Some risk factors are present before women become pregnant. These risk factors include
Problems in a previous pregnancy Problems in a Previous Pregnancy Some risk factors are present before women become pregnant. These risk factors include Certain physical characteristics, such as age and weight Problems in a previous pregnancy, including the... read more
, including the need to have a cesarean delivery Cesarean Delivery Cesarean delivery is surgical delivery of a baby by incision through a woman’s abdomen and uterus. In the United States, up to 30% of deliveries are cesarean. Doctors use a cesarean delivery... read more 
Other problems that increase risk can develop during pregnancy or during labor and delivery Introduction to Complications of Labor and Delivery Usually, labor and delivery occur without any problems. Serious problems are relatively rare, and most can be anticipated and treated effectively. However, problems sometimes develop suddenly... read more .
Needing to have surgery Disorders That Require Surgery During Pregnancy During pregnancy, a disorder that requires surgery may develop. Major surgery, particularly if it involves the abdomen, increases the risk of preterm labor and can cause a miscarriage, especially... read more , particularly abdominal surgery, during pregnancy increases the risk of preterm labor Preterm Labor Labor that occurs before 37 weeks of pregnancy is considered preterm. Babies born prematurely can have serious health problems. The diagnosis of preterm labor is usually obvious. Measures such... read more and miscarriages Miscarriage A miscarriage is the loss of a fetus before 20 weeks of pregnancy. Miscarriages may occur because of a problem in the fetus (such as a genetic disorder or birth defect) or in the woman (such... read more , especially early in pregnancy. Thus, surgery is usually delayed if possible. However, if necessary, surgery should proceed without delay and is still usually reasonably safe.
Physical Characteristics
The following characteristics of women affect risk during pregnancy.
Age
About 13% of all pregnancies occur in adolescents. Adolescents are at increased risk of having the following:
Preeclampsia Preeclampsia and Eclampsia Preeclampsia is new high blood pressure or worsening of existing high blood pressure that is accompanied by excess protein in the urine and that develops after the 20th week of pregnancy. Eclampsia... read more (a type of high blood pressure that develops during pregnancy)
Adolescents can have babies who are born underweight (small-for-gestational age Small-for-Gestational-Age (SGA) Newborns A newborn who weighs less than 90% of newborns of the same gestational age at birth (below the 10th percentile) is considered small for gestational age. Newborns may be small because their parents... read more ).
Part of the reason for these risks is that adolescents are less likely to get medical care during pregnancy. Thus, they may not understand what activities and behaviors (such as smoking, drinking alcohol, and having sex without using a condom) can put their pregnancy at risk. Many adolescents smoke. They also have a higher risk of getting a sexually transmitted infection Overview of Sexually Transmitted Infections (STIs) Sexually transmitted infection (STI) refers to an infection that is passed through blood, semen, vaginal fluids, or other body fluids during oral, anal, or genital sex with an infected partner... read more 
. Using condoms can help prevent sexually transmitted infections.
Women aged 35 and older are at increased risk of having the following:
A preexisting disorder that increases risk during pregnancy, such as high blood pressure High Blood Pressure During Pregnancy High blood pressure (hypertension) during pregnancy is classified as one of the following: Chronic hypertension: Blood pressure was high before the pregnancy. Gestational hypertension: Blood... read more or diabetes Diabetes During Pregnancy For women who have diabetes before they become pregnant, the risks of complications during pregnancy depend on how long diabetes has been present and whether complications of diabetes, such... read more
Problems related to the pregnancy, such as preeclampsia Preeclampsia and Eclampsia Preeclampsia is new high blood pressure or worsening of existing high blood pressure that is accompanied by excess protein in the urine and that develops after the 20th week of pregnancy. Eclampsia... read more , gestational diabetes Gestational diabetes For women who have diabetes before they become pregnant, the risks of complications during pregnancy depend on how long diabetes has been present and whether complications of diabetes, such... read more (diabetes that develops during pregnancy), chromosomal abnormalities Overview of Chromosome and Gene Disorders Chromosomes are structures within cells that contain a person's genes. A gene is a segment of deoxyribonucleic acid ( DNA) and contains the code for a specific protein that functions in one... read more in the fetus, and stillbirth Stillbirth Stillbirth is death of a fetus after 20 weeks of pregnancy. Stillbirth may result from a problem in the woman, placenta, or fetus. Doctors do blood tests to try to identify the cause of a stillbirth... read more
Complications during labor, such as difficult labor or a placenta that detaches too soon (placental abruption Placental Abruption Placental abruption is the premature detachment of the placenta from the wall of the uterus, usually after 20 weeks of pregnancy. Women may have abdominal pain and tenderness and vaginal bleeding... read more ) or is mislocated (placenta previa Placenta Previa Placenta previa is attachment (implantation) of the placenta over the opening of the cervix, in the lower rather than the upper part of the uterus. Women may have painless, sometimes profuse... read more
)
Children of women aged 35 or older are more likely to have birth defects, such as heart defects Overview of Heart Defects About one in 100 babies is born with a heart defect. Some are severe, but many are not. Defects may involve abnormal formation of the heart's walls or valves or of the blood vessels that enter... read more . a narrowed esophagus (esophageal atresia Esophageal Atresia and Tracheoesophageal Fistula Esophageal atresia is a birth defect in which the esophagus narrows or comes to an end. Most newborns with esophageal atresia also have an abnormal connection between the esophagus and the windpipe... read more ), a defect of the urethra called hypospadias Hypospadias Birth defects of the genitals can involve the penis, scrotum, or testes (testicles) in boys and the vagina and labia in girls. Sometimes the genitals are ambiguous, that is, not clearly female... read more 
, or a defect of the skull called craniosynostosis Craniosynostosis Craniosynostosis is a birth defect in which one or more of the skull's sutures close too early. Birth defects, also called congenital anomalies, are physical abnormalities that occur before... read more 
.
