Abortion

Chapter 26. ABORTION


Sept. 25, 1997 1st year resident S.M. Choi. M.D.


I. Overview.

A. Prediction of success and failure in human reproduction


  • Figure 26-1


B. Life span of spermatozoa and ova


  • Life span of liberated germ cells, both spermatozoa and ova, is short
  • Few spermatozoa are capable of fertilization after more than 24hours optimum time for ovum fertilization is substantially shorter, perhaps no more than 1 to 2hours
  • As the liberated germ cells age, the likelihood of formation of an abnormal zygote increases


C. Female fertility inefficiency



  • Attributable to


    • Lack of ovum availability due to anovulation and failure of ova to enter the
      fallopian tube
    • Nonfertilizability of the ovum



  • (1) Ovum availability



    • Anovulation cycle - occur as often as once a year or about once in 13 cycles
    • Luteinized follicle or 'trapped ovum'



  • (2) Fertilizable ova


D. Fecundability



  • Fecundability: likelihood of pregnancy success (live-born infants) per ovarian cycle


  • Evaluate the number of live-born infants that can be expected per ovarian cycles in
    young healthy women desirous of pregnancy

    -> results are expressed as the fecundability rate


  • Natural fecundability in a population of young, healthy, fertile women desirous of
    pregnancy (28 to 30 %) is about half the theoretical maximum fecundability in
    similar women if spermatozoa were not limiting


E. Source of pregnancy losses




  1. Late pregnancy wastage: perinatal mortality - 1%
  2. Early clinical pregnancy wastage: spontaneous first trimester abortion - 10%
  3. Early preclinical loss of conceptus



    • Preimplantation - one of the limiting steps in the success of fertility is the quality
      of the fertilized ovum

    • Early postimplantation (preclinical) embryonic loss


      • Occult pregnancy
      • Evaluated early pregnancy wastage by monitoring the level of chorionic
        gonadotropin in blood or urine of women during the luteal phase


F. Clinical pregnancy




  • Of 1000 cycles in young, healthy, fertile women, 673 clinically discernible
    pregnancies are predicted with an incidence of spontaneous clinical abortion of
    10% and a perinatal mortality of 1%




II. SPONTANEOUS ABORTION



A. Definition




  • Termination of pregnancy by any means before the fetus is sufficiently developed to
    survive
  • Termination of pregnancy before 20weeeks based upon the date of the first day of
    the LMP
  • Delivery of a fetus- neonate that weighs less than 500g, in some European countries,
    this definition is less than 1000g


B. Pathology



  1. Hemorrhage into the decidua basalis and necrotic changes in the tissue adjacent to
    the bleeding
  2. Ovum becomes detached and stimulates uterine contraction
  3. Fluid is commonly found surrounding a small macerated fetus or may be no visible
    fetus in the sac
  4. Blood or carneous mole - ovum is surrounded by a capsule of clotted blood
  5. Fetal maceration - bone of the skull collapse and the abdomen becomes distended
    with blood stained fluid
  6. Fetus compressus
  7. Fetus papyraceous


C. Resumption of ovulation




  • Ovulation may resume as early as 2 weeks after an abortion - effective contraception
    be initiated soon after abortion


D. Etiology of spontaneous abortion



  • More than 80 percent of abortions occur in the first 12 weeks
  • Chromosomal anomalies
  • Parity as well as with maternal and paternal age
  • Woman conceives within 3 months of a term birth


1. Fetal factors

1) Abnormal zygote development



  • Most common morphological finding in early spontaneous abortions is an
    abnormality of developments of the zygote, embryo, early fetus, or at times the
    placenta

2) Aneuploid abortion



  • About 50 to 60% of early spontaneous abortions are a/w a chromosomal anomaly
    of the conceptus
  • 1/4 of chromosomal abnormalities were due to maternal gametogenesis errors and
    5% were due to paternal gametogenesis errors


      a. Autosomal trisomy

      b. Monosomy X (45,X)

      c. Triploidy

      d. Tetraploid abortuses

      e. Chromosomal structural abnormalities

      f. Autosomal monosomy

      g. Sex chromosomal polysomy


3) Euploid abortion
>


  • 3/4 of aneuploid abortions were before 8weeks, while euploid abortions peaked at
    about 13weeks
  • Increases dramatically after the maternal age of 35 years
  • Reasons for euploid abortions



    • Genetic abnormality such as an isolated mutation or polygenic factors
    • Various maternal factors
    • Some paternal factors


2. Maternal factors

1) Infections :



    Brucella abortus,Campylobacter fetus,Toxoplasma gondii, Herpes simplex,
    maternal HIV-1 antibody, maternal syphilis seroreactivity vaginal colonization
    with group B streptococcus. Mycoplasma horminis, Ureaplasma urealyticum


2) Chronic debilitating disease



  • Tuberculosis or carcinomatosis have seldom caused abortions
  • Hypertension is seldom associated with abortion before 20 weeks, but rather may
    lead to fetal death and preterm delivery
  • Celiac sprue cause both male and female infertility and recurrent abortion


3) Endocrinologic abnormalities


  • Hypothyroidism - thyroid autoantibodies
  • DM - lack of glucose control resulted in a marked increase in the abortion rate
  • Progesterone deficiencies



    • Luteal phase defects : diagnosis by midluteal progesterone peak of less than 9 ng/mL or an endometrial biopsy 3 days or more out of synchrony with menstrual dates during two separate cycles


