Placenta Previa
A growing foetus requires oxygen, glucose, amino acids and other nutrients to grow. The waste products of the foetus also need to be expelled. These functions are carried out by the placenta. Placenta is an oval fleshy organ which develops soon after implantation and is fully functional by six –eight weeks of pregnancy. It is usually attached to the back wall of the uterus in its upper part known as fundus. But rarely may it be located in the lower part of the uterus, thus fully or partially covering the cervix. This condition is known as placenta previa.
Placenta previa is of three types:
- Complete placenta previa: The placenta is located completely in the lower segment and covers the cervix completely.
- Partial placenta previa: The placenta partially covers the cervix.
- Marginal placenta previa: the placenta just encroaches upon the cervix.
The main danger of placenta previa is its ability to cause torrential bleeding around or after labour. The bleeding may be so profuse to cause shock and death in the mother. Around the time of labour, the cervix starts dilating and this may lead to separation of the placenta, leading to painless profuse vaginal bleeding. The bleeding will stop but commonly recurs days to weeks later.
During the early weeks of pregnancy, the placenta is usually located within the lower segment of the uterus. But as the pregnancy progresses, the placenta climbs up to reach its normal position. However in some women it may remain in the lower segment of the uterus. This is called as low lying placenta and is not worrisome except for a slightly increased risk of excess bleeding post delivery.
The following conditions predispose to placenta previa:
- Scars in the lining of the uterus (endometrium)
- A large placenta, such as with a multiple pregnancy
- An abnormally shaped uterus
- Have already delivered at least one baby
- Had a previous C-section
- Had placenta previa with a previous pregnancy
- Are age 35 or older
- Are Asian
- Smoke
- Are carrying twins, triplets or other multiples
- Have had a previous uterine surgery, such as myomectomy to remove uterine fibroids or dilation and curettage (D and C) to scrape the uterine lining
Placenta previa is commonly diagnosed on ultra sound or after an episode of painless fresh vaginal bleeding toward the end of second trimester and third trimesters. Once it is diagnosed your doctor will monitor you condition very carefully. You can help your doctor by informing him about any relevant conditions you suffer from. Be accurate about the date of your last period. Give detailed information (as much as you can) about D&C or surgery on uterus. When you do go for an appointment with the doctor take a friend or family member with you to provide support. Also ask about any pregnancy restrictions and make a note of the questions you would like to ask your doctor.
Placenta previa has three major complications. Bleeding, premature labour and placenta accreta. The placental separation which occurs in placenta previa in the second and third trimesters can induce contractions and lead to premature labour. Placenta acreta is a condition wherein the placenta implants deep in the muscular layer of the uterus and does not spontaneously separate after delivery.
There are two further conditions which are often clubbed with placenta previa: Vasa previa and placental abruption. The umbilical cord normally originates from the centre of the placenta, but sometime it develops in such a way that some of the blood vessels remain unprotected. If these rupture it can cause fatal bleeding in the baby. Placental abruption is discussed in a different article.
The treatment of placenta previa is dictated by the following factors:
- The amount of vaginal bleeding
- Whether the bleeding has stopped
- Your baby's gestational age
- Your health
- Your baby's health
- The position of the placenta and the baby
If you have little vaginal bleeding which stops spontaneously and you have a marginal placenta previa, then your doctor will advise you bed rest. You should sit and stand only when it is absolutely necessary. Sex and vaginal examinations are a strict no-no. You should also avoid all forms of physical activity and exercise. Do consult with your doctor about any further do’s and don’ts. If the placenta is not covering the cervix, you may be allowed to proceed for a normal delivery, but you must remain mentally prepared for C section.
Heavy bleeding will require blood transfusions to replace the lost blood and also medicines to arrest contractions if any. If the baby is more than 36 weeks of age then it can be safely delivered out, but if the maturity of the baby is not sufficient then you may be given steroid injections to help speed up the maturation of the baby’s lungs. For bleeding which is not controlled emergency C section irrespective of the age of the foetus is mandatory to save the mother. But with the technology and medical care available today even babies born at 22 -24 weeks usually survive.
Although excessive bleeding may not be any woman’s ideal of pregnancy, you must remember that most women who have placenta previa go on to deliver healthy babies.