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Miscarriage Nomenclature-A Dilemna

Miscarriage Nomenclature-A Dilemna

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Various terminologies used with respect to miscarriages are unclear, creating confusion.
So, in this blog, I am making an attempt to analyse various guidelines proposed by different organisations currently.

As per RCOG,

Miscarriage is defined as a spontaneous loss of pregnancy before 24 weeks of pregnancy.

Early Miscarriage: is defined as, spontaneous loss of a pregnancy before 12 weeks gestation.

Late miscarriage (Second trimester or mid trimester loss), refers to a miscarriage that happens when there is loss of fetal heart activity after 12 completed weeks upto 24weeks of pregnancy.
If the fetal heart activity stops at or after 24 weeks of pregnancy, this is called a stillbirth.
In UK, 24 weeks of pregnancy is the legal age of viability.


  • ACOG Practice Bulletin : ACOG Practice Bulletin was developed by the committee on Practice Bulletins – Gynaecology, with the assistance of Sarah Prager, M.D; Vanessa K. Dalton, M.D, MPH; and Rebecca H. Allen, MD, MPH.
    The information is put to help practitioners to make decisions about appropriate gynaecological and obstetric care. ACOG says, these guidelines should not be construed as dictating an exclusive course of treatment or procedure. Variations in practice may be warranted based on the needs of the individual patient, resources and limitations unique to the institution or type of practice.
    ACOG further says, early pregnancy loss, or loss of an intrauterinepregnancy within the first trimester, is encountered commonly in clinical practice. Obstetricians and Gynaecologists should understand the use of various diagnostics tools to differentiate between viable and nonviable pregnancies and offer the full range of therapeutic options to the patients, including expectant, medical, and surgical management. The purpose of the Practice Bulletin is to review diagnostic approaches and describe options for management of early pregnancy loss.
  • ACOG Definition of early pregnancy loss: Early pregnancy loss is defined as a nonviable, intrauterine pregnancy with either an empty gestational sac or a gestational sac containing an embryo without fetal heart activity within the first 12.6/7 weeks of gestation. (1)
    In the first trimester, the terms miscarriage, spontaneous abortion, and early pregnancy loss are used interchangeably, and there is no consensus on the terminology in literature. However, early pregnancy loss will be the term used in the Practice Bulletin.
    A patient however, presents with a period of amenorrhea or a positive pregnancy test, pain andor bleeding
    • Introduction : With the availability of urine pregnancy tests and beta hCG test, biochemical or clinical pregnancieshave become one important definition.All pregnancies seem to be initially biochemical
    • Process of implantation : Implantation is initiated when the blastocyst comes in contact with the uterine wall. The blastocyst hatches.Lytic factors in the uterine cavity as well as factors within the blastocyst are essential for this process.The very first connection between the blastocyst and the endometrium is called apposition which is a loose connection.
      After various signals between the endometrium &blastocyst, adhesion forms which is more stronger than apposition.
      The syncitotrophoblast continues to invade the endometrium. The blastocyst produces several autocrine factors, targeting itself and stimulating it to further invade the endometrium

Further secretions produce following effects :

  1. Loosen decidual cells from each other
  2. Prevent the embryo from being rejected by the mother
  3. Trigger final decidualization&prevents menstruation.
  • Role of Human chorionic gonadotropin (HCG) :
    Human chorionic gonadotropin (HCG) is an autocrine growth factor for the blastocyst.So, a biochemical pregnancy indicates that implantation has occurredand the HCG has begun to be secreted in the mother’s blood stream. These levels are initially quite low but as the pregnancy becomes more established, the levels will rise at more predictable rates by roughly doubling every 48-72 hours.
  • Biochemical phase of pregnancy
    The early stage of pregnancy is called BIOCHEMICAL PHASE because the only way we know the person is pregnant, is by doing biochemical blood or urine test. With extremely rare exceptions, pregnancy is the only time beta hCG is secreted into blood stream.
  • Clinical Pregnancy
    The phase of pregnancy which follows the biochemical phase is referredas clinical pregnancy.So, a biochemical phase refers to the stage of pregnancy from the time of implantation, until there is evidence by ultrasound (usually beta hCG> 2000miu/ml) or Doppler testing (to hear heart beats) and ultimately by physical inspection of the mother i.e.CLINICAL PREGNANCY.
  • Significance of Biochemical pregnancy
    If for any reason the pregnancy fails to progress it is said that the person has a biochemical pregnancy.A biochemical pregnancy is a real pregnancy because it indicates that the embryo has implanted and autocrine secretion of HCG hormone by the blastocyst for its own growth has begun, and the hormone was detected in the mother’s blood.

Unfortunately, we do not know in biochemical pregnancies, where the implantation has occurred i.e. uterus or fallopian tube. So in these cases if biochemical pregnancy has happened, it could mean early intrauterine miscarriage or early tubal abortion.

It is estimated that biochemical pregnancies occur in upto or more than 60% of all pregnancies in humans. However, because of availability of beta hCG blood testing in all patients i.e. thoseconceiving spontaneously or by fertility treatment, biochemical pregnancies have become more common.

Biochemical pregnancy is frequently a retrospective diagnosis. When the blood test is a positive, all we know is that the patient is in the biochemical phase, of what we hope will become a clinical pregnancy. If the patient loses the pregnancy in the biochemical phase, we can say in retrospect that she had a biochemical pregnancy.

The causes for biochemical pregnancy could be similar to those causing clinical miscarriages

Biochemicl Pregnancy  And Repeated Pregnancy Loss ( RPL) :

It has been always a matter of debate whether biochemical pregnancy losses should be considered as part of the definition of RPL. ASRM states that pregnancy losses should include only those that can be documented by ultrasound or histopathology(2).

Biochemical pregnancy losses are very common in general population, with almost 60-80% of pregnancies thought to end in an early pre-clinical loss (3, 4). Another study shows that almost 20% of women in the general population may experience 3 biochemical pregnancy losses due to chance alone and do not require investigations. In spite of this, biochemical pregnancies are included as a part of definition of RPL by many clinicians, as women do sensitive, over the counter urine pregnancy test to confirm biochemical pregnancy, and are anxious to undergo investigative evaluation of RPL.

In a recent study from the European Society for Human Reproduction and Embryology (ESHRE) Early Pregnancies Special Interest Group found that, in patients with RPL, each early pregnancy loss confirmed only by a positive Beta-hCG test has a negative prognostic impact equal to that of a clinical miscarriage (5). This supports the concept that biochemical pregnancies should be included in the RPL diagnosis.

Various Definitions mentioned above are a bit confusing. Hence I feel any pregnancy loss before 24 weeks, with or without fetal heart, should be labeled as miscarriage.


  1. National Institute for Health and Clinical Excellence. Ectopic pregnancy and miscarriage: diagnosis and initial management in early pregnancy of ectopic pregnancy and miscarriage. NICE Clinical Guideline 154. Manchester (UK): NICE 2012
    Available   http://www.nice.org.uk/guidance/cg154/resources/guidance-ectopic-pregnancy-and miscarriage-pdf.
    Retrieved January 20, 2015 (level |||)
  2. Failure to achieve pregnancy after eight or more transfers of eight cell embryos or five or more blastocyst transfers [26].
  3. Failure to achieve pregnancy after three single embryo transfer with good quality embryo (2006) [30].
  4. Failure to achieve pregnancy after three or more ET or four embryos in a women less than 40 years of age (2014) [23].
  5. Recommendation of Istanbul Consensus : Failure of implantation of good quality embryo. Evaluation of good quality embryo should include morphokinetic assessment and ploidy status [31].

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