Gravidity and parity
In biology and human medicine, gravidity and parity are the number of times a woman is or has been pregnant (gravidity) and carried the pregnancies to a viable gestational age (parity). These terms are usually coupled, sometimes with additional terms, to indicate more details of the woman's obstetric history. When using these terms:
- Gravida indicates the number of times a woman is or has been pregnant, regardless of the pregnancy outcome. A current pregnancy, if any, is included in this count. Multiple pregnancy is counted as 1.
- Parity, or "para", indicates the number of pregnancies reaching viable gestational age (including live births and stillbirths). The number of fetuses does not determine the parity. Twin pregnancy carried to viable gestational age is counted as 1.
- Abortus is the number of pregnancies that were lost for any reason, including induced abortions or miscarriages. The abortus term is sometimes dropped when no pregnancies have been lost. Stillbirths are not included.
Gravidity in humans
- The term "gravida" can be used to refer to a pregnant woman.
- A "nulligravida" is a woman who has never been pregnant.
- A "primigravida" is a woman who is pregnant for the first time or has been pregnant once.
- A "multigravida" or "secundigravida" is a woman who has been pregnant more than once.
Terms such as "gravida 0", referring to a nulligravida, "gravida 1" for a primigravida, and so on, can also be used. The term "elderly primigravida" has also been used to refer to a woman in their first pregnancy who is at least 35 years old. Advanced maternal age can be a risk factor for some birth defects.
Gravidity in biology
In biology, the term "gravid" (Latin: gravidus "burdened, heavy") is used to describe the condition of an animal (most commonly fish or reptiles) when carrying eggs internally. For example, Astatotilapia burtoni females can transform between reproductive states, one of which is gravid, and the other non-gravid. In entomology it describes a mated female insect.
In human medicine, parity is the number of pregnancies carried by a woman for at least 20 weeks (duration varies from region to region, 20 – 28 weeks, depending upon age of viability). If a woman carries the fetus to viable age, even if ultimately the fetus is born deceased, this still counts as an instance of parity, as parity is based on the time of gestation prior to a birth, and not the status of the offspring once born.  
A woman who has never carried a pregnancy beyond 20 weeks is nulliparous and is called a nullipara or para 0. A woman who has given birth once is primiparous and is referred to as a primipara or primip. A woman who has given birth two, three, or four times is multiparous and is called a multip. Grand multipara describes the condition of having given birth five or more times.
Like gravidity, parity may also be counted. A woman who has given birth one or more times can also be referred to as para 1, para 2, para 3, and so on.
Viable gestational age varies from region to region.
In agriculture, parity is a factor in productivity in domestic animals kept for milk production. Animals that have given birth once are described as "primiparous"; those that have given birth more than once are described as "pluriparous". Those that have given birth twice may also be described as "secondiparous", in which case "pluriparous" is applied to those that have given birth three times or more.
A nulliparous (//) woman (a nullipara or para 0) has never given birth. It includes women who have experienced spontaneous miscarriages and induced abortions before the mid-point of pregnancy, but not women who have experienced pregnancy loss after 20 weeks.
Long-term and permanent nulliparity (//) are risk factors for breast cancer. For instance, a meta-analysis of 8 population-based studies in the Nordic countries found that never giving birth was associated with a 30% increase in the risk of breast cancer compared with women who have given birth, and for every 2 births, the risk was reduced by about 16%. Women having their first birth after the age of 35 years had a 40% increased risk compared to those with a first birth before the age of 20 years.
A number of systems are incorporated into a woman's obstetric history to record the number of past pregnancies and pregnancies carried to viable age. These include:
- The gravida/para/abortus (GPA) system, or sometimes just gravida/para (GP), is one such shorthand. For example, the obstetric history of a woman who has had two pregnancies (both of which resulted in live births) would be noted as G2P2. The obstetric history of a woman who has had four pregnancies, one of which was a miscarriage before 20 weeks, would be noted in the GPA system as G4P3A1 and in the GP system as G4P3. The obstetric history of a woman who has had one pregnancy of twins with successful outcomes would be noted as G1P1+1.
- TPAL is one of the methods to provide a quick overview of a person's obstetric history. In TPAL, the T refers to term births (after 37 weeks' gestation), the P refers to premature births, the A refers to abortions, and the L refers to living children. When reported, the "abortions" number refers to the total number of spontaneous or induced abortions and miscarriages, including ectopic pregnancies, prior to 20 weeks. If a fetus is aborted after 20 weeks, spontaneously or electively, then it is counted as a premature birth and P will increase but L will not. The TPAL is described by numbers separated by hyphens. Multiple births (twins, triplets and higher multiples) count as one pregnancy (gravidity) and as one birth. For example, a pregnant woman who carried one pregnancy to term with a surviving infant; carried one pregnancy to 35 weeks with surviving twins; carried one pregnancy to 9 weeks as an ectopic (tubal) pregnancy; and has three living children would have a TPAL annotation of T1, P1, A1, L3. This could also be written as 1-1-1-3.
- The term GTPAL is used when the TPAL is prefixed with gravidity, and GTPALM when GTPAL is followed by number of multiple pregnancies. For example, the gravidity and parity of a woman who has given birth at term once and has had one miscarriage at 12 weeks would be recorded as G2 T1 P0 A1 L1. This notation is not standardized and can lead to misinterpretations.
Though similar, GPA should not be confused with the TPAL system, the latter of which may be used to provide information about the number of miscarriages, preterm births, and live births by dropping the "A" from "GPA" and including four separate numbers after the "P", as in G5P3114. This TPAL form indicates five pregnancies, with three term births, one preterm birth, one induced abortion or miscarriage, and four living children.
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