NOVAK 2003
Recurrent Pregnancy Loss
CONTENTS Introduction Etiology Evaluation Treatment
INTRODUCTION
70% of pregnancies are lost<viability50%<”””””””””””””””””””””””“ 1st missed period
31% ”””””””””””””””””””“> implantation(by β-HCG)
15% < ’”””””””””””””””””””””” 20 weeks
Definition: ≥3 spontaneous abortions < 20 weeks
= %1:300
Risk of recurrence : >2 abortions = 24%
> 3 = ”””””””””“ 30% > 4 = ”””””””””“ 40-50%
Evaluate RPL after 2 spontaneous abortions if: age > 35 years subfertility/infertility FHMs are seen in both
=1% of pregnancies require evaluation.
ETIOLOGY
1) Genetic = 3.5-5%2) Anatomical = 12-16%3) Endocrine = 17-20%4) Infection = 0.5-5%5) Immunological = 20-50%6) Others = 10%
10-15% of RPL is due to APAS and chromosomal
abnormalities.
GENETIC CAUSES Mostly due to balanced translocation :
Reciprocal translocation normal gametesRobertsonian translocationbalanced gametes
or unbalanced gametes Most embryos with chromosomal abnormalities
do not survive.Live offspring are either carriers of:
Balanced translocation Monosomy/trisomy ( in robertsonian T ).
Monosomic fetuses : may be mosaic
X gametes can only survive ↑in IVF
Trisomic fetuses : may also be mosaic.
include trisomies 13,16,18,and 21 survive more
than monosomic fetuses
We can't exclude chromosomal abnormalities by : negative family history history of a live term birth
The frequency of chromosomal abnormalities is inversely proportional to the number of previous abortions.
Couples with genetic abnormalities are usually with no children .
Parents with history of: spontaneous abortion ± SB ± live birth ( ± anomalies )
are candidates for parental karyotype, but this may be insufficient because:
o aneuploid sperm may be motileo chromosomal abnormality may be in 1
sperm
Other structural chromosomal anomalies include:• Inversion• Insertion• Chromosomal mosaicism• X-linked anomalies (males do not
survive)• Single gene anomalies such as cystic
fibrosis (detected by detailed family history).
HERITABLE THROMBOPHILIAS
1. Hyperhomocysteinemia mutation2. Antithrombin III mutation3. Protein-C and protein-S deficiency4. Factor V Leiden mutation5. Prothombin mutation6. Factor XII deficiency7. Factor XIII and fibrinogen defects
1 -HYPERHOMOCYCTEINEMIA
Homocysteine is derived from dietary methionine. It is metabolized in the presence of methyl-tetra-hydro-folate reductase enzyme (MTHFR) + dietary folic acid, vit B6, vit B12 into:
Cystathione or back into methionine .Hyperhomocysteinemia may be either:
- Congenital due to point mutation in MTHFR (common )
- Acquired due to dietary deficiency of folic acid, vit B6, or
vit B12Hyperhomocysteinemia is linked to thrombosis and RPL.
2 -ANTITHROMBIN III MUTATION
Antithrombin III inhibits: - thrombin
- factor IXa,Xa,XIa,XIIaAntithrombin III mutation is rare but it is the worst prognostic factor of all heritable thrombophilias. It is associated with RPL and thrombosis.
3 -PROTEIN-C AND PROTEIN-S DEFICIENCY
Protein-C and protein S affect: - X Xa reaction
- prothrombin thrombin reaction
Protein-C and protein S deficiency is linked to placental thrombosis and pregnancy complications.
4 –FACTOR V LEIDEN MUTATION
Factor V prevents interaction with protein-C. Multiple point mutation in the cleavage site of factor V Leiden resistance to protein-C.
Factor V Leiden is associated with RPL .
It is the most common heritable thrombophilia among white people.
5 –PROTHROMBIN MUTATION
It is linked to thrombosis and pregnancy loss.
6 –FACTOR XII DEFICIENCY
Increase in Japanese people and is linked to recurrent pregnancy loss.
7 -FACTOR XIII AND FIBRINOGEN DEFECTS
Both are associated with fetal loss andinvolve other complex mechanisms than simple thrombosis and infarction.
