Embryonic abortion is a type of spontaneous miscarriage that occurs in the early stages of pregnancy (before the end of the 13th week of gestation) when the embryo or fetus dies and remains in the uterine cavity before being expelled spontaneously. ultrasound shows a fetal bud or fetal morphology in the gestational sac, no fetal heartbeat or a blighted sac. Clinical manifestations are a normal early pregnancy process (history of menopause, elevated blood or urine hCG), symptoms of preterm abortion (vaginal bleeding, abdominal pain) or no symptoms at all.
Diagnosis of embryonic abortion
The diagnosis of embryonic abortion is based mainly on ultrasound findings.
Transvaginal ultrasound.
(1) embryo length ≤5mm, no heart tube pulsation, and still no heart tube pulsation on re-examination after 7-10 days.
(2) embryos >5mm in length without heart tube pulsation or gestational sacs >20mm in average internal diameter without yolk sac and embryo.
(3) The average internal diameter of the gestational sac is ≤20 mm without yolk sac and embryo, and the yolk sac and embryo are still absent on review after 1-2 weeks.
Transabdominal ultrasound.
(1) embryo length ≤9mm, no heart tube pulsation, and still no heart tube pulsation on review after 7-10 days.
(2) Embryo length >9 mm without cardiac tube pulsation or gestational sac mean internal diameter >25 mm without yolk sac and embryo.
(3) The average internal diameter of the gestational sac is ≤25mm without yolk sac and embryo, and the yolk sac and embryo are still absent on review after 1-2 weeks.
Factors associated with embryonic abortion
The causes of embryonic abortion are the same as those of spontaneous miscarriage and include both embryonic and maternal factors. In addition, the influence of environmental factors should not be ignored.
1. Embryonic factors
Embryonic chromosomal abnormalities are the main cause of miscarriage. Early miscarriage has chromosomal abnormalities in 50-60% of the offspring. Chromosomal abnormalities can be passed on to the offspring by either spouse, leading to miscarriage.
Chromosomal abnormalities include: numerical abnormalities and structural abnormalities. The common chromosome number abnormalities are trisomy, haploid X, triploidy and tetraploidy; chromosome structure abnormalities include chromosome deletions, overlap, inversions and balanced translocations, with inversions and balanced translocations being the most common. It has been reported that a higher percentage of chromosomes are caused by inter-arm inversions of chromosome 9. In addition to genetic factors, infection, drugs and other adverse effects can also cause chromosomal abnormalities in the offspring.
2.Maternal factors
Anatomical abnormalities
Anatomical abnormalities account for about 10-15% of embryonic abortions, including
① congenital uterine development abnormalities: unicornuate uterus, double uterus, uterine longitudinal septum, etc.
(ii) uterine anomalies due to acquired factors: uterine adhesions, submucosal or intermuscular fibroids, etc.
③Cervical factors: severe cervical laceration, cervical insufficiency, etc. (causing late miscarriage).
3.Infection factors
Infectious factors account for about 15-30% of patients with embryonic abortion. Common pathogens include: Chlamydia, Mycoplasma, Toxoplasma, Cytomegalovirus, Gardnerella infection, etc. Infection of the uterine cavity by vaginal pathogens can produce inflammation of the uterine cavity, destroy the tissue structure of the amniotic membrane and chorionic villus, reduce the tissue function, impair the growth of pregnancy tissue and lead to embryonic development arrest.
4.Endocrine factors
The effects of endocrine factors are manifested as follows
① Luteal insufficiency may cause early miscarriage.
(2) Polycystic ovary syndrome can affect the quality of eggs and embryos on one hand, and on the other hand, it can lead to a decrease in endometrial tolerance and cause miscarriage.
(3) Hypothyroidism and severe diabetes mellitus with uncontrolled blood sugar can lead to miscarriage.
5. Immunological factors
Fertilized egg implantation in the mother can be regarded as a semi-allogeneic transfer phenomenon in which the embryo and the mother produce immune tolerance through a complex and special immune relationship so that the embryo is not rejected.
In normal pregnancy, paternal human leukocyte antigens stimulate maternal production of closed antibodies to obtain maternal-fetal tolerance. When the frequency of identical parental HLA loci is high, maternal closed antibody production is insufficient, resulting in rejection of the embryo or fetus, leading to recurrent miscarriage.
Maternal and child blood group incompatibility and excessive maternal production of antiphospholipid antibodies can lead to embryo or fetal rejection and miscarriage. In China, the ABO blood type disorder is mainly caused by the mother’s O type and the fetus’ A or B type.
6. Pre-thrombotic state
Pre-thrombotic state is a pathological process of dysfunction or dysfunction of anticoagulation, coagulation system and antifibrinolytic and fibrinolytic system caused by multiple factors. Congenital PTS is mainly caused by genetic mutations related to fibrinolysis and coagulation, while acquired PTS mainly includes various diseases that can cause hypercoagulable state, such as antiphospholipid antibody syndrome. It is believed that the hypercoagulable state of blood causes the placenta to form local microthrombi, which can lead to a decrease in placental blood supply and even placental infarction, resulting in embryonic or fetal ischemia and hypoxia, and thus embryonic abortion.
7.Environmental factors
Heavy metals (arsenic, lead, etc.), indoor decoration materials (formaldehyde, benzene, etc.), environmental endocrine disruptors (bisphenol A, phthalates) and other chemical substances, as well as atmospheric pollution are associated with miscarriage.
8.Other
Psychological factors, bad habits (smoking, alcoholism, obesity, etc.) have also been reported to cause miscarriage.