Abortion (miscarriage)- Basics & Causes

Introduction

Abortion is the expulsion or extraction from its mother of an embryo or fetus at less than 20 weeks, or weighing 500 g or less when it is not capable of independent survival.
Period of viability depends on the medical facilities of a country and hence varies.
As per WHO-22 weeks.
As per ACOG-24 weeks.
In India: beyond 28 weeks, Fetus is l00% viable.
Recurrent abortion: RPL recurrent pregnancy loss. It is defined as a sequence of three or more consecutive spontaneous abortions before 20 weeks. American society for reproductive medicine (2013) defines RPL as 2 or more failed pregnancies confirmed by USG or histologically.

Incidence

10-20%
75% of abortions occur before the 16th week and of those, about 75% occur before the 8th week of pregnancy.

Weight of fetus

At 20 weeks, the weight of fetus-300 gm
Between 22-23 weeks-500 gm.
At 24 weeks, the weight of fetus-630 gms.
At 28 weeks, the weight of fetus-1 kg
500 g of fetal development is attained approximately 22 weeks (154 days) of gestation.

Classification

Abortion can be broadly classified into Spontaneous & Induced abortion.
Spontaneous abortion can be divided into Isolated and Recurrent abortions.
Recurrent Abortions/ isolated abortion is further divided into:-

Causes of abortion

Factors	Condition	causes
Fetal factors		Chromosomal abnormalities (M/C cause) Hydropic degeneration of villi Multiple pregnancy
Maternal factors	Maternal infections	TORCH infections Malaria Ureaplasma Chlamydia Brucella Spirochaetes
	Maternal medical disorders	Hypertension Chronic renal disease Cyanotic heart disease Hemoglobinopathies.
	Environmental factors	Alcohol Smoking (leads to early pregnancy loss) Caffeine
	Exposure to radiation	(> 5 rads) and anesthetic gases.
	Endocrine problems	Luteal phase defect (deficiency of progesterone). Thyroid abnormalities – hypothyroidism. Poorly controlled diabetes mellitus. PCOD Hyperprolactinemia
	Immunological causes	Antiphospholipid antibody syndrome (APLA syndrome) Inherited thrombophilias
	Uterine factors like	Cervical incompetence Mullerian anomalies (M/C associated with abortions is the septate uterus) Large and multiple submucous leiomyomas. Asherman syndrome DES exposure in utero
	Weight of mother	Underweight or nutritional deficiency does not lead to abortion. Obesity leads to abortion
	Others	Trauma Subchorionic hematoma Defective placentation
Paternal factors		Increased paternal age is associated with increased abortion

Mnemonic To Remember Maternal Causes Of Abortion

TIMED ‘O’ – T = Trauma (Leads to second-trimester loss)

I² = Infections/immunological causes

M = Maternal medical diseases

E² = Environmental factors/endocrine problem

D = Developmental/anatomical problems

O = Obesity in mother

Abortion is the expulsion or extraction of a fetus
As per WHO-22 weeks, As per ACOG-24 weeks, In India: beyond 28 weeks.
At 20 weeks, the weight of fetus-300 gm, between 22-23 weeks-500 gm.
At 24 weeks, the weight of fetus-630 gms, At 28 weeks, the weight of fetus-1 kg.
M/C cause is Chromosomal abnormalities.
Smoking & alcohol can cause abortion.
Increased paternal age is associated with increased abortion.
Mullerian anomalies (M/C associated with abortions is the septate uterus).
Trauma can lead to a second-trimester loss.

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