II-ANATOMICAL CAUSES1 -Congenital causes:
incomplete fusion of Mϋllerian ducts incomplete septum resorption (septate, subseptate) cervical anomalies
The most commonest anomalies are septate 60% of spontaneous abortion in the 2nd trimester and sometimes the 1st trimester. Inutero exposure to DES may cause congenital anomalies. The most common lesion in DES is hypopleasia abortion in the 1st or 2nd trimesters.
2 -Acquired causes: fibroid polyps adenomyosis Asherman syndrom cervical incompetence
III- ENDOCRINE CAUSES
Endocrine changes of menstrual cycle
Endocrine factors:1. Luteal phase defect2. Diabetes3. Thyroid disease4. Hyperprolactinemia5. Ovarian reserve
ENDOCRINE CHANGES OF MENSTRUAL CYCLE
Follicular phase and ovulation: - abnormal blastocyst transport
- alteration of uterine receptivity - improper function of CL
From ovulation until 7-9 weeks - failure of CL to produce enough P
- impaired delivery of P to the uterus - inappropriate use of P by the decidua
Near the time of luteal-placental shift - trophoblast unable to produce biologically active
P
ENDOCRINE FACTORS:1- LPD
It is inadequate or inappropriately timed endometrial maturation due to:
- Premature aging of the oocyte
- Dyssynchronous maturation of the endometrium
- PCO : . PCO is present in 80%of RPL
. It is associated with : , obesity
, ↑androgen level affect markers of
uterine receptivity , ↑insulin resistance
2 -DIABETESDM type II
↑spontaneous abortion
IDDM: - Pregestational glycemic threshold above
which abortion ↑ - Hyperglycemia damage the embryo
- Vascular changes in advanced IDDM ↓placental blood flow.
3 – THYROID DISEASEOvulatory disfunction
LPD Pregnancy is associated with ↑ requirement
to T4. Hypothyroidism is associated with ↑ spontaneous abortion .
Even when T4 is normal, ↑ antithyroid antibodies may cause ↑ RPL.
(Antithyroid antibodies could be markers of a generalized autoimmune disease .)
4 - HYPERPROLACTINEMIA
Affect reproduction by:
- Direct effect on endometrium
- Indirect immuno-mediator
effect .
5 – DIMINISHED OVERIAN RESERVE
Can be evaluated by:
- Day 3 FSH - Day 3 estradiol
- CC challenge test .
4 - INFECTIONMycoplasmaUreaplasmaChlamydiaβ-streptococcus:
BV is linked to ↑ RPL and PTL in a large study.Viral infection as:
- cyromegalovirus - herpes simplex
Mechanisms of action: - villitis
- mechanisms protecting the fetus from autoimmune rejection↑ infection
- activation of immune reactions PTL, PROM, IUGR.
5 – IMMUNE CAUSES
I. Basic immunologyII. Cellular immunityIII. Humoral immunity
I - BASIC IMMUNOLOGY1 -Innate responses:
1st line defense .None antigen specific.Mechanisms are :
- phagocytosis - complement fixation ,
- lysis by NK cells .2 -Acquired responses:
Antigen-specific .Modulated by T and B cells.Divided into:
- Primary immune response: on 1st contact with the Ag - Secondary immune response: on subsequent contact with the
Ag. Rapid and strong .
ANTIGEN SPECIFICITY Regulated by 2 sets of genes present at major histocompatability
complex (MHC) located on chromosome 6:
Class I MHC molecules: HLA A, B, C Present at the surface of nearly all cells for intracellular pathogens .
Major ligand for: TCR on CD 8+ cytotoxic and suppressor cells many receptors on NK cells.
Class II MHC molecules: HLA DR, DP, DQ Present on the surface of antigen-presenting cells as :
Dendritic cells, macrophages- monocytes, B-cells, and tissue specific cells .Protect against extracellular pathogens .Major ligand for: TCR on CD-4+ T- helper cells .
EDUCATION AND HOMING Fetal bone-marrow derived T-cells move
with the blood until they reach the thymus. In the thymus they are divided into :
- Those who will express CD4 co-receptor - Those who will express CD8 co-receptor
And auto-reactivity is eliminated; that is the cells can recognize non-self but not
react against self .
MUCOSAL AND PERIPHERAL IMMUNE SYSTEMS
Peripheral immune system: Located in the blood and spleen.
Responsible for protection against blood-born pathogens.
