Causes of Preterm Birth

By Dr Alan Lindemann

Miscarriage is the loss of a pregnancy before 20 weeks. Losing a pregnancy after 20 weeks is called stillbirth. The cause of a loss of a pregnancy before 12 weeks is probably unavoidable and involves some sort of genetic condition which is incompatible with life.

The term preterm birth is applied to any birth before completing 37 weeks of pregnancy. Many preterm births attributed to unknown causes are often not really unknown. They are simply undiagnosed. No one has looked for the cause. Many times the cause cold be determined if your doctor simply searched for it. If the cause is present but was not looked for, the loss is not inevitable. If the cause can be found and treated, the next pregnancy can have a successful outcome. 

Many Organisms Can Cause Preterm Birth

Your doctor needs to know what organisms to look for and when to look for them to prevent preterm birth caused by various bacteria. For reasons we don’t know, these organisms cause problems for some women and not others. In your first prenatal visit, you doctor could test for the following organisms, but will probably not because the bacteria have not been officially recognized as causes of pregnancy:
• Ureaplasma urealyticum, 
• Bacterial vaginosis, and
• Group B streptococcus.

The Complete Preterm Birth Workup

For patients with a history of preterm birth, more than one loss of a baby in the second trimester, or pregnancy loss of unclear cause, my complete prenatal workup included the following tests for both the patient and her partner. Ideally, this workup should be done before the any pregnancy, not just a pregnancy after you have had a miscarriage or preterm birth: 

• Ureaplasma urealyticum culture,
• Mycoplasma hominis culture. 
• Chlamydia trachomatis, 
• Neisseria gonorrhoeae, 
• Group B streptococcus, 
• Bacterial vaginosis assessment, and 
• Immune studies. 

For me, one of the saddest situations I found with my patients were the ones who came for their first prenatal visit with me and reported serial losses of their babies when the babies were very close to being old enough to survive, those at 21, 22 and, 23 weeks. Their losses had been called unknown because nobody had bothered to look for the organism causing them. The cause was present. It went undiagnosed. When the organism causing the pregnancy loss is found and treated in both partners, the next pregnancy will most likely be more successful. With these organisms tested for, identified, and treated for in both mothers and fathers (yes, fathers can carry the organisms which cause pregnancy loss) those who had lost previous pregnancies could bring home living children.  

I will never forget a couple who came to me for help with their inability to get pregnant. They had had in vitro treatments several times, never resulting in a pregnancy. They taught English is schools in other countries and were heading for a foreign country in three weeks. They said they were leaving in 10 days and “you have one week to solve this problem.” I tested for the common pathogens I knew caused problems in pregnancy. The test for ureaplasma came back positive. This organism can make a woman’s cervical mucous very hostile to sperm (something we now know after 40 years). I treated both the woman and her husband with doxycycline. Six weeks later I received a call from the woman that she was pregnant. Eight months later I received a call that she had delivered a healthy girl with normal weight and normal Apgars.

There is an important lesson here for woman and men suffering from infertility and multiple miscarriages. Causes of pregnancy loss can often be found if they are looked for. Fertility clinics sometimes want to wait until there are two lost pregnancies before working with a patient. No women should have to lose two pregnancies before her a clinic begins looking for the cause. It is important to not overlook the smallest details, the ones that cost almost no money to check on and carry almost no risk compared to the problems and costs that can be associated with multiple laparoscopies and in vitro fertilization.