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Operational Obstetrics & Gynecology

Normal Pregnancy

Watch a PowerPoint Lecture

Diagnosis of Pregnancy Disability Thermal Stress
Pregnancy Tests Maternal Skin Changes Noise
Prenatal Care Nausea Vibration
Nutrition Heartburn Solvents
Prenatal Vitamins Sciatica Heavy Metals
Laboratory Tests Carpal Tunnel Syndrome X-rays
Ultrasound Scans URI Radiation
Estimating Gestational Age Antibiotics CRT Exposure
Fetal Heart Beat Other Drugs Diving
Exercise Immunizations Hyperbaric Therapy
Aircrew Status

Diagnosis of Pregnancy

Pregnancy may be suspected in any sexually active woman, of childbearing age, whose menstrual period is delayed, particularly if combined with symptoms of early pregnancy, such as:

  • Nausea (1st trimester)
  • Breast and nipple tenderness (1st trimester)
  • Marked fatigue (1st and 3rd trimesters)
  • Urinary frequency (1st and 3rd trimesters)
  • The patient thinks she's pregnant

Early signs of pregnancy may include:

  • Blue discoloration of the cervix and vagina (Chadwick's sign)
  • Softening of the cervix (Goodell's sign)
  • Softening of the uterus (Ladin's sign and Hegar's sign)
  • Darkening of the nipples
  • Unexplained pelvic or abdominal mass

Pregnancy Tests

The diagnosis of pregnancy is accurately made with a urine pregnancy test. Current test kits are highly specific and detect 35-30 mIU of HCG (human chorionic gonadotropin, the pregnancy hormone) per ml of urine. In other words, the pregnancy test will be turning from negative to positive at about the time of the first missed menstrual period.

Collect a fresh urine specimen. First morning specimens are preferable in early pregnancy because they are more concentrated and more likely to be positive is only small amounts of pregnancy hormone are present.

Place the correct number of drops of urine in the collecting area of the test kit. The precise number of drops varies from manufacturer to manufacturer.

Wait the length of time specified by the manufacturer.

With this particular test kit, the test is read after 3 minutes. A blue line next to "Control Line" indicates that the urine has turned the control area positive. This means the test kit is working correctly.

Because there is no visible "+" in the pregnancy test area, the test results are negative...the patient is not pregnant.

In this case, the control area turned positive, indicating that the test is working correctly.

The test area demonstrates a "+." This means the test is working correctly and the results are positive...the patient is pregnant.

In the event of an "equivocal" pregnancy test...one that is not really positive nor negative, additional urine can be put through the test kit to boost the sensitivity. Instead of using 3 drops of urine, you can use up to 6 drops of urine. This will virtually double the sensitivity of the test, while increasing the chance of a false positive by only a small amount.

In an urgent situation, if a patient is unable to provide urine for the test, serum can be used in the urine test kit in place of urine.

  • Draw blood into a test tube.
  • Tape the test tube to the wall for about 10 minutes (allow it to clot).
  • Using an eye dropper or a syringe with a needle, draw off a small amount of serum (the clear, watery part of the blood that's left at the top of the test tube after the blood has clotted).
  • Use the serum instead of urine in the urine pregnancy test kit, drop for drop. If the test kit calls for 4 drops of urine, use 4 drops of serum.

This is an imperfect solution, because the forms of HCG (pregnancy hormone) found in serum are somewhat different from the forms found in urine. Further, the serum proteins tend to sludge up the test kit, both mechanically and biochemically. That said, using serum instead of urine will work well enough for most purposes in an operational setting and can provide immediate insight into the patient's problem.

Prenatal Care

Appendicitis location at 37 weeks gestation

5-Minute Pregnant Abdomen Exam
This video demonstrates the complete abdominal exam, including estimation of fetal weight, calculation of gestational age, and Leopold's Maneuvers.
www.brooksidepress.org

At the first prenatal visit, take a careful history, looking for factors that might increase the risk for the pregnant woman. Many providers use a questionnaire, filled out by the patient, as a starting point for this evaluation. A sample Prenatal Registration and Obstetrical Questionnaire form can be used for this purpose.

