What is pre-term birth?
It’s estimated that today more than 1,400 babies in the United States will be born prematurely or pre-term1 . That’s one in eight babies and many of them will be to small or two sick to go home. Instead, they will face weeks – or possibly months – in the Newborn Intensive Care Unit ( NICU ). They will face an increased risk of serious complications and, possibly, even death; however, most, eventually, will go home.
The question is what does the future hold for these babies? While many grow up healthy and thrive, others aren’t always so lucky. Even the best of care cannot always spare a premature baby from lasting disabilities such as cerebral palsy, mental retardation and learning problems, chronic lung disease, vision and hearing problems. Doctors estimate that one-half of all neurological disabilities in children are related to premature birth.
What causes pre-term birth? In humans, whereas the usual definition of pre-term birth is a birth occurring before thirty-seven (37) weeks gestation2 a “premature” infant is one that has yet to reach the level of fetal development that generally allows life outside of the womb. In a normal human fetus, several organ systems mature between 34 and 37 weeks, and the fetus reaches adequate maturity by the end of this period. One of the primary organs that is greatly affected by pre-term birth is the lungs as they are one of the last organs to develop in the womb. Because of this, there is a significant overlap between pre-term birth and prematurity, pre-term babies are premature and term babies are mature.
Since the cause of labor remains elusive, the exact cause of pre-term birth also remains unsolved. Labor is a complex process involving many factors. To date, four factors have been identified which can result in pre-term birth:
Infection / Inflammation – Studies have shown that premature labor is often triggered by the body’s natural immune response to certain bacterial infections, such as those involving the genital and urinary tracts as well as the fetal membrane(s). Even infection far away from the reproductive organs, such as periodontal disease, may contribute to pre-term delivery.
Maternal or fetal stress – Chronic psychological stress involving the mother or physical stress (such as insufficient blood flood from the placenta) in the fetus appears to result in production of a stress-related hormone called corticotropin-releasing hormone (CRH). CRH may stimulate production of a cascade of other hormones that trigger uterine contractions and pre-term delivery. Bleeding – The uterus may bleed because of problems such as placenta abruption (where the placenta peels away, partially or almost completely, from the uterine wall prior to delivery).
Grade 0 Asymptomatic and only diagnosed through post-partum examination of the placenta. Grade 1 The mother may have vaginal bleeding with mild uterine tenderness or tetany3, but there is no distress of the mother or fetus. Grade 2 The mother is symptomatic but not in shock. There is some evidence of fetal distress that can be detected with fetal heart rate monitoring. Grade 3
Severe bleeding (which may be occult4) leads to maternal shock and fetal death.
This bleeding triggers the release of various proteins involved in the clotting process which appear to also stimulate uterine contractions.
Stretching – The uterus may become over-stretched due to the presence of two or more babies, excessive amounts of amniotic fluid, and uterine or placental abnormalities that cause the release of chemicals that stimulate uterine contractions.
Who is at risk for early delivery?
Generally, it is very difficult to predict which women will deliver prematurely. Currently, tests are not considered helpful in identifying low-risk women. However, there are two tests that are useful in determining which high-risk or women having contractions are unlikely to deliver in the next two weeks. These tests can both relieve worries and spare unnecessary treatments.
Cervical length – The length of a woman’s cervix is measured using vaginal ultrasound. Women with a shorter-than-average cervix as well as those whose cervix shortens on subsequent exams are at increased risk for pre-term delivery.
Fetal fibronectin – Fibronectin is a biological glue that helps attach the fetal sac to the uterine lining. It is normally present in vaginal secretions up to twenty-two (22) weeks and then not again until one (1) week to three (3) weeks before delivery. Doctors can take a swab sample of the vaginal secretions between the 22nd and 34th weeks. If the fibronectin is present when the swab is taken, the mother has an increased risk of pre-term labor. This test has proven moderately successful in predicting mothers who willnot deliver pre-term. In certain cases the test for the presence of fibronectin is combined with measurements of the cervix to provide increased accuracy.
