilation)⁴ - so progress is expected to be slower but delay longer than expected should prompt augmentation in managed labour.
  • Interestingly, grand multips have a longer latent phase of labour than either nulliparous or lower-parity multiparous women but then begin to dilate more rapidly. After 6 cm dilation, partogram curves for lower parity multips and grand multips are indistinguishable. Progress of labour does not appear to continue to improve with additional child-bearing.⁵

Risks associated with nulliparity/primagravidae

• Higher risk of developing pre-eclampsia (relative risk 2.91 with confidence interval 1.28-6.61).⁶
• Delayed first stage of labour, though this could be considered normal in a primagravida.
• Dystocia (or difficult labour) was diagnosed in 37% primagravidae in one Danish study.⁷

Risks associated with grand multiparity⁸

Increased risk of:

• Abnormal fetal presentation
• Precipitate delivery
• Uterine atony
• Placenta praevia
• Uterine rupture
• Amniotic fluid embolism
• Obstetric haemorrhage
• Stress incontinence and urinary urgency symptoms⁹
• Levator ani dysfunction¹⁰

What is a high-risk pregnancy?

Risk equates to factors that increase likelihood of harm to mother or baby. There is no universally accepted definition of a 'high-risk' pregnancy and nor can antenatal 'risk' screening identify every pregnancy/labour that will run into complications. Usually risk factors are combined and weighted to try to match an appropriate level of medical care and intervention to a more risky pregnancy to attempt to reduce the chances of a poor outcome.

Confounding variables¹¹

Increased parity is often associated with:

• Increasing maternal age
• Lower socio-economic and educational status
• Poorer prenatal care (more likely to be late bookers and poor attenders)
• Smoking and alcohol consumption
• Higher BMIs
• Higher rates of gestational diabetes

It is not always possible to disassociate the various risk factors attributable to each factor. Between 1997 and 1999, the maternal mortality rate was almost 6 times greater in women of parity 4 or more, as compared to that of women in their first pregnancy.¹² However, a subsequent report discounted this apparent association between high parity and maternal mortality and the association becomes much harder to characterise as fewer and fewer women in the UK have 4 or more children into the 21st century.¹³ The lowest maternal mortality rates are observed in women with one previous pregnancy.

Primigravidae

Provide:

• Good antenatal care with particular vigilance to early warning signs of pre-eclamptic toxaemia (PET). NICE recommends nullips with uncomplicated pregnancies should have 10 routine antenatal appointments (versus 7 in parous women).¹⁴
• Good antenatal and parenting education, support during labour and pain control (if desired) are especially important in a first pregnancy as anxiety levels are likely to be high.
• Where there is delay in the first stage of labour in a primagravida, active management with artificial rupture of membranes and/or oxytocin to augment labour.¹⁵
• The second stage of labour can be allowed to continue for longer than the traditional time associated with multips, as long as fetal monitoring is satisfactory and there is ongoing fetal descent.¹⁵

Grand multigravidae

It is usually appropriate to book for delivery in a specialist unit.
Consider:

• Iron and folate prophylaxis.
• A plan for the care of existing children during admission.
• Vigilance for abnormal fetal presentations from 36 weeks onward.
• Plan for possible rapid labour and delivery.
• Monitor strength of contractions and fetal presentation during delivery.
• Planning for the possibility of postpartum haemorrhage.
• Good physiotherapy and postnatal follow-up for urogynaecological problems.

1. Creinin MD, Simhan HN; Can we communicate gravidity and parity better? Obstet Gynecol. 2009 Mar;113(3):709-11. [abstract]
2. Opara EI, Zaidi J; The interpretation and clinical application of the word 'parity': a survey. BJOG. 2007 Oct;114(10):1295-7. [abstract]
3. National statistics; Total fertility rate
4. Vahratian A, Hoffman MK, Troendle JF, et al; The impact of parity on course of labor in a contemporary population.; Birth. 2006 Mar;33(1):12-7. [abstract]
5. Gurewitsch ED, Diament P, Fong J, et al; The labor curve of the grand multipara: does progress of labor continue to improve with additional childbearing?; Am J Obstet Gynecol. 2002 Jun;186(6):1331-8. [abstract]
6. Duckitt K, Harrington D; Risk factors for pre-eclampsia at antenatal booking: systematic review of controlled studies.; BMJ. 2005 Mar 12;330(7491):565. Epub 2005 Mar 2. [abstract]
7. Kjaergaard H, Olsen J, Ottesen B, et al; Incidence and outcomes of dystocia in the active phase of labor in term nulliparous women with spontaneous labor onset. Acta Obstet Gynecol Scand. 2009;88(4):402-7. [abstract]
8. Merck Manual; Merck manual of diagnosis and therapy (on-line). Chapter 250 High risk pregnancy
9. Handa VL, Harvey L, Fox HE, et al; Parity and route of delivery: does cesarean delivery reduce bladder symptoms later in life?; Am J Obstet Gynecol. 2004 Aug;191(2):463-9. [abstract]
10. Kisli E, Kisli M, Agargun H, et al; Impaired function of the levator ani muscle in the grand multipara and great Tohoku J Exp Med. 2006 Dec;210(4):365-72. [abstract]
11. Roman H, Robillard PY, Verspyck E, et al; Obstetric and neonatal outcomes in grand multiparity.; Obstet Gynecol. 2004 Jun;103(6):1294-9. [abstract]
12. CEMACH - Why mothers die; Confidential enquiry into maternal deaths in the UK; (1997-1999)
13. CEMACH - Why mothers die; Confidential enquiry into maternal deaths in the UK. Chapter 1 - Introduction and key findings; (2000-2002).
14. Antenatal care: routine care for the healthy pregnant woman, NICE Clinical Guideline (March 2008)
15. Shields SG, Ratcliffe SD, Fontaine P, et al; Dystocia in nulliparous women. Am Fam Physician. 2007 Jun 1;75(11):1671-8. [abstract]