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Placenta previa is a condition in which the placenta covers the cervix (which links the uterus to the vagina) marginally, partially or completely.

Here’s how this occurs: The development of the placenta begins soon after a fertilised egg gets implanted in the uterus. Usually, the blastocyst (the fertilised egg that has already taken the first steps towards becoming an embryo) gets implanted towards the top, side, front or back of the uterus. In one out 200 pregnancies, however, the blastocyst gets implanted so close to the cervix that the placenta ends up covering all or part of the cervix as it develops.

Placenta previa in the early stages of pregnancy may resolve on its own—as the uterus gets bigger to accommodate the growing baby, it may pull the placenta up and away from the cervix by the 20th week of pregnancy. If this doesn’t occur, your doctor may recommend an ultrasound during the 32nd week of pregnancy to monitor the position of the placenta. You may also be advised bed rest or at least less strenuous activity in the latter half of your pregnancy—for some women, this also means no sex during pregnancy.

Placenta previa is associated with a few complications. To begin with, women with a low lying placenta and placenta previa may experience vaginal bleeding; the use of a tampon is not recommended if your bleeding during pregnancy is due to placenta previa.

Placenta previa in the latter half of the pregnancy also increases the risk of heavy bleeding during and after labour—as the cervix effaces (becomes thinner) and dilates (opens up) during labour, it could damage the placenta and severe some of the blood vessels running from the uterus to the placenta. This is considered to be one of the major causes of death during childbirth in developing and poor countries.

Placenta previa also increases the chances of PPROM or preterm premature rupture of membranes, in which a pregnant woman’s water breaks before 37 weeks of gestation: this can increase the chances of premature labour and infections.

Placenta previa is diagnosed through an ultrasound between the 18th week of pregnancy and the 21st week of pregnancy. A low lying placenta doesn’t feel different, though women may be able to tell the difference if they experience bleeding (the blood tends to be bright red). If you are diagnosed with this condition, it is important to stay in touch with your doctor and monitor the condition.

If the condition does not resolve enough in time for the delivery, a C-section (cesarean delivery) has to be performed.

  1. What is the placenta? What does it do?
  2. Types of placenta previa
  3. Placenta previa symptoms
  4. Placenta previa risk factors
  5. Placenta previa diagnosis
  6. Treatment and tips for placenta previa
  7. Placenta previa complications
Doctors for Placenta previa

Before we get into the placement of the placenta, let’s take a minute to look at what a placenta is and what makes it so special. 

  • The placenta is an organ that develops during the first few weeks of pregnancy. On the one hand, the placenta connects the baby to the mother via the umbilical cord. On the other hand, it acts as a barrier between the two, to prevent the transmission of bacterial infections from mom to baby in the womb.
  • The placenta selectively allows the passage of useful things like oxygen, nutrients and antibodies from the mom to the baby—these antibodies give the baby immunity for up to three months after birth.
  • The placenta also produces estrogen and progesterone hormones that are crucial to sustaining the pregnancy.

Placenta and the umbilical cord are sometimes used interchangeably, but they are not the same: whereas the placenta gets the nutrients and oxygen-rich blood from the mom-to-be, the roughly 50 cm-long umbilical cord actually delivers the nutrients to the baby. Similarly, waste from the baby’s body (like carbon dioxide) travels through the umbilical cord to the placenta from where it goes into the expecting mom’s bloodstream to get rid of. (Research has shown that babies pee in the womb from the eighth week of pregnancy, but this pee keeps collecting in the amniotic sac.)

Given the massive role that the placenta plays in supporting the baby and sustaining the pregnancy, any abnormality or problem with the placenta can affect the outcome for mother and child.

Placenta previa occurs in one in 200 cases. In many cases, it resolves on its own. When it doesn’t, it can lead to some symptoms and complications—most significantly, heavy bleeding and premature labour.

The placenta remodels the blood vessels in the expecting mom’s uterus within weeks of implantation—so at any given point of time, the placenta has access to the maternal blood. In placenta previa, the placenta is low-lying or over the cervix. This condition is associated with bleeding during pregnancy, and potentially heavy bleeding during and after delivery.

Depending on how much of the cervix is covered by the placenta, placenta previa is divided into three types:

  • Marginal: If only a small portion of the cervix is covered by the placenta, then this is called marginal placenta previa. If this condition continues till the end of term, then the doctors would decide whether a normal delivery would be safe in your case or not.
  • Partial: A large enough portion of the cervix is covered by the placenta, to present risks of bleeding and require C-section delivery.
  • Complete: The placenta is placed over the cervix in a way that it completely blocks off the birth canal. This is a potentially dangerous situation, as attempting a normal delivery in this case could cause severe bleeding—as the cervix thins out and starts to dilate during labour, it could stretch and break the blood vessels in the placenta and the mom-to-be could bleed to death. This requires a C-section delivery.

