I am uncertain in your definition of "misdelivery." If it is about prematurity, then speaking of the reasons amounts to writing a whole book. Your inquiry touches one of the broadest concepts in obstetrics and perinatology. A short answer would be this:
PREMATURE BIRTH is a birth between the 22th and 37th gestation weeks (regardless of birth weight).
LOW BIRTH WEIGHT is the fetal weight between 500 an 2500 grams (regardless the gestation weeks). These babies are named as small for gestational age (SGA) neonates.
INTRAUTERINE GROWTH RESTRICTION (IUGR) is the weight less than the 10% for the gestational age at birth. The IUGR is subdivided into:
- symmetric (the worse case, as the factors are inherent to fetus or have affected the fetus from early stages of pregnancy, and those factors include chromosomal, genetic, or infectious teratogens);
- asymmetric (a better case, as the factors have affected the fetus on later stages, after the 57th day of pregnancy).
An infant, therefore, may be one, two, or three of the above. In order to differentiate between, several indices are used: height, head circumference/abdominal circumference, femur length/abdominal circumference, amniotic fluid scale, etc.
Spontaneous (not induced or augmented) preterm birth accounts for ~ 70% of preterm deliveries. Causes include:
MATERNAL FACTORS - uterine malformation (uterine septum, uterine horn, bicornuate uterus, fibroids, scar, Mullerian duct fusion), deficient placentation (due to endometritis, uterine myoma, uterine scar from the former C-section, placenta previa), incompetent cervix, vertical infections (rubella, syphilis, CMV, toxoplasmosis, HIV, group-B streptococcus, chlamydia), urinary tract infections (mostly bacterial), anemia, smoking, hypertension, preeclampsia, eclampsia, diabetes, serious mental illness, hyperthyroidism, thyroid storm, hyperparathyroidism (in its three expressions), isoimmunization (RH factor, LHA factor), autommune diseases (lupus, Addison's disease, Celiac disease, Sjogren syndrome, multiple sclerosis, etc), poor nutrition, obesity, exposure to the hazards (second hand smoking, vibration, noise, stress, radiation), maternal age < 18 years, poor social support, low education, complicated obstetrical history (prior preterm birth, or second trimester), abruptio placentae or PROM, teratogen medications (beta-mimetics taken for heart diseases, prostaglandins, unnecessary hormonal therapy, lead, diethylstilbestrol, folic acid antagonists, coumadin, lithium, valproic acid, trimethadione, thalidomide, phenytoin, tertacycline, etc ).
FETAL FACTORS - fetal demise or lethal anomalies, uncorrectable fetal distress, aneuplody - trisomy 21 [Down syndrome], trisomy 18 [Edward's syndrome], trisomy 13 [Patau's syndrome]; sex chromosome anomalies - 45X [Turner], 47 XXY [ Klinefelter's]; polyploidy- triploidy 69 XXX, XXY, XYY, or tetraploidy 92XXXY, XXYY; twins, multitons, twin-transfusion syndrome, etc.
BOTH - the IUGR in presence of pulmonary maturity; amniotic fluid volume (polyhydramnios, olygohydramnios), sad fetus syndrome (growing fetus in the presence of trophoblastic diseases).
Treatment depends on the accurate determination of the case. Symptomatic treatment includes tocolysis - if the amnotic fluid is intact, there is no bleeding, the fetus is alive, and mother does not suffer cardiac diseases. Contraindications for tocolysis are: maternal anemia (hematocrit < 34%), occult amnionitis or abruption, underdiagnosed or undetected cardiac disease, prolonged (> 24 hours) infusion of parenteral drugs, concurrent adminsitration of steroids, profuse bleeding, among others. Other treatment methods include: cervical cerclage, antibiotic therapy, immunomodulation.
Given your obstetrical history, the next pregnancy (regardless it is uneventful or eventful) must be delivered by c-section (regardless the fetal weight). A proper investigation after the 22th weeks, at the high risk pregnancy unit (even in asymptomatic pregnancy) would be a wise choice.
This was the shortest answer. Good luck.
Naira R. Matevosyan (Naira Roland Matevosyan), MD, PhD, DSc, JSM
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