O&G · Antenatal care — timing of birth
Post-term pregnancy
Also known as Post-dates pregnancy · Prolonged pregnancy · Post-term · Late-term pregnancy · Postmaturity
Exam-exhaustive FRANZCOG fellowship reference on post-term pregnancy — the definition (42+0 weeks), the steeply rising stillbirth risk by gestation (Muglu meta-analysis), the induction-versus-expectant evidence (Cochrane, ARRIVE and its critiques), the NICE/ACOG/RANZCOG positions, membrane sweeping, the post-dates surveillance debate, and the structured counselling of the woman declining induction. RANZCOG-primary, globally tagged to MRCOG and ABOG.
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- The stillbirth risk is non-linear — it climbs slowly to 40 weeks then accelerates; treat 42 weeks as a ceiling, not a target
- Most 'post-term' pregnancies are a dating error — confirm gestational age with the first-trimester dating scan before acting on it
- A reassuring CTG does not exclude stillbirth in the days that follow — surveillance reduces but does not eliminate the risk
- The woman who declines induction needs enhanced surveillance and a documented ceiling for expectant management
- The ARRIVE trial is not a mandate to induce every nullip at 39 weeks — generalisability and counselling intensity limit routine rollout
She is 41+3, low-risk, and she has not laboured. She sits across the desk and asks the question that decides the next two weeks: "Do I have to be induced?" Your answer is not a single sentence — it is a risk conversation, an evidence conversation, and a values conversation, and the examiner wants to hear that you can hold all three. Post-term is the topic that rewards the registrar who can quote the stillbirth curve, defend the induction evidence, counsel the woman who declines, and never confuse late-term with post-term.[1][6]
Overview and definition
Post-term (prolonged) pregnancy is defined as a gestation of 42+0 weeks (294 days) and beyond, regardless of the outcome. The single most common error at the station is conflating it with late-term pregnancy, which is the week before it.[6]
- Late term: 41+0 to 41+6 weeks.
- Post-term: 42+0 weeks and beyond (294 days from the first day of the last menstrual period, or the equivalent by dating scan).[6]
The reason the distinction matters is that risk accrues across the whole of late pregnancy — it does not switch on at 42 weeks. Treat 42 weeks as a ceiling you do not cross lightly, not a threshold you wait for.[1]
One framing anchors the entire topic: a pregnancy that reaches 42 weeks is almost always either a dating error or a true biological prolongation, and your first move is to find out which.[6]
References8ShowHide
- [1]Muglu J, Rather H, Arroyo-Manzano D, et al. Risks of stillbirth and neonatal death with advancing gestation at term: a systematic review and meta-analysis of cohort studies of 15 million pregnancies PLoS Med, 2019.PMID 31265456
- [2]Gülmezoglu AM, Crowther CA, Middleton P, Heatley E Induction of labour for improving birth outcomes for women at or beyond term Cochrane Database Syst Rev, 2012.PMID 22696345
- [3]Grobman WA, Rice MM, Reddy UM, et al. Labor Induction versus Expectant Management in Low-Risk Nulliparous Women N Engl J Med, 2018.PMID 30089070
- [4]James-Conterelli S, Kennedy HP Does the ARRIVE trial merit changing obstetric practice? Some reflections four-year postrelease Birth, 2023.PMID 36896922
- [5]American College of Obstetricians and Gynecologists Management of Full-Term Nulliparous Individuals Without a Medical Indication for Delivery: ACOG Clinical Practice Update Obstet Gynecol, 2025.PMID 39513607
- [6]American College of Obstetricians and Gynecologists ACOG Practice Bulletin Number 55: Management of Postterm Pregnancy Obstet Gynecol, 2004.PMID 15339790
- [7]Keulen JKJ, Bruinsma A, Kortekaas JC, van Dillen J, et al. Timing induction of labour at 41 or 42 weeks? A closer look at time frames of comparison: a review Midwifery, 2018.PMID 30170263
- [8]Finucane EM, Murphy DJ, Biesty LM, et al. Membrane sweeping for induction of labour Cochrane Database Syst Rev, 2020.PMID 32103497