OI Issues:
Pregnancy

 

A woman with osteogenesis imperfecta (OI) who becomes pregnant may experience an uneventful pregnancy or one that is laden with difficulties. Similarly, a developing fetus that is found to have OI may be born with very few complications, or it may not survive beyond a few hours. It is estimated that a woman with OI who becomes pregnant represents only 1 in 25,000 pregnancies that occur. Because OI is rare, and a pregnant woman with OI is even more rare, most obstetricians and other medical care providers will not have had experience in managing such cases.

There is little data available at present about the likelihood of a woman with OI developing certain complications during pregnancy. The lack of consistency in reporting the various physical and laboratory findings, combined with the wide variance in severity among people with OI, makes it difficult to draw any clear conclusions regarding a possible relationship between OI and many of the complications that have been reported thus far. However, this fact sheet will attempt to address some of the specific problems that have been suggested to be associated with OI during pregnancy.

Obstetric and Gynecologic Concerns of Women with OI
Women with OI can expect to begin menstruating at the same age as women who do not have OI. Menstrual periods usually occur at the customary time and cycles are generally regular. There may be heavy bleeding in women with a history of easy bruising or bleeding tendencies. While reproduction may be hampered due to increased susceptibility to fractures or limited hip movement, there is no evidence to suggest that fertility or miscarriage rates are influenced by OI.

Pregnancy does not appear to have a significant adverse effect on the milder forms of the disorder. Women with OI Types I and IV may experience loose joints, reduced mobility, increased bone pain and dental problems during pregnancy. In general, the medical concerns prior to pregnancy in these women will be limited.

Individuals with the more severe and debilitating forms of OI who have short stature and curvature of the spine may be at increased risk for both medical and obstetrical complications. If the level of curvature of the spine is great, the likelihood of heart and lung difficulties is increased. It is possible that these women will require early hospitalization due to increasing breathlessness. Premature delivery or even termination of a pregnancy may be necessary if signs of severe heart and lung problems develop. As the uterus grows, the shortened distance between the thoracic cage and the pubic bone can cause discomfort and result in a need for extended bedrest.

Various obstetrical complications have been reported in women with OI, including pre-eclampsia (which is characterized by high blood pressure, protein in the urine, and body swelling), premature delivery, placenta previa (when the placenta becomes implanted in the uterus and covers the cervix opening), premature rupture of membranes, recurrent urinary tract infections, anemia (low red blood cell count), and calcium deficiency. However, based on the available information, it does not appear that there is a strong association between OI and these events. Another way to consider this concept is just because people with OI routinely catch a cold, we do not conclude that there is any association between OI and the common cold.

Pregnancy has not been associated with an increased risk of maternal fractures. However, trauma during pregnancy or obstetrical manipulation at the time of vaginal delivery may result in fractures. It has been suggested that because a risk does exist for a woman with OI to fracture during delivery and because there is potential for other complications, elective caesarean section may be the delivery method of choice for most women with OI. Some of the reported complications during delivery include: (1) a birth canal that is too small to permit birth, (2) uterine rupture, and (3) hemorrhaging. Some physicians might consider a caesarean section prudent if there is a history of previous pelvic fractures or contracted pelvis, or if the woman has a severe form of OI. However, in women with OI who have normal pelvic dimensions, there does not appear to be a compelling reason to avoid labor or vaginal delivery.

Bleeding disorders in OI are usually not a problem. In those cases reported to have excessive bleeding following delivery, each had some form of prior trauma during labor. Since blood coagulation and platelet parameters were normal in these cases, it was suspected that the hemorrhage was due to the inability of the tissue to heal properly from the collagen defect found in OI. Women at greatest risk for bleeding would be those with a history of recurrent nosebleeds, easy bruising, or excessive bleeding following previous orthopedic procedures.

In the absence of clear indication of who may be at greatest risk for hyperthermia (an increase in body temperature during anesthesia), some physicians might consider spinal or epidural anesthesia to be the safest approach. These anesthesia procedures, which involve injection of medication near the spine, may be difficult in some women with deformity from vertebral compression fractures.