One important aspect of prenatal care is education of the pregnant woman about her pregnancy, danger signs, things she should do and things she should not do. Many providers find it useful to give the woman printed material covering these issues that she can take with her. This allows her to read the material at a later time and to refer to it whenever she has questions. A sample Prenatal Information form can be printed and used.

Routine visits:

  • every 4 weeks until 28 weeks' gestation
  • every 2-3 weeks until 36 weeks' gestation
  • every week from 36 weeks to delivery

At each prenatal visit:

Check weight

Typical weight gain is about a pound a week. This means 30 to 40 pounds for the entire pregnancy, although some physicians feel the ideal weight gain should be closer to 25 pounds. Weight gain is usually slow during the first 20 weeks. Then, there is usually rapid weight gain from 20 to 32 weeks. After that, weight gain generally slows and there may be little, if any weight gain during the last few weeks.

If there is insufficient weight gain (below 13 pounds), there is concern that the baby may not be getting enough food. If there is sudden weight gain (more than 2 pounds in a week or more than 6 pounds in a month), this may be associated with the development of fluid retention due to pre-eclampsia (toxemia of pregnancy).

Check blood pressure

Blood pressure in early pregnancy will reflect pre-pregnancy levels. During the 2nd trimester, maternal blood pressures usually fall below prepregnancy levels. During the 3rd trimester, blood pressure usually goes back up to the pre-pregnancy level. Any sustained BP of 140/90 or greater is considered significant and may indicate the development of pre-eclampsia.

Fundal height measurementMeasure fundal height

Use a tape measure to record the size of the uterus (technique described below). The fundal height, measured in cm, should be approximately equal to the weeks gestation, from mid-pregnancy until near term. Measurements falling within 1-3 cm of the expected value are considered normal. Fundal heights 4 cm different than expected are considered abnormal and suggest the need for further investigation.

Listen to the fetal heart with a dopplerListen for the heartbeat

The normal rate is generally considered to be between 120 and 160 beats per minute. The rates are typically higher (140-160) in early pregnancy, and lower (120-140) toward the end of pregnancy. Past term, some normal fetal heart rates fall to 110 BPM. There is no correlation between heart rate and the gender of the fetus.

Anklel edema during pregnancyCheck for edema

Swelling of the feet, ankles and hands is common during pregnancy. It can be uncomfortable for the patient, but she can be reassured that it will go away after delivery. Facial edema or any sudden increase in edema can be a sign of developing pre-eclampsia, so the BP should be checked.

An effective treatment for edema is bedrest for 2-3 days, while drinking plenty of plain water and avoiding excessive salt. This will mobilize the extracellular salt and fluids, leading to a loss of several pounds through urination. In most cases, such treatment is not necessary as the edema itself is not medically threatening.

Check protein and glucose

A urine dipstick test for protein is generally negative or trace during pregnancy. If 1+ (30 mg/dl) or more, it is considered significant.

Urine normally shows negative or trace glucose. If persistently 1/4 (250 gm/dl) or more, it is considered significant.

Ask about fetal activity

Although fetal movement can be documented by ultrasound as early as 7-8 weeks of pregnancy, fetal movement is not usually felt by the mother until the 16th week (for women who have delivered a baby) to the 20th week (for women pregnant for the first time).

Once they positively identify fetal movement, most women will acknowledge that they have been feeling the baby move for a week or two, but didn't realize that the sensation (fluttery movements) was from the baby.

Movements generally increase in strength and frequency through pregnancy, particularly at night, when the woman is at rest. At the end of pregnancy (36 weeks and beyond), there is normally a slow change in movements, with fewer violent kicks and more rolling and stretching fetal movements. A sudden decrease in fetal movement is a danger sign that needs to be reported and investigated immediately.

