Placenta previa is a pregnancy condition in which the placenta partially or completely covers the cervical opening (cervical os). For women pregnant after 35, understanding placenta previa—its risk factors, how it is identified, and how it is managed—can help reduce anxiety and support clearer conversations with an obstetric team. While the condition requires careful monitoring and often changes delivery planning, it is also a well-understood condition with established management protocols.
According to the American College of Obstetricians and Gynecologists (ACOG), placenta previa occurs in approximately 1 in 200 pregnancies at term. It is more common in the second trimester, when many ultrasounds first detect a low-lying placenta, but most cases resolve as the uterus grows and the placenta effectively moves upward away from the cervix. Persistent previa at term is less common.
Risk Factors for Placenta Previa After 35
Several factors are associated with an increased likelihood of placenta previa, and women over 35 may have a higher baseline risk due to the accumulation of some of these factors over time.
Previous Uterine Surgery
Prior caesarean section is one of the most significant risk factors for placenta previa in subsequent pregnancies. Uterine scarring from previous surgeries—including caesarean delivery, myomectomy (fibroid removal), or other uterine procedures—may affect how the placenta implants. Women over 35 who have had a previous caesarean are at modestly higher risk in subsequent pregnancies.
Multiple Pregnancy and Assisted Conception
Twin and higher-order pregnancies are associated with increased placenta previa risk, as are pregnancies conceived through IVF in some studies—though the mechanisms are not fully established. Since multiple pregnancies and IVF use are more common after 35, these factors are worth being aware of in the context of prenatal monitoring. Our overview of prenatal testing after 35 covers how these factors are monitored across the pregnancy.
How Placenta Previa Is Diagnosed
Placenta previa is typically identified on routine prenatal ultrasound. A low-lying placenta or suspected previa in the second trimester is common and usually monitored with a follow-up ultrasound at around 32–36 weeks, as the majority of cases resolve as the uterus grows. If previa persists at the late-pregnancy ultrasound, delivery planning will be adjusted accordingly.
Transvaginal ultrasound is the most accurate method for assessing placental position relative to the cervix and is safe to perform even with a low-lying placenta. Women should not avoid this form of ultrasound if it is recommended by their healthcare provider, as it provides important clinical information.
Symptoms and When to Seek Urgent Assessment
The hallmark symptom of placenta previa is painless vaginal bleeding, typically bright red, occurring in the second or third trimester. This bleeding results from disruption to the placenta near the cervical opening. Any vaginal bleeding during pregnancy—whether or not previa has been identified—warrants prompt assessment by a healthcare provider. Women with known placenta previa should be aware of this symptom and have clear guidance from their obstetric team about when to seek urgent care.
Managing Placenta Previa
Management of placenta previa depends on its severity, gestational age, and whether bleeding has occurred. Asymptomatic previa identified early in pregnancy is typically monitored with repeat ultrasound rather than immediate intervention. Women with persistent previa in the third trimester will generally be advised to avoid penetrative intercourse and may be counselled to limit strenuous activity, though specific restrictions depend on individual circumstances and provider guidance.
Delivery by caesarean section is recommended for women with placenta previa that persists at term, as vaginal delivery would risk severe haemorrhage. The timing of planned caesarean—typically between 36 and 37 weeks for uncomplicated cases—is determined based on individual assessment of risks and benefits. Women with previa who experience significant bleeding earlier in pregnancy may require hospitalisation and earlier delivery depending on the clinical situation.
Frequently Asked Questions
Will a low-lying placenta at 20 weeks become previa?
Not usually. The majority of low-lying placentas identified at the mid-pregnancy anatomy scan resolve by the third trimester as the uterus expands and the lower uterine segment develops. A follow-up ultrasound at 32–36 weeks is standard practice to confirm whether the placenta has moved away from the cervix. Only a minority of cases persist as true previa at term.
Can I have a vaginal birth if I have placenta previa?
Vaginal delivery is not considered safe for confirmed placenta previa at term because of the risk of severe maternal haemorrhage. Caesarean delivery is the recommended mode of birth. If you have concerns about this, discussing them openly with your obstetric team allows for informed planning and preparation for what to expect.
Does placenta previa affect the baby?
Placenta previa itself does not directly harm the baby in most cases, but significant maternal bleeding associated with previa can affect placental function and foetal wellbeing. Preterm delivery—either due to previa-related bleeding or planned early caesarean—is the most common way the baby may be affected. Foetal monitoring is part of management for women with previa who experience bleeding.
Is placenta previa more common after 35?
Research suggests a modest association between maternal age and placenta previa risk, though the absolute risk even in older mothers remains low. Prior caesarean delivery—which is more common in women over 35 who have had previous pregnancies—is a stronger risk factor than age alone. Routine prenatal ultrasound effectively identifies the condition when it does occur.
Key Takeaways
- Placenta previa occurs when the placenta covers the cervical opening; most low-lying placentas identified at 20 weeks resolve by the third trimester.
- Risk factors include previous uterine surgery (especially caesarean), multiple pregnancy, and IVF conception—all more common after 35.
- Painless bright-red vaginal bleeding in the second or third trimester is the key symptom and always warrants prompt medical assessment.
- Persistent previa at term requires caesarean delivery; timing and management are planned in detail with the obstetric team.
- Routine prenatal ultrasound effectively identifies placenta previa, and management protocols are well established.
Medical Disclaimer
This content is for informational purposes only and does not constitute medical advice. Individual health situations vary significantly. Always consult a qualified healthcare provider before making decisions related to your health, fertility, or pregnancy.
About the Author
Emily Carter is a women’s health writer focused on fertility, pregnancy after 35, and sleep changes in midlife. She writes research-informed, non-alarmist content to help women navigate reproductive and hormonal transitions with clarity and confidence.