Mucosal immune system: Located in GIT, RT, GUT, lacrimal and
mammary glands. Responsible for protection against exogenous pathogens.
II - CELLULAR IMMUNE RESPONSE
1. Resident cells2. Immune cell education and homing to
the reproductive tract 3. Antigen presentation at the maternal-
fetal interface4. Regulation of the decidual immune
cells
1 -RESIDENT CELLSThe endometrium is populated by: T-cells
NK-like cell Macrophages
Very few B-cells
At implantation, there is a dramatic change in the decidual cells and
70-80% of the cells are called: Decidual granular lymphocytes, or
Large granular, or Decidual NK
If these cells are NK, then implantation site represent the largest accumulation of NK in humans. The function of these cells is unclear.
In animals, peripheral NKT cells (which have the characteristics of both T cells and NK cells) ↑ spontaneous abortion.
Most peripheral immune system T-cells express TCR-αβ .
In the reproductive system T-cells express in addition to this TCR-γδ which ↑ early in pregnancy and are responsible for direct, none MHC restricted immune recognition of Ag within tissues = more protection.
A subset of macrophage called suppressor cells promot anti-inflammatory properties and may be implicated in maintenance of pregnancy.To sum up:
Human decidua is populated by characteristic immune cells. Alteration of these cells may pregnancy loss. Alteration of these cells occur in RPL and not isolated abortion.
2 – IMMUNE CELL EDUCATION AND HOMING
How these cells are selected, educated, and how they home to the reproductive tract is still unknown, but animal studies showed that:These cells may be educated outside the thymusThey may have different mechanisms other than MHCThey may differ from mucosal and peripheral immune systems.In the mucosal immune system, cells select these sites through interaction between:Cell surface molecules on the immune cell= integrins
””””””””””””””””””””””””””“endothelial cell= selectins or vascular wall adhesive molecule (VCAM) == homing.Animal studies showed that:Integrins are expressed in the reproductive tractKnowing the mechanism of selection and homing may aid in ttt of RPL.
3 – ANTIGEN PRESENTATION
In the past trophoblast escape recognition by ↓ expression of MHC Ag .
Now obsolete, although trophopblast cannot express class II MHC molecules and class I MHC HLA: A and B Ags.Extravillous cytotrophoblast cells express class I: C, E and D Ags. These cells are characterized by excessive invasive properties:
They move from the tip of villi deep into the decidua, invade decidual blood vessels, and replace endothelial cells of decidual spiral arteries. Their behavior reflect non-MHC mechanisms as integrin switching and expose the fetus to recognition.
Any cell not expressing Ag is killed by NK. In addition to protection from killing by NK cells, expression of MHC HLA: C, E, and G by the trophoblast may modulate cytokines expression, aid in invasion, and aid in maternal acceptance. G
Ag was linked to disorders of placental invasion . MHC polymorphism was not linked to RPL.
Interferon-γ was believed to ↑ spontaneous abortion by ↑
expresion of class I and class II MHC which ↑ cytotoxic attack of T cells ,
but aborted tissues were not shown to express MHC Ags.
Class II genotypes were linked to adverse pregnancy outcome, RPA, and ↑ susceptibility to disease as autoimmune disease and DM.
4 –REGULATION OF DECIDUAL IMMUNE CELLS
I. Alterations in T- helper cell phenotype
II. Reproductive hormones and immunosuppression
III. Tryptophan metabolism
I –ALTERATION IN T-HELPER CELL PHENOTYPE Ag-stimulated immune responses involving CD4+ cells can be
divided into: T-helper cell subset 1 (TH1) T-helper cell subset 2 (TH2)
based on the character of CD4+ cell and associated cytokine .
Undifferentiated T- helper cells are differentiated into:
TH 1 in the presence of interferon γ (INF-γ). TH 1 is associated with inflammatory responses and:
INF-γ, IL 2, IL 12 . TH 2 in the presence of IL 4. TH2 is associated with
antibody responses and IL 4, 5, 6, 10, TNF-β.
TNF-α is expressed by both T-helper cells.There is a reciprocal relationship between TH 1, TH 2, and
cytokines.
Most researches agree that: TH 1 responses are harmful to the embryo
TH 2 responses are present in most normal pregnancies TH 1 responses are present in some patients of RPL
60-70% of none pregnant patients with history of RPL
show abnormal T-cell responses invitro compared to <3% in controls.The type of CD4+ cellular response to the implanting fetus is controlled not only by the types of cells in the decidua but also by the cytokine enviroment at the maternal –fetal
inteface .