"Kick counts" are sometimes recommended to patients as a means of quantifying fetal movement. One common way of doing a kick count is to ask the woman to count each distinct fetal movement, starting from the time she awakens in the morning. When she reaches 10 movements or kicks, she is done counting for the day. If she gets to 12 noon and hasn't reached a count of 10 movements, she reports this to her provider and further testing is done.

Any new symptoms

The development of pain, bleeding, vaginal discharge or fluid loss, or neurologic symptoms (visual changes, disequilibrium) can be significant.

Nutrition

A pregnant woman should eat a normal, balanced diet for one person.

This may prove difficult, particularly during the early part of the pregnancy when she may experience significant nausea.

It may also prove difficult later in pregnancy when she feels hungry all the time. These women may find they do better by having more frequent (but smaller) meals, or snacks between meals of relatively nutritious but low caloric foods.

Prenatal Vitamins

It is customary for pregnant women to take a prenatal vitamin each day.

In theory, it might be possible for a pregnant woman to obtain the right amount of essential vitamins and minerals through a careful and complete diet. In real life, it is difficult for most women to achieve such a diet, particularly the need for Folate. It is far simpler take a prenatal vitamin each day.

Those living in nutritionally-deprived areas will particularly benefit from the addition of prenatal vitamins to their diet.

Laboratory Tests

Some routine lab tests are done on all pregnant women at different times during the pregnancy. Other tests are done for a specific indication.

As early in pregnancy as feasible, obtain:

  • Hemoglobin or hematocrit
  • White blood count and platelet count
  • Urinalysis
  • Blood group and Rh type
  • Atypical antibody screen
  • Rubella antibody titer
  • RPR or VDRL
  • Hepatitis B screen
  • HIV
  • Pap Smear
  • Chlamydia/Gonorrhea

Subsequent lab tests consists of:

  • Amniocentesis or CVS for women age 35 at 10-17 weeks
  • Maternal serum AFP at 16-18 weeks
  • Hemoglobin or hematocrit at 28 weeks
  • Serum glucose at 1-hour post 50g glucose load at 28 weeks
  • Administration of Rhogam to Rh negative women

Other tests may be indicated, based on individual risk factors. These might include screening for Sickle Cell disease (or trait), thalassemia, G6PD, tuberculosis. Follow-up tests may also be needed, based on the original screen. For example, a woman found to be very anemic might be evaluated with serum folate and ferritin levels. A woman failing her glucose screening test will probably need a full glucose tolerance test.

Ultrasound Scan

Routine ultrasound scanning of all pregnant women early in pregnancy is recommended by some, but not all authorities in civilian settings.

For women in an operational environment, a routine ultrasound scan early in pregnancy can be very useful, because it identifies those destined to miscarry, those with an ectopic pregnancy, and those whose gestational age does not agree with their LMP.

Additional, medically-indicated ultrasound scans may also be appropriate. Ultrasound is used to evaluate vaginal  bleeding or pain, and discrepancies between the measured size of the uterus and the expected size. It may be used to look for multiple gestations, such as twins or triplets, determine the position of the fetus, and assess fetal growth. Later in pregnancy, it may be used to evaluate fetal well-being, amniotic fluid volumes, and to estimate fetal weight.

Estimating Gestational Age

MacDonald's RuleThe estimated delivery date is calculated by adding 280 days to the first day of the last menstrual period. An alternative method of determining the due date is to add 7 days to the LMP, subtract three months, and add one year. These calculations are made easier with the use of a Gestational Age Calculator.

One way to approximate a pregnancy's current gestational age is to use a tape measure to determine the distance from the pubic bone up over the top of the uterus to the very top. That distance, measured in centimeters, is approximately equal to the weeks of gestation, from about mid-pregnancy until nearly the end of pregnancy. This is known as MacDonald's Rule.

