Product of conception—gestational age, completed weeks N[N]

The age of a product of conception in completed weeks.

Gestational age is the best clinical estimate of the duration of pregnancy at a specific point in time, based on the first day of the last menstrual period, ultrasound or physical examination of the baby.

Gestational age is conventionally expressed in completed weeks. When gestational age is calculated using the first day of the last normal menstrual period, the first day is counted as day zero and not day one. Therefore, a 25 week, 5 day fetus is considered a 25 week fetus (25+0, 25+1, 25+2, 25+3, 25+4, 25+5, 25+6).

When ultrasound is used to date a pregnancy, the earliest ultrasound examination should be used and should preferably be between 6 and 10 weeks gestation. Scans performed beyond 24 weeks gestation are unlikely to be reliable in estimating gestational age and should not be used for this purpose.

The World Health Organization identifies the following categories for duration of gestation:

• pre-term: less than 37 completed weeks (less than 259 days) of gestation
• term: from 37 completed weeks to less than 42 completed weeks (259 to 293 days) of gestation
• post-term: 42 completed weeks or more (294 days or more) of gestation.

Gestational age is a key marker in pregnancy and an important risk factor for neonatal outcomes.

National Perinatal Data Development Committee

WHO (World Health Organization) 1992. International Classification of Diseases and Related Health Problems, 10th Revision. Geneva: WHO.

American Academy of Pediatrics 2004. Policy statement: Age terminology during the perinatal period. Paediatrics 114(5):1362–64.

See also Pregnancy—estimated duration (at the first visit for antenatal care), completed weeks N[N] Health, Superseded 12/12/2018, Indigenous, Archived 02/04/2019, ACT Health, Final 14/08/2018

See also Pregnancy—estimated duration, total weeks N[N] WA Health, Endorsed 04/03/2014

Supersedes Product of conception—gestational age, completed weeks N[N] Health, Superseded 02/08/2017, Tasmanian Health, Archived 03/07/2020

Has been superseded by Product of conception—gestational age, total completed weeks N[N] Health, Standard 12/12/2018, Tasmanian Health, Endorsed 03/07/2020

Perinatal NMDS 2018-19 Health, Superseded 12/12/2018
ACT Health, Final 14/08/2018