Cytokines may affect reproduction by regulating: Type of cytokine expressed
Concentration of cytokine expressed Differential stage of effector cell.
Cytokine alteration can be detected in: Endometrium
Decidual immune cells Peripheral blood lymphocytes
Animal studies showed that the only factor absolutely essential for implantation is :
” Leukemia inhibitory factor .“
II- REPRODUCTIVE HORMONES Many mechanisms are present to avoid fetal recognition by
the mother.
Maternal immune responses to the fetus can be detected and if these mechanisms are regulated, this may help to treat RPL.
Increased reproductive hormones during pregnancy is known to suppress maternal immunity, but the overall immune responses during pregnancy appears to change little, while local immune suppression at the maternal-fetal interface may be vital .
PROGESTERONEProgesterone is partially responsible for pregnancy maintenance .
Progestrone suppress T-cell activity by altering K-channels in cell depolarization which affect:
gene expression intracellular Ca
And both may be none receptor mediated, resulting in: TH 2 responses
LIF expressionBoth will help in maintenance.Recently it was found that progesterone can inhibit CD 8+ T cell proliferation and cytokine secretion.
ESTROGEN Estrogen modulate immune reactions.
In male animals :
Estrogen improve immune responses after hemorrhage,
trauma and thermal injury. Estrogen protect against chronic renal allograft rejection
In humans:
Estrogen ↓ delayed-type hypersensitivity
Estrogen ↑ TH 2 responses .
III – TRYPTOPHAN METABOLISM Tryptophan is important for T-cell activity and proliferation.
Local alterations in tryptophan metabolism may either : activate or
fail to suppress maternal immune response.
In animals: - Tryptophan rich diet ↑ spontaneous abortion
- Inhibition of indolamine 2,3 dioxygenase enzyme (IDO) loss of
allogeneic fetuses but not syngeneic .In humans:
- IDO is expressed in the decidua . - As GA ↑ alteration in maternal serum tryptophan level
Both= potential local immune regulation.
HUMERAL IMMUNITYI. Antiphospholipid antibody syndromeII. Antithyroid antibodiesIII. Blocking antibody deficiency theoryIV. Novel HLA-linked alloantigen
ANTIPHOSPHOLIPID ANTIBODY SYNDROMEIn the past , it was thought that these antibodies were against: cardiolipin and phosphatidylserine. Now it is believed to be against a protein cofactor : β2 glycoprotein-1Which assist antibody association with phospholipid.
%3-5
CHARACTERISTICS OF APAS: Prolonged aPTT Thrombosis Obstetric complications: Abortion Stillbirth PTL PROM IUGR Preeclampsia
SAPPORO CRITERIA FOR APAS DIAGNOSIS(1998)
clinical and ≥ laboratory criteria must be present to diagnose APAS: ≥ clinical criteria:
≥1 episode of thrombosis in artery, vein, or small vessel obstetric complication:
≥3 spontaneous abortions ≥ 10 weeks ≥1 fetal death ≥ 10 weeks
≥1 preterm labor ≥ 34 weeks for preeclampsia or placental insufficiency
laboratory criteria: 2 results must be (+)ve on ≥ 2 occasions with ≥ 6 weeks in
between+ ve ACA (Ig G or Ig M medium to high level)
+ ve LAHistory of systemic lupus erythromatosus=less favorable outcome.
MECHANISMS OF ACTIONI. ↓ prostacyclin, ↑ thromboxane thrombosis placental
infarctionII. Inhibition of syncytiotrophoblast formationIII. Increase β2 glycoprotein 1
rapid atherosclerosis in decidual artries inhibit trophoblast adhesion to
endothelial cells ↓annexin V = placental antithrombotic
molecule To summarize:Pathological evidence of APAS are often equivocalCharacteristic criteria “””””””””””””””””” lacking
””””””””””””””””””””””””””””””””””””””””“present in other lesions
ANTITHYROID ANTIBODIES
ControversialOne study link it to RPLOther study no link
BLOCKING- ANTIBODY DEFICIENCY THEORY
Studies using mixed lymphocyte culture with paternal stimulator cells suggest that HLA-sharing between the two parents may cause blocking-antibody deficiency.