Fundal height at different gestational agesIf a tape measure is unavailable, these rough guidelines can be used:

  • At 12 weeks, the uterus is just barely palpable above the pubic bone, using only an abdominal hand.
  • At 16 weeks, the top of the uterus is 1/2 way between the pubic bone and the umbilicus.
  • At 20-22 weeks, the top of the uterus is right at the umbilicus.
  • At full term, the top of the uterus is at the level of the ribs. (xyphoid process).

Ultrasound can be used to determine gestational age. Measurement of a crown-rump length during the first trimester (1-13 weeks) will give a gestational age that is usually accurate to within 3 days of the actual due date. During the second trimester (14-28 weeks), measurement of the biparietal diameter will accurately predict the due date within 10-14 days in most cases. In the third trimester, the accuracy of ultrasound in predicting the due date is less, with a plus or minus confidence range of as much as 3 weeks. A chart showing different ultrasound measurements at different gestational ages in shown in the Ultrasound Gestational Age Measurements chart.

Fetal Heart Beat

Although the fetal heart begins beating as early as the 5th week after the LMP, your ability to detect it will be limited by your equipment.

An ultrasound machine usually will see a heartbeat by 5 to 6 weeks gestation if equipped with a vaginal probe. Abdominal ultrasound will usually see the heartbeat by the 7th-8th week of pregnancy.

If you use a Doppler ultrasound fetal heartbeat detector, you can, with effort, usually hear the heartbeat by 12-14 weeks gestation and routinely after that.

Using a DeLee stethoscope (equipped with a head-mount), you can sometimes hear the heartbeat by 16 weeks but unless you are practiced with it, you won't hear it until 20 weeks, at which time the mother can usually tell you that she feels the baby moving.

Using a conventional stethoscope, you may never hear the fetal heartbeat.

Disability

Pregnancy causes many changes in women, not the least of which are change in weight and its' distribution, balance and increased vulnerability of ligaments and joints to stress. Because of these changes, the safe care of pregnant women requires that their normal work activities be modified. In the Navy, OPNAVINST 6000.1A is the instruction which provides the greatest detail of guidance for the administrative aspects of managing this disability. In the Marine Corps, MCO 5000.12d gives equivalent guidance.

Maternal Skin Changes

linea nigraOver time, there is a darkening of the maternal skin, in predictable ways.

  • Chloasma is a darkening of the facial skin, after the 16th week of pregnancy, particularly in women with darker complexions and significant exposure to the sun.. After delivery, the skin clears, but for some individuals, a persistent darkening of the skin remains.
  • Spider telangiectasias are small, bright red, star-shaped skin discolorations that blanch with direct compression and then return as soon as the compression is released. After delivery, they will largely resolve, but some may remain.
  • Stretch marks occur primarily in late pregnancy and are due to a separation of the underlying collagen tissue. They are dark red. After delivery, they will gradually lighten, ultimately healing as fine, faint, silvery-gray lines. Who gets them and how severe they are is dependent on the genetic predisposition of the mother and the degree of mechanical stress placed on the skin. There are no scientifically-established methods to either prevent them or treat them. However, generations of women have applied cocoa butter to the skin in the belief that it is helpful.
  • A "linea nigra" is a dark line running from the pubic bone up the center of the abdomen to the ribs. This appears late in pregnancy and is due to a combination of increasing concentration of melanocytes (skin cells capable of darkening) in that area, plus the high levels of melanocyte stimulating hormone produced by the placenta.

Exercise in Pregnancy

If the pregnancy is normal, moderate amounts of exercise are acceptable and desirable.

Some restrictions are appropriate:

1. Women should not start a new sport or exercise while pregnant, but may continue previous activities.

2. Activities which require a fine sense of balance to preserve the woman's personal safety (horseback riding, downhill skiing, etc.) are inadvisable  because pregnant women are inherently and unavoidably unstable in their balance.

3. Because of pregnancy-induced changes in the supporting cartilage and ligaments (softening), the joints are relatively unstable. Thus, activities which place great stress on any joints are unwise.

