Causes of preterm birth

Some causes of preterm birth

Although the cause is often unknown, a variety of factors play a role in preterm birth:

• Certain genital tract infections, such as chlamydia, bacterial vaginosis (BV), and trichomoniasis, are associated with preterm delivery.

Substances produced by bacteria can weaken the membranes around the amniotic sac and cause it to rupture early. Even when the membranes remain intact, bacteria can cause preterm labor if they get into the amniotic fluid or sac.

You may have been checked for chlamydia and gonorrhea at your first prenatal visit, and you would have been treated immediately if you'd tested positive for either of these sexually transmitted infections.

If you've had a previous preterm birth, you may also have been screened for bacterial vaginosis. Although some studies show that treating BV in the second and third trimesters reduces the risk of preterm labor in women with a history of preterm birth, other research has found that it makes no difference. So experts don't agree on whether it's worthwhile to test pregnant women who don't have symptoms. (If you have symptoms of bacterial vaginosis, you'll be tested and treated with antibiotics, if needed.)

You probably won't be tested for trichomoniasis unless you have symptoms. Some research suggests that treating women for trichomoniasis during pregnancy actually increases the risk of preterm birth.

• Having a problem with the placenta, such as placenta previa or placental abruption.

• Having structural abnormalities of the uterus or cervix, such as a cervix that's shorter than 25 millimeters and that effaces or dilates without contractions (cervical insufficiency).

• Having an excessively large uterus, which is often the case when you're pregnant with multiples or have too much amniotic fluid.

• Certain chronic maternal illnesses may be related to preterm labor, such as diabetes, sickle cell anemia, severe asthma, lupus, inflammatory bowel disease, and chronic active hepatitis. Other conditions to watch for include non-uterine infections, such as a kidney infection or pneumonia; abdominal surgery, such as having your appendix taken out; trauma to the abdomen; and periodontitis (a gum infection that goes into the bone and other tissues that support your teeth).

Preeclampsia

Preeclampsia is a disorder that occurs only during pregnancy and the postpartum period and affects both the mother and the unborn baby. Affecting at least 5-8% of all pregnancies, it is a rapidly progressive condition characterized by high blood pressure and the presence of protein in the urine. Swelling, sudden weight gain, headaches and changes in vision are important symptoms; however, some women with rapidly advancing disease report few symptoms.

Typically, preeclampsia occurs after 20 weeks gestation (in the late 2nd or 3rd trimesters or middle to late pregnancy), though it can occur earlier. Proper prenatal care is essential to diagnose and manage preeclampsia. Preeclampsia, Pregnancy Induced Hypertension (PIH) and toxemia are closely related conditions. HELLP Syndrome and eclampsia are other manifestations of the same syndrome. It is important to note that research shows that more women die from preeclampsia than eclampsia and one is not necessarily more serious than the other.

Preeclampsia and other hypertensive disorders of pregnancy are a leading global cause of maternal and infant illness and death. By conservative estimates, these disorders are responsible for 76,000 deaths each year.