4) Nutrition



3. Drug use and environmental factors



  • Tobacco , alcohol, caffeine, radiation, contraceptives, environmental toxins
  • Anesthetic gas, nitrous oxide
  • Arsenic, lead, formaldehyde, benzene, ethylene oxide may cause abortion
  • Video display terminal exposure to magnetic field , shortwaves, ultrasounds (do
    not increase the risk)


4. Immunologic factors


1) Autoimmune factors


  • Most significant antibodies have specificity against negatively charged
    phospholipids
  • Most commonly detected by testing for lupus anticoagulant & anticardiolipin
    antibody
  • Lupus anticoagulant



    • immunoglobulin (IgG, IgM, or both)
    • interfere with one or more of the phospolipid dependent tests of in vitro
      coagulation



  • Antiphospholipid antibodies


    • acquired antibodies targeted against a phospholipid
    • IgG, IgA, IgM isotope
    • mechanism of pregnancy loss : placental thrombosis and infarction


Fig. 26.5




  • 3 Potential mechanisms



    • Endothelial cell normally convert plasma membrane arachidonic acid into
      prostacyclins, which released into the circulation and prevents platelet
      aggregation

      Antiphospholipid antibody may predispose to thrombosis by inhibiting endothelial cell from producing prostacyclins

    • Platelet normally convert plasma membrane arachidonic acid into
      thromboxane which is released and induce platelet aggregation.

      Antiphospholipid antibody may increase thrombosis by enhancing
      thromboxane release

    • During clotting, thrombin forms a complex on the surface of endothelial
      cells with its receptor, thrombomodulin.

      -> thrombin/ thrombomodulin complex is enzymetically active and can
      activate circulating protein C.

      -> activated protein C binds with protein S on the surface of endothelial
      cells and platelet.

      -> protein C / protein S complex degrades circulating activated components
      of the clotting cascades, factor Va and Vllla.


  • Tx. for APA syndrome #

    : low dose aspirin, prednisone, heparin, intravenous immunoglobulin


2) Alloimmune factors



  • A number of women with recurrent pregnancy loss have been diagnosed as
    having an alloimmune cause
  • They have received a variety of therapies targeted at stimulating maternal
    immune tolerance of fetal material
  • Dx of an alloimmune factor has centered on several tests



    • Maternal and paternal HLA comparison
    • Assessment of maternal serum for the presence of cytotoxic antibodies to paternal leukocyte
    • Maternal serum testing for blocking factors for maternal - paternal mixed lymphocyte reaction


5. Aging gametes


  • Aging of the gametes within the female genital tract before fertilization increased
    the chance of abortion


6. Laparotomy




  • No evidence that surgery performed during early pregnancy cause increased
    abortions
  • Peritonitis increase the likelihood of abortion


7. Uterine defect




  • Aquired uterine defect: uterine leiomyomas, uterine synechiae
  • Developmental uterine defect



    • abnormal mullerian duct formation or fusion: may occur spontaneously or be
      induced by in utero exposure to DES

8. Incompetent cervix



  • Painless cervical dilatation in the second trimester or perhaps early in the third
    trimester, with prolapse and ballooning of membrane into the vagina, followed by
    rupture of membrane and expulsion of an immature fetus


  • Etiology: previous trauma to the cervix - especially in the course of dilatation and
    curettage, conization, cauterization, or amputation, abnormal cervical
    developments

  • Treatment



    • Reinforcement of the weak cervix by some type of purse string suture
    • Contraindication - bleeding, uterine contraction, or ruptured membrane

      a. Preoperative evaluation




      • Cerclage should generally be delayed until after 14weeks so that early abortions due to other factors will be completed


      • More advanced the pregnancy, the more likely surgical intervention will
        stimulate preterm labor or membrane rupture


      • Sonography to confirm a living fetus and to exclude major fetal nomalies

      • Obvious cervical infection should be trated, and cultures for gonorrhea, chlamydia, and group B streptococci are recommanded


      • For at least a week before and after surgery , there should be no sexual
        intercourse



      b. Cerclage procedures



      • * McDonald operation
      • * Shirodkar operation
      • * modified Shirodkar procedure



      c. Complication


      • * infection


      • when performed much after 20weeks, there was a high incidence of membrane
        rupture, chorioamnionitis, and intrauterine infection
      • no evidence that prophylactic antibiotics prevent infection, or that
        progestational agents or b-mimetic drugs of any adjuvant value


9. Paternal factor




  • Chromosome translocations in the sperm
  • Adenovirus or herpes simplex virus in semen


E. Categories & Treatment of spontaneous abortion



1. Threatend abortion



  • Any bloody vaginal discharge or vaginal bleeding during the first half of pregnancy
  • Vaginal sonography, serial serum quantitative chorionic gonadotropin levels, and
    serum progesterone value have proven helpful in ascertaining if a live intrauterine
    pregnancy is present


2. Inevitable abortion




  • Gross rupture of the membrane in the presence of cervical dilatation


3. Incomplete abortion




  • When the placenta, in whole or in part, is retained in the uterus, bleeding ensues sooner or later, to produce the main sign of incomplete abortion


4. Missed abortion


  • Retention of dead products of conception in utero for several weeks

    • serious coagulation defects develop after prolonged retention of the dead fetus

    5. Recurrent spontaneous abortion



    • Three or more consecutive spontaneous abortion
    • Increased risk in a subsequent pregnancy for preterm delivery, placenta previa, breech presentation, and fetal malformation