Nausea & Vomiting

These are common during pregnancy but may be aggravated by strong smells (food, garbage, machine oil, etc.) and motion. Symptoms appear quite early and are usually mild, requiring no treatment, disappearing by the 16th week or sooner. Occasionally, these symptoms are severe and require intervention.

If a pregnant woman states, "I can't keep anything down," and has ketones in her urine, she must be re-hydrated with crystalloid such as 5% dextrose in lactated Ringer's solution (D5LR). One liter is given in a short time (15-20 minutes), and the second liter given over an hour or two. Sometimes a third liter, given over several hours, will be necessary. While this rate of hydration would be much too fast for an older individual with heart disease, the cardiovascular system of a young, healthy, pregnant woman is very "stretchy" and will tolerate such rapid infusions well.

After IV therapy, the woman is generally feeling much better and can return to her duties. If this rehydration is insufficient to suppress her symptoms, then a more prolonged course of therapy is recommended.

Try to avoid antiemetics in the pregnant patient as the long-term consequences of most of the drugs on a developing pregnancy are not well established. Nonetheless, the long-term results of protracted vomiting, dehydration, electrolyte imbalance and ketosis are known and unfavorable to the pregnancy, so if it appears that IV hydration alone is not controlling the symptoms, move to antiemetics with dispatch.

Conventional doses of Antihistamines (Benadryl), Anticholinergics (Scopolamine), Compazine, Phenergan, and others have all been used to good advantage in these situations.

Heartburn

This common pregnancy-related ailment is caused by leaking of stomach acid into an unprotected esophagus, causing a chemical burn known as heartburn. The best relief is obtained by sucking on an antacid tablet until the pain goes away (one or two tablets).

Chewing and swallowing the tablets will also be effective but usually requires more tablets. If antacids are not available, eating or drinking anything will give some relief as it will partially buffer the acid in the esophagus and rinse it back down into the stomach.

Pepcid AC can also be used safely during pregnancy.

Sciatica

Sciatica occurs in 30% of pregnant women and is characterized by sharp pains in the hip and buttock on one or both sides, shooting down the back of the thigh. There may also be numbness of the anterior thigh on the effected side. This is due to compression of the sciatic nerve as it exits the spinal column in the small of the back. It is provoked by pregnancy and disappears after delivery.

Treatment of sciatica:

  • knees incorrectly positionedAvoid standing for long periods of time.
  • When sleeping, assume a semi-fetal position, with both knees drawn up and a pillow placed between the knees.
  • When sitting, make sure the knees are slightly flexed so that the knees are at least level with the hips or slightly higher than the hips.
  • Sleeping with one leg straight and the other knee drawn up is a bad position as far as the back is concerned. Torsion is placed on the lower spine, aggravating any pressure on the sciatic nerve that may be present.
  • knees properly positionedSleeping on the side while pregnant is a good, idea, but both knees should be drawn up (flexing the thighs). Either side will work well.
  • In order to maintain this semi-fetal position comfortably, it is necessary to place a small pillow, folded blanket or towel between the patient's knees. This will absorb moisture, separate the legs, minimizing skin-to-skin contact, and provide additional support to the legs. With practice, this position will become very comfortable.improper sitting posture

When sitting at a desk, posture is very important.

This picture illustrates two problems:

  • The chair is too high, resulting in her knees being lower than her hips.
  • She is not sitting straight toward the desk. This position places torsion on the lower back, aggravating her sciatica problem.

The lower picture has corrected one of the two problems.

  • proper sitting postureShe has lowered her chair and put a Chicago phone book underneath her feet, elevating them. This results in her knees being level with her hips, rocking her pelvis backwards and straightening out the lower spine. This will ease pressure on the sciatic nerve.
  • She has not turned to face the desk squarely. That would have solved the second problem.

Carpal Tunnel Syndrome

Approximately 30% of pregnant women will develop numbness in one or both hands following the distribution of the median nerve. (index finger, middle finger, medial surface of ring finger, with sparing of the lateral surface of the ring finger and the little finger).

