REGULATIONS ON PREGNANCY AND IONISING RADIATION
Introduction
Working with radioactive substance and ionising radiation emitting devices involves a certain
element of risk. The law stipulates that persons carrying out activities with ionising radiation
emitting substances or devices must be informed and instructed beforehand. For these
reasons, the institutions on the ‘Randwyck’ site have imposed a compulsory training course
for exposed members of staff in the field of radiation hygiene, to at least knowledge level 5 or
equivalent. As part of this training course, the risks posed to exposed members of staff will
be examined, but also, in the case of pregnancy, to the unborn child.
This regulation explains the risks of exposure to ionising radiation during pregnancy once
again. In addition, an overview of the limits, conditions and recommendations applicable to
the pregnant exposed member of staff is (also) provided.
If more information is required, the on-site coordinating or general radiation expert of the
institution may be consulted.
Biological effects of ionising radiation:
In the case of interaction with biological material, such as tissue, ionising radiation causes
ionisation which leads to damage in DNA. As a consequence of this damage, the following
effects may occur in cells or tissue:
 The damage is repaired by the cell itself and no further effects are noticeable.
 The damage is not repaired, or not repaired effectively, which results in a permanent
change to the DNA. Over time, this may lead to cancer in the exposed person, or to
genetic abnormalities in offspring. In this case, we refer to stochastic or chance
effects.
 The damage is such that death of cells occurs. Irrespective of the number of
damaged cells, this may give rise to the loss of function of a particular organ. This
effect only occurs if a defined threshold dosage is exceeded, and is classed as a
deterministic effect. The dosage limits applied to exposed employees aim to prevent
these effects; therefore, under normal working conditions, these effects do not usually
occur.
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Exposure of pregnant member of staff: effects and risks
In the event of pregnancy, it is not only the member of staff who is exposed to radiation, the
unborn child may also be exposed during activities involving the use of ionising radiation
emitting substances and/or devices that are carried out by the mother. Consequently, the
pregnant member of staff deserves particular attention when it comes to protection against
radiation; on the one hand as the quickly dividing tissue of unborn children is more sensitive
to radiation than the tissue of the fully-grown mother, and on the other hand as the unborn
children do not freely choose to be exposed to radiation.
A great deal of research has been carried out into the potential effects of ionising radiation on
the unborn child, including amongst victims of the atomic bombs dropped on Hiroshima and
Nagasaki, as well as in a considerable number of animal and laboratory experiments. Using
this research, risk values have been compiled for irradiation of the unborn child in various
stages of development and at different dosage levels.
During pregnancy, the following stages of development and the corresponding effects are
recognised:
 The pre-implantation period: this covers the period from conception to 2 weeks
afterwards. At this stage, the number of cells in the embryo is still low and cannot be
differentiated. In this case, irradiation above a threshold dosage of 100 – 200 mSv will
give rise to an all or nothing effect and the foetus will either die or continue to develop
without any further damage.
 The organogenesis: this period covers the 3rd to 8th week of pregnancy after
conception and involves cell differentiation and the development of organs. If the
threshold dosage of 100 mSv that applies to this period is exceeded, abnormalities or
deformities may occur.
 Development of the brain: The brain begins to develop from the 8th to 25th week after
conception. Irradiation at this stage above the threshold dosage of 100 – 310 mSv
may give rise to a reduced IQ or mental retardment. The period after conception that
covers weeks 8 to 15 inclusive is therefore a more sensitive period that the period
from 16 to 25 weeks.
The effects detailed above are all deterministic in nature and, consequently, they only occur
if exposure exceeds a certain threshold dosage.
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In the event of exposure to radiation during pregnancy, chance effects are deemed to exist.
These are not linked to a certain period and there is no threshold dosage:
 During the entire course of pregnancy, exposure to radiation may cause DNA damage to
occur in the uterus, which may lead to cancer at a young or old age. No threshold dosage
could be determined for this effect. The additional chance of developing cancer as a
result of radiation is estimated to be 2-5 cases per 100,000 children born when exposed
to 1 mSv. If damage is sustained to the reproductive cells, this may give rise to genetic
effects in the offspring of the unborn child. The chance is estimated to be 1 in 100,000
when exposed to 1 mSv.
These data have been collated in the following table:
Time after
conception
[weeks]
Effect
0-2
Pre-natal mortality
100-200
1.10-3
3-8
Deformities/
abnormalities
Reduction in IQ/
mental retardment
Reduction in IQ/
mental retardment
100
5.10-4
100
4.10-4
100-310
1.10-4
8-15
16-25
Threshold
dosage
[mGy]
Risk value*
[chance per
mSv]
0-38
Childhood cancer
None
2.10-5 - 5.10-5
0-38
Genetic effects
None
1.10-5
* this is an estimate of the risk value above the threshold dosage stated
These risk values must always be proportionate to the natural risk values for abnormalities
and genetic effects, such as:

The chance of spontaneous miscarriage in the pre-implantation period: naturally 50%;

Chance of mental retardment: naturally 3%.