Larger studies showed that HLA heterogeneity is not necessary for successful pregnancy, although complete sharing of the whole genome (occur in isolated groups of people and is very rare) is associated with ↑ spontaneous abortion. Thus, HLA-typing is rarely required.
NOVEL HLA-LINKED ALLOANTIGEN SYSTEM
Studies showed that this substance is actually CD 46 which is a placental complementary receptor responsible for protecting the placenta from complement -mediated attack.
Conclusion:Successful pregnancy may not require an intact maternal immune system.Evidence:Successful pregnancy can occur in:
Agamma-globulinemic women Severe immune deficiency Animals lacking T and C cells Animals with congenital absence of the thymus
OTHER FACTORS VEGF Apoptosis Uterine receptivity Endometrial mucin Cellular and extracellular matrix adhesion properties Soluble intercellular adhesive molecules.
Environmental factors:o Medications:
Antiprogestogens Antineoplastic agents Anhalation anesthetics Ionized radiation prolonged organic solvents
o Heavy metalso Alcoholo Coitus cause abortion only if the cervix is abnormal or
incompetent
EVALUATION
PRECONCEPTION EVALUATION History Physical examination Laboratory investigations
POSTCONCEPTIONAL EVALUATION
Β-hCG U/S Α-fetoprotein
HISTORY History of previous pathologic studies or karyotyping of
the abortus tissues. 60% of abortions < 8 weeks are due to chromosomal
abnormalities. Most common anomalies are trisomy 16 or monosomy 45X. Documentation of aneuploidy in the abortus tissues does not affect future fertility.
GA of previous abortion: Most RPL occur at the same GA every time.
Menstrual history may detect oligomenorrhia or endocrine abnormalities.
The timing of coitus in relation to fertilization may detect dyssynchronous fertilization or old ovum.
Subfertility or infertility= 33% in RPL couples. Abortion may occur before
the 1st missed period and is diagnosed as subfertility. Personal or family history of thrombosis or renal
abnormalities. Family history of pregnancy loss or obstetric complications. Drug intake or environmental exposure.
PHYSICAL EXAMINATIONGeneral examination :
Obesity Hirsuitism and acanthosis Brest examination and glactorrhea Thyroid
Pelvic examination: Anatomy: uterus size, shape, DES
cervix vagina
Trauma Infection
Estrogenization
LABORATORY ASSESSMENT
Standard investigations:I. Parental peripheral blood Karyotyping II. Hysteroscopy / HSGIII. Luteal-phase endometrial biopsy at
day 24IV. Thyroid function tests ± prolactinV. Platelet/ complete blood pictureVI. ACA+LA (aPTT or Russel viper venom)
LABORATORY ASSESSMENT UNDER INVESTIGATION
• Ovarian reserve: day 3 FSH, CC challenge test• PCO: LH, A• ATA• Autoantibodies : antiphospholipid,
antiphosphatidylserine, anti-β2 glycoprotein 1 • Nk cells activity• TH 1, TH 2• Hypercoagulability; aPTT• Hyperhomocysteinemia: fasting and after
methionine loading (dangerous to the fetus). • Cervical cultures: mycoplasma, ureaplasma,
chlamydia
EXPERIMENTAL STUDIES Mixed lymphocyte culture
Parental HLA-typing Serum or site-specific autoantibodies & alloantibodies Others:
- Suppressor cell
- Cytokines - GF
- Embryotoxic factor - Oncogenes
POSTCONCEPTIONAL EVALUATIONIf become pregnant psychological supportConfirm: - intrauterine pregnancy
- viability Because of ↑ % of ectopic and molar pregnancyPregnancy complications
Only ↑ in APAS and intrauterine infections .Monitoring:
Β-hCG Not always ↓ before abortion If missed period Β-hCG until= 1500mIU/ml U/S Every 2 weeks GA of abortion If no FH activity until 6-7 weeks terminate and karyotype Maternal serum α-fetoprotein At 16-18 weeks.
Karyotyping of the abortus tissues: - Suggest chromosomal abnormalities in the
parent - Prevent other costly investigations ↓ cost
Difficulties:
- Difficult culturing of inflamed or necrotic cells
- Contamination with maternal cellsRecent advances:
Genomic hybridization technology: Used on archived and paraffin-embedded
tissues Karyoyping of nucleated fetal RBCs in
maternal blood
TREATMENT
TREATMENTMost ttt are experimental, use only with informed consent. Most patients conceive irrespective of ttt.