Carpal TunnelThis is due to swelling and compression of the median nerve as it passes through the "carpal tunnel" in the wrist.

The dominant hand is more frequently effected. It is usually worse in the morning and improved in the evening. After delivery, the condition goes away gradually.

No treatment is necessary for this condition, so long as the motor portion of the nerve is still functioning normally. When treatment is necessary, splinting the wrist in a "cockup splint" will be helpful. Injection of the carpal tunnel with steroids may also be done (after 24 weeks of pregnancy).

Rarely, surgery may be necessary to free up the median nerve, although this is almost never required during pregnancy.

Upper Respiratory Infections

Most pregnant women will have at least one URI while pregnant.

Drugs are to be avoided, but the following medications may be used to good advantage if necessary:

Acetaminophen

 

This will effectively relieve muscle aches and fever. It is considered safe during pregnancy. (Category B drug, the same as prenatal vitamins.)

Guaifenesin

 

This expectorant is considered safe during pregnancy.

Pseudoephedrine

 

This sympathomimetic is a very effective decongestant. It's use during the 1st trimester is sometimes restricted because of indirect data suggesting a slight increased risk of fetal malformations. Late in the third trimester, its' use is again restricted because of its' somewhat unpredictable cardiovascular effects.

Triprolidine

An effective antihistamine, it is considered safe during pregnancy.

Antibiotics during Pregnancy

Because of various infections, the need to place pregnant women on antibiotics may arise. While this listing is necessarily incomplete due to space considerations, it will give you a guide to selecting antibiotics for these women.

Penicillins

Safe during pregnancy.

Cephalosporins

Safe during pregnancy.

Erythromycin

Safe during pregnancy.

Azithromycin

Safe during pregnancy.

Tetracycline(incl. doxy)

UNSAFE AT ANY TIME DURING PREGNANCY.

Metronidazole

Safe after 14 weeks. Avoid single-dose therapy. Safety prior to 14 weeks not well-established.

Aminoglycosides

Basically safe during pregnancy, but renal and ototoxicity are potential problems if the dose is high or prolonged.

Clindamycin

Safe during pregnancy.

Chloramphenicol

Probably safe prior to 28 weeks

Sulfa drugs

Safe prior to 34 weeks. After that, babies may develop jaundice if exposed to sulfa.

Quinine

Only to be used in life-threatening, chloroquine-resistant P. Falciparum infections

Miconazole

Safe during pregnancy.

Clotrimazole

Safe during pregnancy.

Quinacrine

Probably safe during pregnancy.

Chloroquine

With prolonged or high doses may cause congenital defects.

Pyrimethamine

Safe after 1st trimester. Add folic acid supplement.

Trimethoprim

Safe after 1st trimester. Add folic acid supplement.

Primaquine

May cause hemolytic anemia in the presence of G6PD deficiency. You may use it if needed.

 

Other Drugs during Pregnancy

Local anesthetics (Xylocaine) may be used with safety, although the addition of epinephrine to them is problematic. Epinephrine may have unpredictable effects on the maternal cardiovascular system (and hence the blood flow to the baby), so epinephrine is generally to be avoided.

Aspirin should not be taken as it may lead to significant fetal hemorrhage.

Codeine, Demerol, Morphine and other narcotics may be used as needed at any stage of pregnancy, but the addictive potential should be recognized. Other than the risk of fetal drug withdrawal syndrome, these major pain relievers are considered safe for use during pregnancy.

Immunization during Pregnancy

 

 

 

Tetanus Booster

Safe during pregnancy.

Diphtheria Toxoid

Safe during pregnancy.

Hepatitis B vaccine

May be safely given to pregnant women who are at high risk of exposure.

Influenza or pneumococcal immunization

May be given to pregnant women if they are at increased risk of these conditions.

Measles, mumps and rubella vaccine

Do not give to a woman while pregnant but defer until after the pregnancy.

