Understanding Preterm, Late Preterm, and Full Term Birth

Bleeding during pregnancy can be a sign of a placental complication known as placenta praevia. This condition occurs when the placenta implants low in the uterus and may partially or completely block the cervix. In this guide, we cover the definition of placenta praevia, common symptoms, and how it is managed.

What is placenta praevia?

Placenta praevia occurs when the placenta attaches close to or completely covers the cervix, making vaginal birth difficult or impossible. It is sometimes referred to as a low-lying placenta. It affects approximately 0.3-0.5% of pregnancies in Australia.

Placenta praevia is usually identified before labour begins through routine prenatal care and ultrasound scans.

Placenta praevia is typically diagnosed during the standard 18-20 week morphology ultrasound scan.

While it is often detected at 20 weeks, in approximately 90% of cases the placenta moves upwards and away from the cervix as the uterus grows, resolving on its own by the third trimester.

If a low-lying placenta is found during the 20-week scan, follow-up scans are usually scheduled at around 32-34 weeks to recheck its position.

What Is Gestational Age?

Gestational age is measured from the first day of the pregnant person’s last menstrual period and can be refined through early ultrasound, which provides the most accurate estimate of how far along the pregnancy is.

Knowing this timing is vital for your baby’s health because foetal organs and body systems develop in a predictable sequence, and gestational age helps healthcare providers understand whether growth is on track, identify potential risks, and make decisions about monitoring or intervention.

It also guides care at birth, as babies born earlier may need additional support with breathing, feeding, or temperature regulation, while those born at full term are typically more developmentally prepared for life outside the womb.

Preterm birth (before 37 weeks)

Babies born preterm are grouped into three categories based on how early they arrive:

• Extremely preterm: born before 28 weeks
• Very preterm: born between 28 and 32 weeks
• Moderate to late preterm: born between 32 and 37 weeks

Late preterm birth (34-36 weeks)

Late preterm babies born between 34 and 36 weeks often appear healthy and close to full-term size, but they can still have immature organs and systems that affect feeding, breathing, temperature regulation, and blood sugar stability.

As a result, they may face challenges such as difficulty latching or staying awake for feeds, jaundice, low blood sugar, or mild respiratory issues.

These babies often need extra monitoring, support with feeding, and help maintaining body temperature to safely transition to life outside the womb. Because they can look similar to full-term newborns, their additional needs are sometimes underestimated.

Australian neonatal guidelines highlight the importance of recognising late preterm birth as a distinct risk group, requiring tailored feeding plans, careful discharge planning, and follow-up to reduce avoidable readmissions.

Early term birth (37-38 weeks)

Early term babies born at 37-38 weeks are not considered fully mature because important fetal development continues until at least 39 weeks.

National data indicate that early term births are increasingly common in Australia. Babies born in this window have higher rates of short-term complications compared with those born at 39-40 weeks, including respiratory issues, feeding difficulties, hypoglycaemia, and higher rates of neonatal nursery admission.

Full-term birth (39-40 weeks)

Full-term birth at 39-40 weeks is considered ideal because research shows this timing gives babies the best start.

There are significantly lower rates of respiratory and feeding problems and fewer admissions to special care nurseries compared with births at 37-38 weeks.

Initiatives such as Every Week Counts emphasise that babies continue critical brain growth right up to 40 weeks, resulting in more mature brain function and improved early childhood outcomes.

Late-term birth (41 weeks)

When pregnancy extends into 41 weeks, clinicians increase monitoring to ensure the baby continues to receive enough oxygen and nutrients.

This typically includes twice-weekly cardiotocographs (CTGs) and amniotic fluid assessments to track fetal wellbeing and detect early signs of compromise.

At this stage, many hospitals begin discussing induction, as the risk of complications such as reduced placental function or low amniotic fluid starts to rise.

Most guidelines recommend planning a birth by 42 weeks unless there is a compelling reason to continue the pregnancy.

Post-term birth (42 weeks and beyond)

Post-term pregnancy, defined as 42 weeks or beyond, carries increasing risks because the placenta may no longer function as effectively.

This can reduce the baby’s oxygen and nutrient supply and increase the likelihood of complications such as stillbirth, low amniotic fluid, and the need for neonatal intensive care.

To manage these risks, doctors increase monitoring through regular CTGs, ultrasound checks, and fetal wellbeing assessments.

Induction of labour is commonly recommended at this stage, as evidence shows that delivery around 41-42 weeks is safer than continuing the pregnancy beyond this point.

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