What are the signs and symptoms of pre-term delivery?
The symptoms of imminent spontaneous pre-term birth are also the signs of premature labor; this includes four (4) – or more – uterine contractions in one hour before 37 weeks’ gestation. In contrast to false labor, true labor is accompanied by cervical dilation and effacement5 . Additionally, during the third trimester of pregnancy, there can also be vaginal bleeding, heavy pressure in the pelvis, and abdominal or back pain. In some cases, the cervix will dilate prematurely without the usually pain or perceived contractions resulting in the mother not having warning signs until very late in the birthing process.
Is it possible to prevent pre-term birth ?
Historically efforts have primarily been aimed at improving survival and health of preterm infants (tertiary prevention ). Such efforts, however, have not reduced the occurrence of pre-term birth. Increasingly primary interventions that are directed at all women, as well as secondary intervention that reduce existing risks are seen as measures that need to be developed and implemented to prevent the health problems of premature infants and children6 .
Preconceptional – Raising both public and professional awareness regarding the scope of the problem and its significance as a major contributor to infant mortality is a beginning step to reduce an avoidable risk factor. Among these is the need to reduce repeated uterine instrumentation (IE: repeated surgical abortions) as well as avoiding risky choices in infertility treatments. In addition, many countries have established specific programs to protect women from hazardous and night shift work as well as providing them with time for prenatal doctor visits and paid pregnancy leave. Also the avoidance of weight extremes and good nutritional support have also found to be important.
During pregnancy – Interventions which should have been initiated prior to pregnancy, can still be instituted during pregnancy including nutritional adjustments, use of vitamin supplements and smoking cessation. Differing strategies are employed in the administration of both prenatal care, therefore, additional studies are needed to determine if the focus should be more on screening for high risk women, or increased support for low-risk women or if, possibly, these approaches should be merged. Another area that warrants additional study involves periodontal care. The reason being is, although periodontal infection has been linked with pre-term birth, randomized trials have not shown that periodontal care during pregnancy reduces this risk.
What is the prognosis for babies born pre-term?
Most children, even if born very pre-term, adjust very well during childhood and adolescence7. As the survival rate has improved, the focus of interventions directed at the newborn has shifted to reduction of long-term disabilities – particularly brain injury. History has shown that some of the complications associated with prematurity may not become apparent until years after the birth. A long-term study has shown that the risks of medical and social disabilities extended into adulthood and are higher with decreasing gestational age at birth. These disabilities include: cerebral palsy, mental retardation, disorders involving psychological development, behavior, and emotion, vision, hearing, and epilepsy. Babies born prematurely may also be more susceptible to developing depression during their teenage years8. In addition, throughout their life, they are more likely to services provided by physical therapists, occupational therapists, or speech therapists.
© November, 2010
1Source: March of Dimes ( www.marchofdimes.com )
2Steer, P. (2005) “The epidemiology of preterm labor“, British Journal of Obstetrics & Gynecology, pp 1-3
3Tetany is a condition resulting from a severe degree of hypocalcemia – literally, very low calcium levels in the blood.
( http://www.medterms.com/script/main/art.asp?articlekey=13312 )
4Occult bleeding is defined as bleeding that occurs in such a small quantity, that it can only be detected by chemical test or by microscopic or spectroscopic examination.
5Effacement is the process by which the cervix prepares for delivery of a baby by shortening, softening, and becoming thinner.
6Iams, JD; Romero, R; et. al. (2008) “Primary, secondary and tertiary interventions to reduce the morbidity and mortality of preterm birth” The Lancet, pp 164 – 175
7Saigal, S; Doyle, LW (2008) “An overview of mortality and sequelae of preterm birth from infancy to adulthood” The Lancet, pp 261 – 269
8Moster, D; Lie, R.T.; Markestad, T (2008) “Long-term medical and social consequences of preterm birth” New England Journal of Medicine pp 262 – 273