Yellow Fever

Can and should be given to pregnant women traveling to areas where Yellow Fever endemic.

Polio

Can and should be given to pregnant women traveling to areas where polio is endemic.

Anthrax Immunization

Do not administer during pregnancy.

Immune globulin

May be given any time it is clinically indicated.

Thermal Stress

Fetal enzyme systems may not function properly if subjected to unusually high temperatures. In laboratory animals, elevation of core temperature is associated with fetal losses. For this reason, pregnant women are generally restricted from saunas and Jacuzzis.

The important thing to avoid is elevation of the core temperature. Any activity which may lead to an elevation of core temperature should be restricted. This would include sedentary exposure to high ambient temperatures which would otherwise be tolerated by a non-pregnant person, or moderate exercise in moderately-elevated temperatures.

Aboard warships, high ambient temperatures are often found in the:

  • Engine spaces
  • Laundry
  • Mess decks

Noise

Pregnant women should wear hearing protection when exposed to ambient noise levels above 84dBA, including infrequent impact noise. (So should non-pregnant women and men.)

Brief exposure (5 minutes per hour or less) of hearing-protected pregnant women to ambient noise above 84dBA in order to transit high noise areas is probably safe. Prolonged exposure to this level of noise is not recommended.

Pregnant women should avoid any exposure to ambient noise greater than 104dBA (corresponding to the need for double hearing protection), unless absolutely essential for quickly moving through a high noise area.

The abdominal wall muffles (attenuates) the noise only somewhat and these very noisy areas may pose significant problems for the developing fetus.

Low-Frequency Whole Body Vibration

This is the type of shaking vibration one might experience if operating a jackhammer or driving at high speed over a highway with many potholes. It is to be avoided during pregnancy.

Chemical Solvents

Organic solvents, such as turpentine, fuel, oils, lubricants, and paint thinner may have adverse effects on a developing fetus.

The greatest risk comes from ingestion of these solvents, or by chemical spills with contamination of the skin. Inhalation, though less likely to delivery significant quantities of the material, should also be avoided.

Heavy Metals

It is very important to avoid maternal exposure to lead, cadmium and mercury.

X-rays during Pregnancy

All things being equal (which they never are), it is better to avoid x-rays while pregnant.

If indicated, (chronic cough, possible fracture, etc.), then x-rays are acceptable.

If you need an x-ray for a pregnant patient, go ahead and get it, but try to shield the baby with a lead apron to minimize the fetal exposure.

In your zeal to shield the pregnant abdomen, be careful not to shield so much that the value of the x-ray is diminished. If the shielding is too high while obtaining a chest x-ray, you will have to obtain a second x-ray to visualize the area shielded during the first x-ray.

Radiation exposure during Pregnancy

There appears to be a threshold for fetal malformation or death of at least 10 Rads, below which, biologic effects cannot be demonstrated. Allowing for a 10-fold margin of safety, it does not appear that any exposure below 1 Rad will have any harmful effects.

It would take about a thousand chest x-rays to deliver this amount of radiation to the unshielded maternal pelvis. 

At the same time, our knowledge of the biologic effects or radiation may be incomplete, so it is better for pregnant women, as a rule, to avoid any unnecessary exposure to ionizing radiation, and to use appropriate shielding when it is necessary.

CRT Use and Pregnancy

There is no good evidence that working in front of a CRT (Cathode Ray Tube) poses any threat for the pregnant woman, either from electromagnetic radiation (EMR) or from eyestrain.

Ergonomics are important for all sitting personnel, and particularly pregnant women. Good low back support, correct height for the CRT, wrist support and proper positioning of the legs (with the thighs flexed slightly so the knees are at least level with the hips, if not slightly higher than the hips), will contribute to the comfort and performance of these personnel.

Diving while Pregnant

Simply stated, pregnant women should not dive. It poses health risks to themselves and their fetus.

