Zykova I.N. neonatologist

Why does prematurely delivery exist?


The cause of preterm birth is in many situations elusive and unknown; many factors appear to be associated with the development of preterm birth, making the reduction of preterm birth a challenging proposition. In fact, the cause of 50% of preterm births is never determined.
Significant progress has been made in the care of premature infants, but not in reducing the prevalence of preterm birth.

Four different pathways have been identified that can result in preterm birth and have considerable evidence: precocious fetal endocrine activation, uterine overdistension (placental abruption), decidual bleeding, and intrauterine inflammation/infection.


Activation of one or more of these pathways may happen gradually over weeks, even months. From a practical point a number of factors have been identified that are associated with preterm birth; however, an association does not establish causality.

Infections play a major role in the genesis of preterm birth and may account for 25–40% of events. The frequency of infection in preterm birth is inversely related to the gestational age.



Endotoxins released by microorganisms and cytokines stimulate deciduas responses including the release of prostaglandins which may stimulate uterine contractions. Further the decidual response may include release of matrix-degrading enzymes that weaken fetal membranes leading to premature rupture.


It has been reported that asymptomatic colonization of the decidua occurs in up to 70% of women at term using a DNA probe suggesting that the presence of micro-organism alone may be insufficient to initiate the infectious response.

Typical organisms identified in the uterus before rupture of the membranes are genital Mycoplasma spp and specifically Ureaplasma urealyticum. Microorganisms may reach the decidua in a number of ways, ascending, hematogeneous, iatrogenic by a procedure, or retrograde through the fallopian tubes. From the deciduas they may reach the space between the amnion and chorion, the amniotic fluid, and finally the fetus.


A chorioamnionitis also may lead to sepsis of the mother.

Fetal infection not only is linked to preterm birth but to significant long-term handicap including cerebral palsy.


A number of maternal bacterial infections are associated with preterm birth including pyelonephritis, asymptomatic bacteriuria, pneumonia, and appendicitis. Also periodontal disease has been shown repeatedly to be linked to preterm birth. It is opined that bacterial vaginosis before or during pregnancy may affect the decidual inflammatory response that leads to preterm birth.

In contrast, viral infections, unless accompanied by a significant febrile response, are considered not to be a major factor in relation to preterm birth.


Preterm labor and birth can happen to any pregnant woman. But it happens more often to some women than to others. Researchers continue to study preterm labor and birth. They have identified some risk factors, but still cannot predict which women will give birth too early.

Having a risk factor does not mean a woman will have preterm labor or preterm birth. Three groups of women are at greatest risk of preterm labor and birth:
  • Women who have had a previous preterm birth. 
  • Women who are pregnant with twins, triplets or more. 
  • Women with certain uterine or cervical abnormalities.
  •  If a woman has any of these three risk factors, it's especially important for her to know the signs and symptoms of preterm labor and what to do if they occur. 
Some studies have found that certain lifestyle factors may put a woman at greater risk of preterm labor. These factors include:
  •  Late or no prenatal care 
  • Smoking 
  • Drinking alcohol 
  • Using illegal drugs 
  • Exposure to the medication DES 
  • Domestic violence, including physical, sexual or emotional abuse 
  • Lack of social support 
  • Extremely high levels of stress 
  • Long working hours with long periods of standing 
  • Exposure to certain environmental pollutants. 

Certain medical conditions during pregnancy may increase the likelihood that a woman will have preterm labor. These conditions include:

  • Diabetes Infections (urinary, vaginal, sexually transmitted; possibly others) 
  • High blood pressure and preeclampsia 
  • Clotting disorders (thrombophilia) 
  • Bleeding from the vagina 
  • Certain birth defects in the baby 
  • Being pregnant with a single fetus after in vitro fertilization (IVF) 
  • Being underweight before pregnancy 
  • Obesity 
  • Short time period between pregnancies (less than 6 to 9 months between birth and the beginning of the next pregnancy). 

Medical researchers also have identified certain groups of women who are at increased risk of having a premature baby. These groups include:

  • African-American women 
  • Women younger than 17 and older than 35 
  • Women who have a low income