Pregnancy involves many changes, but one of the most important is the development of the placenta. This remarkable organ supports your baby’s growth and wellbeing throughout pregnancy, acting as the vital connection between you and your baby.
It’s common to hear terms such as anterior placenta, low-lying placenta, or placenta praevia during routine ultrasound appointments. While these findings can sometimes cause anxiety, most placental variations are completely normal and simply reflect where the placenta has attached within the uterus. [rcog.org.uk], [ranzcog.edu.au]
This guide explains what the placenta does, common placental positions, and when additional monitoring may be recommended.
What is the placenta?
The placenta is a temporary organ that develops during pregnancy and attaches to the wall of the uterus. It connects to your baby through the umbilical cord and serves as the interface between maternal and fetal circulation. Although your blood and your baby’s blood do not directly mix, the placenta allows the exchange of oxygen, nutrients and waste products that are essential for growth and development. [ranzcog.edu.au], [rcog.org.uk]
The placenta develops shortly after conception and grows alongside your baby throughout pregnancy. It is delivered shortly after birth and is often referred to as the “afterbirth”. [ranzcog.edu.au], [rcog.org.uk]
What does the placenta do?
The placenta performs several essential functions to support a healthy pregnancy.
Supplying Oxygen and Nutrients
One of the placenta’s primary roles is delivering oxygen and nutrients from your bloodstream to your baby. These nutrients support the development of your baby’s organs, brain, bones and tissues. [ranzcog.edu.au], [rcog.org.uk]
Removing Waste Products
The placenta carries carbon dioxide and other waste products away from your baby and back into your circulation so they can be eliminated by your body. [tommys.org], [ranzcog.edu.au]
Producing Hormones
The placenta produces hormones that help maintain pregnancy and support fetal growth and development. These hormones contribute to many of the physical changes experienced during pregnancy. [ranzcog.edu.au], [rcog.org.uk]
Providing Protection
While not a complete barrier, the placenta helps regulate what passes between mother and baby and plays an important role in maintaining a healthy pregnancy environment. [ranzcog.edu.au], [rcog.org.uk]
Where can the placenta be located?
The placenta can attach in various locations within the uterus. In most cases, placental position is simply a normal variation and has no impact on your baby’s growth or wellbeing. [rcog.org.uk], [ranzcog.edu.au]
Common placental positions include:
- Anterior placenta – attached to the front wall of the uterus
- Posterior placenta – attached to the back wall of the uterus
- Fundal placenta – attached near the top of the uterus
- Lateral placenta – attached on either side of the uterus
- Low-lying placenta – attached close to the cervix [rcog.org.uk], [ranzcog.edu.au]
The final location of the placenta is largely determined by where the fertilised egg implants in early pregnancy. [rcog.org.uk]
What is an anterior placenta?
An anterior placenta means the placenta is attached to the front wall of the uterus, closest to your abdomen.
This is a normal and common placental position. An anterior placenta functions exactly the same way as a placenta located elsewhere in the uterus and does not affect your baby’s growth or development. [rcog.org.uk], [ranzcog.edu.au]
How Might an Anterior Placenta Affect Pregnancy?
Most women with an anterior placenta experience healthy, uncomplicated pregnancies. [rcog.org.uk], [ranzcog.edu.au]
However, because the placenta sits between your baby and your abdominal wall, you may:
- Feel your baby’s movements slightly later than expected
- Notice movements feel softer in early pregnancy
- Find that healthcare providers need a little more time to detect the fetal heartbeat during earlier stages of pregnancy [rcog.org.uk], [ranzcog.edu.au]
Importantly, an anterior placenta is not considered a pregnancy complication and usually requires no additional monitoring beyond routine antenatal care. [rcog.org.uk], [ranzcog.edu.au]
What is a low-lying placenta?
A low-lying placenta occurs when the placenta develops near the cervix, the opening at the lower end of the uterus. In Australia, a placenta is generally considered low-lying if it is within 2 centimetres of the cervix. A placenta located more than 2 centimetres from the cervix is considered to be in a normal position. [pregnancyb…aby.org.au], [healthdirect.gov.au]
A low-lying placenta is commonly identified during the routine 20-week morphology scan. [seslhd.hea…nsw.gov.au], [rcog.org.uk]
The Reassuring News
In most cases, a low-lying placenta diagnosed in mid-pregnancy will move higher as the uterus expands.
Clinical guidance suggests that approximately 90% of low-lying placentas identified at the 20-week scan are no longer low-lying later in pregnancy. [rcog.org.uk], [tommys.org]
For this reason, follow-up ultrasound scans are typically recommended during the third trimester to reassess placental position. [rcog.org.uk], [seslhd.hea…nsw.gov.au]
What is placenta praevia?
