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The unusual causes for recurrent pregnancy loss that are not included
in other sections include:
- debilitating maternal disease states
- substance abuse with either heavy smoking, alcohol or drug
abuse
- irradiation or exposure to chemical toxins
- medications known to be teratogenic
Any life threatening maternal disease can compromise reproductive
performance either through an ovulatory dysfunction or immunologic
disorder. Additionally, women with insulin dependent Diabetes
Mellitus who are in poor control have a greater spontaneous abortion
rate while those in good control most likely do not have an increased
rate. The glycosylated hemoglobin level is a reasonably good assessment
of longer term control, and several reports agree that spontaneous
abortion rates increase as the glycosylated hemoglobin becomes
increasingly abnormal (especially when greater than 3-4 standard
deviations over the mean).
Substance abuse is associated with spontaneous abortion. Cigarette
smoking is associated with an increase in chromosomally normal
spontaneous losses, implying a direct effect on the fetus. Alcohol
abuse has been associated with spontaneous abortion if in high
quantities, but results within this literature on alcohol are
occasionally conflicting (generally excessive consumption is drinking
at least 2-3 times per week). Illicit drug abuse affects ovulation
and can result in an ovulatory dysfunction. Little is known about
the early effects of these drugs on pregnancy and their association
to spontaneous abortion.
Industrial or environmental toxins associated with recurrent pregnancy
loss include arsenic, benzene, ethylene oxide, formaldehyde, and
lead. There has been a concern especially among health care professionals
regarding anesthetic gases and miscarriage, with mixed findings
in the literature making it prudent to avoid routine intense exposure
if possible. Irradiation during diagnostic studies with a total
exposure of less than 10 rads is thought to confer only a small
increase in risk of spontaneous abortion.
Medications taken during pregnancy should be reviewed with an
obstetrician. The current understanding of the effect of drugs
on pregnancy include
- from the time of conception (about day 14 of a 28 day cycle)
until about 2 weeks later (31 days gestation in a 28 day cycle)
harmful effects of drugs typically have an "all or none"
effect on pregnancy. This means that if there is a damaging effect
then the pregnancy is generally lost while if the pregnancy goes
on then there are typically no anomalies.
- the classic teratogenic period is from 31 days gestation (in
a 28 day cycle) to 71 days gestation (about 10 weeks gestation),
during which time damage can occur to specific organs as they
form and fetal anomalies may result.
- after the classic teratogenic period there is still significant
development of the brain, which is possibly affected by medications
The FDA (Food and Drug Administration) uses 5 categories of labeling
for drugs in pregnancy, including
- "A": controlled studies in women fail to demonstrate
a risk to the fetus in the first trimester, and the possibility
of fetal harm appears remote
- "B": animal studies do not indicate a risk to the
fetus and there are no controlled human studies, or animal studies
do show an adverse effect on the fetus but well controlled studies
in pregnant women have failed to demonstrate a risk to the fetus
- "C": studies have shown the drug to have animal
teratogenic or embryocidal effects, but no controlled studies
are available in women or no studies are available in either animals
or women
- "D": positive evidence of human fetal risk exists,
but benefits in certain situations (eg., life threatening situations
or serious diseases for which safer drugs cannot be used or are
ineffective) may make use of the drug acceptable despite the risks
- "X": studies in animals or humans have demonstrated
fetal abnormalities, or evidence demonstrates fetal risk based
on human experience, or both and the risk clearly outweighs any
possible benefits
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