Pregnant women have increased amounts of body fat and 3rd-space fluid retention, each of which tends to trap nitrogen and other gasses due to poor circulation through those areas. This predisposes them to decompression sickness and air embolism.

While fetuses do not form gas bubbles more easily than women, even a few bubbles are likely to be very dangerous to the fetus because of fetal circulation. In adults, bubbles tend to be filtered by the pulmonary circulation through the lungs, but in fetuses, there is a bypass of the lung circulation through the foramen ovale and ductus arteriosus. This means that bubbles will not be filtered but may instead go directly to the brain or coronary vessels, possibly causing stroke or death.

There is also evidence that diving may produce birth defects, including limb reductions, cardiac malformations, and other problems, although this area has not been carefully researched.

Hyperbaric treatment

The effects of controlled hyperbarism on pregnant women and fetal development are uncertain.

In eastern Europe, scientists using relatively low pressures but repeatedly and for long periods of time have reported no particular problems with it. One study suggests that while in a hyperbaric atmosphere, the fetus changes its' circulatory flow in the direction of neonatal flow patterns (with narrowed or closed ductus arteriosus and foramen ovale). Upon return to normal barostatus, the flow again reverses to the normal fetal flow pattern. Whether this change poses any long-term problems for the fetus is unknown.

Based on these concerns, it is inadvisable to allow any pregnant woman to dive or enter a hyperbaric chamber unless strongly indicated for medical reasons. If an accident occurs in which it would be desirable to place the pregnant woman in a hyperbaric chamber, the risks to the fetus (mainly theoretical) must be balanced against the risks to the mother of not undergoing hyperbaric treatment.

Pregnant Aircrew Members

Aircrew status while pregnant is a complex issue, involving fetal risks, maternal risks and aircrew performance.

The maternal risks include decreased balance, decreased motion tolerance, decreased g-tolerance, gas compression/recompression effects. During the second and third trimester, placental abruption caused by the shearing force of inadvertently falling or striking the abdomen violently is a relatively common occurrence.

Fetal risks include exposure to noise, heat, chemicals, organic solvents, and low-frequency, whole-body vibration.

For these reasons, there is general agreement among the services to restrict pregnant aircrewman from participating in high-performance aircraft flights. There is less agreement in the area of helicopters and multiengine, fixed-wing aircraft.

Whether to allow a pregnant aircrewmember to continue her flight duties should be individualized, after considering the stage of pregnancy, the presence or absence of risk factors for her pregnancy or her flight crew performance, her individual service's rules, the degree of exposure to potentially harmful stressors in the aviation environment.

*These videos are an added feature, provided by the Brookside Associates Medical Education Division. They were not present in the original edition.


Home    Introduction    Medical Support of Women in Field Environments    The Prisoner of War Experience    Routine Care    Pap Smears    Human Papilloma Virus    Contraception    Birth Control Pills    Vulvar Disease    Vaginal Discharge    Abnormal Bleeding    Menstrual Problems    Abdominal Pain    Urination Problems    Menopause    Breast Problems    Sexual Assault    Normal Pregnancy    Abnormal Pregnancy    Normal Labor and Delivery    Problems During Labor and Delivery    Care of the Newborn

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Operational Obstetrics & Gynecology - 2nd Edition
The Health Care of Women in Military Settings
CAPT Michael John Hughey, MC, USNR
NAVMEDPUB 6300-2C
January 1, 2000

This web version of Operational Obstetrics & Gynecology is provided by The Brookside Associates Medical Education Division.  It contains original contents from the official US Navy NAVMEDPUB 6300-2C, but has been reformatted for web access and includes advertising and links that were not present in the original version. This web version has not been approved by the Department of the Navy or the Department of Defense. The presence of any advertising on these pages does not constitute an endorsement of that product or service by either the Department of Defense or the Brookside Associates. The Brookside Associates is a private organization, not affiliated with the United States Department of Defense. All material in this version is unclassified.

This formatting 2006 Medical Education Division, Brookside Associates, Ltd.
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