Placenta praevia occurs when the placenta partially or completely covers the cervix. Because the cervix is the pathway through which the baby is born during a vaginal birth, a placenta covering this opening can create challenges later in pregnancy and during delivery. [ranzcog.edu.au], [pregnancyb…aby.org.au]
Placenta praevia is relatively uncommon at the end of pregnancy, affecting approximately 1 in 200 pregnancies. [rcog.org.uk], [pregnancyb…aby.org.au]
Possible Concerns Associated with Placenta Praevia
Women diagnosed with placenta praevia may have an increased risk of:
- Vaginal bleeding during pregnancy
- Bleeding during labour and birth
- Preterm birth
- Caesarean birth if the placenta continues to cover the cervix near term [ranzcog.edu.au], [pregnancyb…aby.org.au], [healthdirect.gov.au]
However, many women diagnosed with a low-lying placenta earlier in pregnancy will not go on to have placenta praevia at birth because the placenta often moves away from the cervix as the uterus grows. [rcog.org.uk], [ranzcog.edu.au]
Rare placental conditions
Placenta Accreta Spectrum
Placenta accreta spectrum refers to conditions where the placenta grows too deeply into the wall of the uterus. Although uncommon, it can increase the risk of significant bleeding during birth and requires specialist obstetric care. Previous Caesarean birth and placenta praevia are recognised risk factors. [ranzcog.edu.au], [pregnancyb…aby.org.au]
Vasa Praevia
Vasa praevia is a rare condition in which fetal blood vessels pass near the cervix without the usual protection of placental tissue or the umbilical cord. Because these vessels can be vulnerable during labour, specialist monitoring is required. [ranzcog.edu.au], [pregnancyb…aby.org.au]
How is placental position assessed?
Placental location is routinely assessed during the 18–21 week ultrasound, often referred to in Australia as the morphology scan. [seslhd.hea…nsw.gov.au], [pregnancyb…aby.org.au]
If the placenta appears low-lying, your doctor, obstetrician or midwife may recommend additional scans later in pregnancy. In some cases, a transvaginal ultrasound provides the most accurate assessment of placental position and is considered safe during pregnancy. [ranzcog.edu.au], [rcog.org.uk]
When should you seek medical advice?
Most placental variations cause no symptoms and are identified during routine ultrasounds. [rcog.org.uk], [ranzcog.edu.au]
However, you should seek medical advice promptly if you experience:
- Any vaginal bleeding during pregnancy
- Significant abdominal pain
- A noticeable reduction or change in your baby’s normal movement pattern
- Any symptoms that concern you [pregnancyb…aby.org.au], [healthdirect.gov.au], [ranzcog.edu.au]
If bleeding is heavy or accompanied by severe pain, urgent medical assessment is recommended. [pregnancyb…aby.org.au], [healthdirect.gov.au]
What’s normal and when not to worry
Many expectant parents become concerned when they hear terms such as “anterior placenta” or “low-lying placenta” during an ultrasound.
In most cases:
- An anterior placenta is a normal finding.
- A low-lying placenta identified at the 20-week morphology scan often resolves naturally.
- Additional scans are commonly performed simply to confirm placental position as pregnancy progresses.
- Most placental variations do not affect your baby’s growth or development. [rcog.org.uk], [ranzcog.edu.au], [rcog.org.uk], [tommys.org]
If your healthcare provider recommends follow-up imaging, it is usually precautionary and helps ensure the safest care for you and your baby. [rcog.org.uk], [seslhd.hea…nsw.gov.au]
Key takeaways
The placenta is a remarkable organ that supports pregnancy by delivering oxygen and nutrients, removing waste products and producing hormones that help sustain fetal development. [ranzcog.edu.au], [rcog.org.uk]
Most placental positions—including an anterior placenta—are normal variations and do not affect pregnancy outcomes. [rcog.org.uk], [ranzcog.edu.au]
If a low-lying placenta is identified during the 20-week morphology scan, it will often move higher as the uterus grows, and follow-up imaging is commonly recommended to confirm its position later in pregnancy. [rcog.org.uk], [pregnancyb…aby.org.au], [seslhd.hea…nsw.gov.au]
Understanding your placenta and the terminology used in ultrasound reports can help you feel more informed, reassured and confident throughout your pregnancy.
References
- Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG). Women’s Health Patient Information Resources. Available at: https://ranzcog.edu.au/womens-health/patient-information/ [ranzcog.edu.au], [ranzcog.edu.au]
- Pregnancy, Birth and Baby. Placenta Praevia. Australian Government service supported by Healthdirect Australia. Available at: https://www.pregnancybirthbaby.org.au/placenta-praevia [pregnancyb…aby.org.au], [healthdirect.gov.au]
- Royal College of Obstetricians and Gynaecologists (RCOG). Placenta Praevia, Placenta Accreta and Vasa Praevia. Available at: https://www.rcog.org.uk [rcog.org.uk], [rcog.org.uk]
- RCOG Green-top Guideline No. 27a. Placenta Praevia and Placenta Accreta: Diagnosis and Management. Available at: https://www.rcog.org.uk [pregnancyb…aby.org.au]
- Cleveland Clinic. Anterior Placenta: What It Means, Diagnosis & Complications. Available at: https://my.clevelandclinic.org [rcog.org.uk]
- Tommy’s. Anterior Placenta. Available at: https://www.tommys.org [ranzcog.edu.au]
- Tommy’s. Low-Lying Placenta (Placenta Praevia). Available at: https://www.tommys.org [rcog.org.uk]
- South Eastern Sydney Local Health District. Placenta Praevia and Low-Lying Placenta Clinical Guidance. Available at: https://www.seslhd.health.nsw.gov.au [seslhd.hea…nsw.gov.au], [seslhd.hea…nsw.gov.au]