A low-lying placenta of placenta previa does not feel different. However, some women may observe bleeding in the second half of their pregnancy—this is not accompanied by pain but some women may experience contractions. (Read more: Contractions during pregnancy)

Though the cause of placenta previa is not known, there are some risk factors associated with the condition. These are:

  • Smoking
  • Being over 35 years old
  • Previous cesarean C-section or scars of previous uterus surgery
  • Placenta previa in a previous pregnancy
  • Twin or multiple pregnancy, or carrying twins or more babies

If placenta previa is diagnosed properly, your doctor can guide you on the safest path for you and your baby. If the baby’s delivered in a hospital where emergency C-section and blood transfusion are both available, the prognosis is also generally good for mom and baby.

In the case of bleeding during pregnancy, an ultrasound may be done to rule out placenta previa. There’s no need to worry if it is indeed placenta previa—it just means you have to take a few extra precautions and scans. In most cases, placenta previa resolves on its own as the expecting mom’s baby bump gets bigger in the second and third trimester of pregnancy.

In case there is no bleeding, placenta previa would be seen in the extremely important Level 2 ultrasound which is done between the 18th week of pregnancy and 21st week of pregnancy—this is also the pregnancy ultrasound that helps to spot “birth defects” like open spina bifida and congenital heart disease, so you should not miss this ultrasound appointment.

If your doctor finds evidence of placenta previa in this ultrasound scan, then he or she may ask you to get more ultrasounds done—especially during the 32nd and 36th week of pregnancy. This will help the doctor determine if the placenta previa has resolved before delivery or not. If it hasn’t, you may have to spend some time in the hospital and a cesarean section will likely be done to deliver your baby.

The doctor may also do a transvaginal ultrasound, MRI scan or transabdominal ultrasound to get a clearer picture of the extent of placenta previa.

There’s no need for any treatment till the 20th week of pregnancy—your doctor may advise that you put your feet up and avoid strenuous activity to reduce the chances of heavy bleeding, though.

If placenta previa does not resolve on its own by the end of week 20, then you may be asked to make some lifestyle changes:

  • Depending on the severity of the case, doctors may advise that you avoid strenuous activities like exercise or go on complete bed rest.
  • If the placenta previa doesn’t resolve towards the end of your term, you may have to spend a few weeks in the hospital to make sure there are provisions for blood transfusion, in case you need it.
  • Your doctor may also minimise vaginal examinations if he or she suspects placenta previa.
  • If your doctor feels you may not be able to complete 37 weeks of gestation, then based on your reports and medical history, he or she may schedule a C-section before that. If this happens, your doctor may give you corticosteroids to help your baby’s lungs develop faster.
  • Placenta previa linked bleeding during pregnancy may trigger preterm premature rupture of membrane—a type of early water breaking. If your water does break early, an emergency C-section would have to be done. A blood transfusion may also be necessary, depending on how much blood you lose as the cervix dilates during labour and afterwards (in afterbirth where women have uterine contractions to expel the placenta after delivery).

If you experience bleeding because of placenta previa, you should not use tampons.

Normally, sex during pregnancy is safe as well as enjoyable. If you are diagnosed with placenta previa, however, your doctor may ask you to abstain from having sex and masturbating.

Data show that nearly nine out of 10 cases of placenta previa resolve on their own by the 20th week of pregnancy. In these cases, placenta previa is usually nothing to worry about. That said, there are also some complications associated with placenta previa if it does not resolve by week 20. They are:

  • Breech position and breech baby: A breech baby has his or her feet towards the cervix. Normal delivery for a breech baby is anyway risky, and will depend on the discretion of the doctor.
  • Placenta accreta: In addition to being over the cervix, the placenta becomes deeply embedded in the uterus (much more than normal), which can increase the chances of heavy bleeding. In the case of placenta accreta, the doctor may have to perform Cesarean hysterectomy (remove the uterus during the cesarean operation) and hypogastric artery ligation (tying off the internal iliac or hypogastric artery that supplies blood to the pelvic region) to save the patient’s life.
  • PPROM: PPROM is when a pregnant woman’s water breaks before 37 weeks of pregnancy. This can necessitate an emergency C-section. In women with placenta previa, any effacing and dilation in the cervix (during the first phase of labour, the cervix dilates to 10 centimeters) can cause heavy bleeding.
  • Heavy bleeding: Placenta previa presents with risk of bleeding. While a little bit of bleeding can be managed, heavy bleeding can be a cause for concern. In some cases, the doctor may schedule a Cesarean delivery before the 37th week of pregnancy to reduce this risk.
  • Premature labour
Dr. Vrinda Khemani

Dr. Vrinda Khemani

Obstetrics & Gynaecology
6 Years of Experience

Dr Megha Apsingekar

Dr Megha Apsingekar

Obstetrics & Gynaecology
4 Years of Experience

Dr. Dyuti Navadia

Dr. Dyuti Navadia

Obstetrics & Gynaecology
1 Years of Experience

Dr. Sheetal Aggarwal

Dr. Sheetal Aggarwal

Obstetrics & Gynaecology
15 Years of Experience

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