Genetic causesAnatomical causesEndocrine causesInfectionImmunological ttt
immune-stimulation immune-suppression
Antithrombotic ttt
TREATMENT OF GENETIC CAUSESAntithrombotic ttt for inherited thrombophiliasPreimplantation genetic diagnosis in known heritable disordersDonor oocyte or sperm in robertsonian translocationsRecently :
PGD+antithrombotic ttt+ ART for all unexplained RPL
TREATMENT OF ANATOMICAL CAUSESHysteroscopic resection/metroplasty ± laparoscopyU/S guided transcervical metroplastyFluoroscopic guided septum resectionLaparoscopic excision of endometriotic lesionsCervical cerclage .
TREATMENT OF ENDOCRINLOLGICAL CAUSES
Ovulation inductionThyroid hormone replacementInsulin-sensitizing agents for overt DMBromocriptine
TREATMENT OF INFECTIONEmpiric antibiotics for immunosuppressive patientsSpecific antibiotic ttt for known infections to both partners with posttreatment culture before attempting conception.
TREATMENT OF IMMUNOLOGICAL CAUSESImmunostimulating ttt
leukocytes others
Immunosuppressive ttt I.V. immunoglobulin
progesterone others
cyclosporine nifedipine
corticosteroids LDA
LEUKOCYTESLarge studies uselessComplications:
Graft versus host reaction Severe IUGR Fatal fetal thrombocytopenia Autoimmune/isoimmune complications
May benefit 1 : 11 patientsRoutine use unjustified
OTHERS
I. I.V. injection of syncytiotrophoblast microvillous plasma membrane vesicles.
II. 3rd party seminal plasma suppositories.
INTRAVENOUS IMMUNOGLOBULINIndicated in:
APAS Inappropriate cellular immunity
Possible Mechanisms of action: ↓ autoantibodies ↑autoantibodies clearance T-cell regulation Complement inactivation ↑ T-cell suppressor function ↓ T-cell adhesion to extracellular matrix ↓ TH1 cytokine production
Side effects: nausea myalagias hypotension headache anaphylaxis
Disadvantages : expensive invasive time consuming require multiple I.V.D.
PROGESTERONE
Partially responsible for maintenance .Inhibits TH1 responses shift to TH2
responsesVaginal progesterone:
Is better than systemic treatment ↑ local suppression ↑ intrauterine concentrations ↓ adverse effects.
OTHERS
Cyclosporine Nifedipine Plasmaphoreses Corticosteroids:
Prednisone + low dose Aspirin same pregnancy outcome as controls, but :
↑ HTN ↑ DM ↑ PTL
ANTITHROMBOTIC TREATMENT
For APAS and thrombophilic disordersTreat hypercoagulabilityStart before conception continue although pregnancyUnfractionated heparin 5000 IU S.C. twice/day
+low dose Aspirin 75-80mg/day. Monitoring by aPTT/week.Risks:
PTL PROM IUGR Preeclampsia Abruptioplacenta Stillbirth Gastric bleeding Ostiopenia
Recently: low molecular weight heparin(LMWH) Indications:
APAS Non-APAS patients with thrombophilia Patients without thrombophilia =unexplained RPL
Advantages: Less bleeding Less osteopenia More antithrombotic ratio More patient compliance:
- less frequent doses - less frequent monitoring
The role of LDA alone:Studies useful for APAS and RPLStudies useful in unexplained RPLRoutine use alone cannot be justified.
Other antithrombotic treatment: Vit B6, B12, folate Protein C concentrate
Both for hyperhomocysteinemia whether congenital or aquired.
PROGNOSIS Depends on cause and number of abortions.
Even if >4 abortions, successful birth rate may reach 60%
Genetic causes 20-80% live birth Anatomical causes 60-90% “””””””””” Endocrine causes > 90% “””””””””” Infection 70-90% “””””””””” APAS 70-90%
“”””””””””FHM documentation:
It has a prognostic value depending on the cause :
FHM documentation in 77% of live birth ””””””””””””””””””””””“in 86% of APAS before
abortion ””””””””””””””””””””””“in 3% of unexplained RPL