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The following table provides a comparison of effects induced by ionising radiation with the
resulting abnormalities that are caused by a variety of other factors.
Cause
Deterministic effect
Mother smokes cigarettes
Mother consumes alcohol
2 glasses per day
2-4 glasses per day
>4 glasses per day
Mother’s age
20 years
35-39 years
Various unknown causes
Irradiation of embryo: 1
mSv
Low weight at birth
20
Low weight at birth
Growth defect/brain damage
Growth defect/brain damage
10
10
20
Irradiation of embryo: 50
mSv
Pre-natal mortality
5
Cause
Stochastic effect
Incidence [%]
Various causes
Irradiation of foetus (1
mSv)
Mortality due to childhood cancer
Mortality due to childhood cancer
Down’s syndrome
Down’s syndrome
Spontaneous miscarriage
None
Incidence [%]
0.04
1.5
30-50
-
0.075 (UK)
0.002-0.005
Dosage limits
In order to protect the pregnant member of staff and her unborn child as effectively as
possible, a dosage limit has been set for the period of pregnancy. Article 80 of the Radiation
Protection Decree (3/2002) stipulates that:
'the proprietor shall ensure that the working conditions for the pregnant member of staff are
such that the equivalent dosage to the child, as the result of the work being carried out, is as
low as reasonably possible and that it is unlikely that this dosage shall exceed 1 mSV from the
moment that the member of staff makes her pregnancy known until the end of the pregnancy'.
This dosage limit helps to prevent the occurrence of deterministic effects (with threshold
dosage) and restricts the risk of chance effects such as cancer. In order to protect unborn
children as effectively as possible, it is vital that pregnancy is made known to the manager
and supervising expert at as early a stage as possible, so that consultation can take place
with regard to the required and/or requested dosage restricting measures that must be
implemented.
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In general, 'A activities’ and/or activities undertaken in controlled zones, are not allowed to be
carried out by pregnant members of staff.
Activities of this nature might include the following:
 Pregnant members of staff may not prepare radiopharmaceuticals in the azM
department of Nuclear Medicine
 Pregnant members of staff may not undertake labelling with volatile iodine within the
RNL department of UM
 The MAASTRO clinic observes the guideline that stipulates that pregnant members of
staff may not undertake activities with accelerators that generate photons with energy
in excess of 12 MV
 Pregnant members of staff may only carry out activities in the azM Radiology
department with X-ray equipment that can be operated from behind a lead screen.
If standard radiation hygiene is borne in mind, the majority of B activities can be undertaken
as normal. In general, exposed members of staff of UM and azM undertaking standard
activities with radioactive sources are subject to an effective annual dosage that does not
exceed a value of 1 mSv. This means that not all activities involving ionising radiation
emitting substances or devices are, by definition, prohibited for pregnant members of staff.
The policy in place allows consultation with the manager and recommendations from the
radiation expert on the basis of risk calculations to determine the boundaries and any
measures that may be necessary,
Consultation is always required for B activities.
The following table provides an overview of the dosage limits that are applicable to the
public, exposed members of staff and pregnant members of staff.
Target Group
Effective annual dosage as
a result of living in the
Netherlands
Annual dosage limit for
exposure as a result of rad.
activities
Members of the population
Exposed B member of staff
~2.0 mSv
~2.0 mSv
1 mSv
6 mSv
Exposed A member of staff
Pregnant member of staff
~2.0 mSv
~2.0 mSv
20 mSv
1 mSv (during pregnancy)
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Breast feeding
During the period that the mother is breast feeding, additional attention must be devoted to
preventing contamination of the mother's body with radioactive substances, in view of the
fact that these substances may be transferred to the child through breast feeding. Article 80
of the Radiation Protection Decree stipulates that: ‘the proprietor shall ensure that the
member of staff, if she is breast feeding, is exempt from activities that involve a risk of
radioactive contamination of the body that can be considered to be more than a minor risk’.
Limits have been set for the quantities of radioactive substances, in the form of an unsealed
radioactive source, that may be handled during a period of breast feeding. Additional
consultation with the manager and radiation expert shall be required in order to reduce the
risks as effectively as possible.
Conclusion
These regulations are intended to provide clarification and information with regard to the
risks that are associated with undertaking activities involving radioactive substances or
devices which emit ionising radiation during pregnancy and a subsequent period of breast
feeding. In order to be able to implement protective measures as effectively as possible, it is
vital that the member of staff contacts the manager and radiation expert at as early a stage of
the pregnancy as possible. In any case, the radiation expert shall always be available for a
private consultation to examine the specific situation and to respond to queries that have not
been covered by these regulations.
Literature
The following publications have been used when compiling these regulations:
 Eggels-Hofman C.J.J. and Kicken P.J.H: ‘Stralingsbescherming voor zwangere vrouwen
in een medische omgeving’ [Protection against radiation for pregnant women in a medical
environment].
 ICRP, International Commission on Radiological Protection; Pregnancy and Medical
Radiation. ICRP Publication 84.
 Leijen C: ‘Radiologisch werk tijdens en na de zwangerschap’ [Radiological work during
and after pregnancy].
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