Prolonged Pregnancy
Published: 01 June 2023
Published: 01 June 2023
Prolonged pregnancy is a pregnancy that extends to 42 weeks of gestation or beyond (DoHaAC 2022).
In Australia, it’s estimated that about 4 per 1,000 babies are born post-term (Pregnancy, Birth and Baby 2022).
The estimated date of confinement (EDC) (estimated due date) for a pregancy is typically calculated using first day of the patient’s last menstrual period and their typical menstrual cycle duration (Pregnancy, Birth and Baby 2021).
For patients with irregular menstrual cycles, the EDC might be difficult to calculate. Other factors that may be taken into consideration include:
(Better Health Channel 2014)
The most common cause of prolonged pregnancy is inaccurate dating based on the patient’s last menstrual period (Norwitz 2022).
In pregnancies that are dated accurately, the cause of prolonged pregnancy is often unknown (Norwitz 2022). However, there are factors that are known to contribute to prolonged pregnancy. These include:
(Pregnancy, Birth and Baby 2022)
A key danger of prolonged pregnancy is the increased risk of fetal and neonatal complications.
The perinatal mortality rate has been shown to increase post-term. In 2016, the perinatal death rate in Australia was 1.5 per 1,000 births for babies born at 37 to 41 weeks. This increased to 2.2 per 1,000 births after 41 weeks (DoHaAC 2022).
About 20% of post-term fetuses are thought to have dysmaturity syndrome, where infants have characteristics resembling chronic intrauterine growth restriction from uteroplacental insufficiency (Caughey 2021). These characteristics include:
As a post-term fetus has continued to grow beyond the EDC, they are at increased risk of complications related to larger body size and macrosomia (weighing more than 4500 grams). These complications can include:
(Norwitz 2022)
Post-term fetuses are more likely to pass meconium into the amniotic fluid. This stained fluid can then be inhaled by the fetus, causing breathing difficulties (Norwitz 2022).
(Caughey 2021)
(Norwitz 2022; Caughey 2021)
Management might include:
(Norwitz 2022; DoHaAC 2022)
When a patient is nearing prolonged pregnancy, it’s important to have a discussion with them, explaining the risks and benefits of different management options and establishing their preferences.
You should discuss the following:
(DoHaAC 2022)
It’s important to take a holistic approach to this discussion, taking into consideration factors such as logistics (e.g. has the patient travelled to give birth) and the need for community supports (e.g. financial assistance) (DoHaAC 2022).