Preventing Preterm Birth

By Dr Alan Lindemann

The standard answer to what causes preterm birth often is “we don’t know.” Some risk factors may be identified, such as a prior preterm birth, multiple babies, cervical insufficiency, smoking, preeclampsia (which we now know has a paternal, male partner contribution), and certain infections, but in a significant proportion of cases the cause of preterm birth is listed as unknown. 

Many preterm births attributed to unknown causes are really not unknown. Rather, they are simply left undiagnosed. The cause exists; but was simply not identified because there was no attempt to determine the cause. For me, the saddest situation I saw in my clinic were the patients who came in with several losses of babies near the age when they could have survived:  21 weeks, 22 weeks, 23 weeks. They were told the pregnancy losses were unknown. Nobody had bothered looking for the organism which was causing the losses. The cause was present. It was undiagnosed. When the organism was found and treated in both a woman and her partner, the next pregnancy would last beyond the 21 weeks when a baby could survive preterm birth. Some women would even reach full term in their pregnancy. Mothers who had lost three pregnancies would take home living babies.

My clinical experience over forty years, treating a large infertility and high-risk obstetric practice in a community of 80,000 people taught me that many of the cases of preterm birth which were designated to be from unknown causes were not really unknown. The causes simply went undiagnosed. The organisms responsible for the preterm labor were present in the mother and in her partner but no one was looking for them. When the reasons were sought, found, and treated in both partners, the outcomes improved. 

Undiagnosed is not the same situation as unknown. If the cause is present but not looked for, the loss is not inevitable. If the cause can be found, it can be treated. The next pregnancy can have a different outcome. 

Bacterial Causes of Preterm Birth

There are a number of bacterial infections which may not cause problems when a woman is not pregnant, but in some women can cause preterm birth. We don’t know why pregnant women react differently to these infections, but we can check for these organisms and treat for them before they have a chance to cause problems in a pregnancy.

Ureaplasma Urealyticum

Ureaplasma urealyticum is a mycoplasma organism (there are many—some more troublesome than others) that colonizes the urogenital tract of men and women and shows no symptoms in a large percentage of the adult population. The American Academy of Obstetricians and Gynecologists (ACOG) until recently considered ureaplasma so common it was not clinically significant. My observation of patients was that ureaplasma ascending into the amniotic space is not benign. It causes an inflammatory response in the membranes and amniotic fluid that triggers preterm labor often in the second trimester in the window just before your baby reaches the point of being able to survive outside the womb. 

Not all ureaplasma strains cause trouble in all patients. Either a particularly virulent strain or a patient may be unable to contain a colonization of the bacteria that would be a normal colonization in another patient. This is why not every woman with ureaplasma will have a preterm birth. 

Bacterial Vaginosis (BV)

BV is an overgrowth of anaerobic bacteria in the vagina. BV has long been considered a local condition rather than an infection which can travel upward from the vagina to contaminate the amniotic fluids and produce preterm labor and preterm birth. BV has been notoriously difficult to cure. It responds to treatment but returns. We have recently discovered that the male partner is in some way responsible for the recurrence. This is an idea which I have long held and it is now well documented. Women need to be treated much less often if the male consort is also treated. In spite of the connection between female and male partners, there is still a reluctance to call BV an STI, (a sexually transmitted infection)
    
Group B Streptococcus 

Group B Streptococcus is a bacterial organism that colonizes the vagina, perineum and rectum of approximately 10 to 30 percent of pregnant women. ACOG’s current protocol for treating Strep B in pregnancy is to screen for the infection at 35 to 37 weeks of pregnancy and treat the patient with penicillin or ampicillin once the patient is in labor and her water has broken. 

Group B Strep is diagnosable early. It is treatable with inexpensive, widely available antibiotics which are safe in pregnancy. ACOG claims treating early is ineffective because the infection reoccurs. So, retreat the patient and her partner so she can go into labor without the possibility of her baby developing pneumonia (at the time of birth) or meningitis 2 or 3 months later.

The Complete Preterm Birth Workup

For patients with a history of preterm birth, second-trimester loss, or pregnancy loss of unclear cause, my complete workup included the following, for both the patient and her partner, ideally before the next pregnancy: 

    •  Ureaplasma urealyticum culture (must be specifically requested), 
    •  Mycoplasma hominis culture, 
    •  Chlamydia trachomatis, 
    •  Neisseria gonorrhoeae, 
    •  Group B streptococcus, 
    •  Bacterial vaginosis, and
    •  Immune studies. 

This workup can be done in the first prenatal visit.

Other Causes of Preterm Birth Besides Undiagnosed Bacteria

Preeclampsia 

Preeclampsia is both a cause of preterm birth and a reason for medically indicated preterm delivery. The placental vascular disease driving preeclampsia may restrict a baby’s growth and cause fetal distress which requires early delivery. Recognizing early signs of preeclampsia in a first blood pressure elevation and monitoring blood pressure helps prevent preterm birth. 

Systemic Infection

Infection anywhere in the body can trigger preterm labor through the prostaglandin pathway. The uterus responds to systemic inflammation as it responds to local infection. Pneumonia, pyelonephritis, appendicitis, and other systemic infections can initiate contractions in response to local infections. This is why any significant illness during pregnancy warrants prompt evaluation and treatment, not because the illness itself is more dangerous in pregnancy, but because the uterine response to systemic inflammation can be dangerous in pregnancy. 

Late Preterm Birth

A baby born at 35 weeks is not almost term. The phrase late preterm birth is applied to babies born between 34 and 36 weeks and 6 days. These babies can survive being born this early, but these babies still lack some essential development which would have occurred in the womb if they had not been born early. 

Your baby’s brain at 35 weeks weighs approximately two-thirds of what it would weigh if your baby had not been born for another 4 or 5 weeks. The final 5 weeks of brain development include forming myelin sheaths around nerve fibers, the formation of vertical columns of neurons in the brain cortex, and the increasing density of synapses. Without the opportunity to develop this brain growth, late preterm babies have higher rates of learning disabilities, attention difficulties, and developmental delay than term babies. The neonatal intensive care unit can support the baby’s preterm breathing and nutrition, but it cannot replicate the neurological environment of the final weeks in the womb. 

Do seek the cause of any preterm birth so the problem may be addressed in any subsequent pregnancy.