When either parent is affected with OI, the fetus is at risk of being born with OI as well. In this circumstance, there is, in fact, a 50% chance in each pregnancy that the fetus will also have OI. Excluding OI, the risk of other congenital disorders resulting from pregnancies where one parent has OI is no greater than that of the general population.

Obstetric Consideration for Unaffected Women When OI is Detected in the Fetus
Sometimes, through routine ultrasound, OI is suspected in the fetus of an unaffected mother. The ultrasound may have been ordered because of a previously affected pregnancy; however, the majority of cases are in women with no previous history of OI. In either situation, the finding presents certain medical and ethical questions to be addressed in order to direct the remainder of the prenatal care, including accuracy of the diagnosis, severity of the disorder, prognosis for survival and development, and mode of delivery.

The age of the fetus when the ultrasound is performed is important to achieve an accurate diagnosis and to provide the parents with the necessary information to consider all options for the remainder of the pregnancy. In pregnancies where OI Type II is suspected, the studies performed prior to 24 weeks gestation will very likely detect the severe shortening of the long bones and innumerable fractures in the limbs and thoracic cage. Fetuses with Type III OI are often detectable early in the second trimester due to the presence of multiple fractures and shortened limbs. When faced with these findings, couples are typically advised that Type II OI is lethal and that Type III is often associated with significant disability and at times early mortality. It must also be realized that cases have been reported where the presumption that the infant would not survive was discredited by children with severe forms of OI surviving and living fulfilling and productive lives. While bowing of the long bones may be present in the second trimester, fractures in Types I and IV OI may not be seen until the third trimester, if at all.

With regard to mode of delivery, it has been suggested that caesarean section would be less traumatic than vaginal delivery when fractures of the long bones of a fetus with Types I, III, or IV OI are identified. However, there are no data to confirm that this assumption is correct. Theoretically, there is an increased risk of central nervous system injury with vaginal delivery when the baby's skull is poorly mineralized.

Therefore, many physicians feel it would be appropriate, when planning a mode of delivery, to assess the degree of mineralization in the baby's skull. Due to the grim prognosis in Type II OI, the risk-benefit ratio of elective caesarean is discussed with the patient.

Genetic Counseling
Ideally, couples at risk because of parental or previous fetal OI should be seen for counseling prior to conception. Couples should be made aware of various complications that can be associated with OI and pregnancy. Discussion would include the availability of various prenatal diagnosis techniques following chorionic villus sampling, amniocentesis, or second trimester antenatal ultrasound for the detection of OI. Weekly ultrasounds after 36 weeks gestation may be beneficial in detecting skeletal changes that may preclude vaginal delivery. Intrauterine pressure catheters and fetal scalp monitoring can be considered with vaginal deliveries due to the possibility of uterine rupture during labor.

While there are obviously increased maternal and fetal risks for women with OI, the majority of women with OI who successfully conceive seem to go through pregnancy quite well.

This information is reprinted, with modifications, from Johnson, A. (1994). Pregnancy and osteogenesis imperfecta. In Heidi Glauser, (Ed.), Living with Osteogenesis Imperfecta: A guidebook for families (pp. 23-32). Tampa, FL: Osteogenesis Imperfecta foundation, Inc.


This information is brought to you by the
NIH Osteoporosis and Related Bone Diseases~National Resource Center (ORBD~NRC)
and the Osteogenesis Imperfecta Foundation

National Institutes of Health
 Osteoporosis and Related Bone Diseases
 National Resource Center
1232 22nd St., NW
Washington, DC 20037-1292
Tel: 800/624-BONE or 202/223-0344
Fax: 202/293-2356, TYY: 202/466-4315
http://www.osteo.org
E-mail: orbdnrc@nof.org

The National Resource Center is supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases with contributions from the National Institute of Child Health and Human Development, National Institute of Dental and Craniofacial Research, National Institute of Environmental Health Sciences, NIH Office of Research on Women's Health, Office of Women's Health, PHS, and the National Institute on Aging. The Resource Center is operated by the National Osteoporosis Foundation, in collaboration with the Paget Foundation and the Osteogenesis Imperfecta Foundation.


12/97
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