As women age, genetic evaluation Genetic Screening Before Pregnancy Genetic screening is used to determine whether a couple is at increased risk of having a baby with a hereditary genetic disorder. Hereditary genetic disorders are disorders of chromosomes or... read more for chromosomal abnormalities becomes more important. In older pregnant women, ultrasonography may be done to help determine whether the fetus has birth defects,
Weight
Women who are very thin—with a body mass index (BMI) of less than 19.8 (see table Determining Body Mass Index Osteonecrosis of the Jaw Osteonecrosis is the death of bone cells. Osteonecrosis of the jaw is the death of some cells in your jawbone. Osteonecrosis of the jaw can happen on its own or after you have a tooth pulled... read more )—or weigh less than 100 pounds before becoming pregnant are more likely to have
Small, underweight babies
Overweight women (with a BMI of 25 to 29.9 before pregnancy) and obese women (with a BMI of more than 30) are more likely to have the following problems:
Very large babies (large-for-gestational age Large-for-Gestational-Age (LGA) Newborns A newborn who weighs more than 90% of newborns of the same gestational age at birth (above the 90th percentile) is considered large for gestational age. Newborns may be large because the parents... read more ), which may be difficult to deliver
Babies who are born underweight (small-for-gestational age Small-for-Gestational-Age (SGA) Newborns A newborn who weighs less than 90% of newborns of the same gestational age at birth (below the 10th percentile) is considered small for gestational age. Newborns may be small because their parents... read more )
Miscarriages Miscarriage A miscarriage is the loss of a fetus before 20 weeks of pregnancy. Miscarriages may occur because of a problem in the fetus (such as a genetic disorder or birth defect) or in the woman (such... read more and stillbirth Stillbirth Stillbirth is death of a fetus after 20 weeks of pregnancy. Stillbirth may result from a problem in the woman, placenta, or fetus. Doctors do blood tests to try to identify the cause of a stillbirth... read more
Gestational hypertension High Blood Pressure During Pregnancy High blood pressure (hypertension) during pregnancy is classified as one of the following: Chronic hypertension: Blood pressure was high before the pregnancy. Gestational hypertension: Blood... read more (high blood pressure that first develops after 20 weeks of pregnancy)
Preeclampsia Preeclampsia and Eclampsia Preeclampsia is new high blood pressure or worsening of existing high blood pressure that is accompanied by excess protein in the urine and that develops after the 20th week of pregnancy. Eclampsia... read more (gestational hypertension accompanied by protein in the urine)
A pregnancy that lasts 42 weeks or longer (postterm pregnancy Postterm Pregnancy and Postmaturity A postterm pregnancy is one that lasts 42 weeks or more. In postmaturity, the placenta can no longer maintain a healthy environment for the fetus because the pregnancy has lasted too long. On... read more )
Doctors encourage overweight and obese women to exercise at least 3 times a week for a total of 150 minutes a week. These women should talk to their doctor about what exercises are appropriate for them. Changes to a healthier diet may be recommended.
Height
Women shorter than 5 feet are more likely to have a small pelvis, which may make movement of the fetus through the pelvis and vagina (birth canal) difficult during labor. For example, the fetus's shoulder is more likely to lodge against the pubic bone. This complication is called shoulder dystocia Shoulder Dystocia Position refers to whether the fetus is facing rearward (toward the woman’s back—that is, face down when the woman lies on her back) or forward (face up). It’s important to check the baby’s... read more . Also, short women are more likely to have preterm labor Preterm Labor Labor that occurs before 37 weeks of pregnancy is considered preterm. Babies born prematurely can have serious health problems. The diagnosis of preterm labor is usually obvious. Measures such... read more and a baby who is born underweight (small-for-gestational age Small-for-Gestational-Age (SGA) Newborns A newborn who weighs less than 90% of newborns of the same gestational age at birth (below the 10th percentile) is considered small for gestational age. Newborns may be small because their parents... read more ).
Reproductive abnormalities
Structural abnormalities in the uterus or cervix increase the risk of the following:
A difficult labor
Preterm labor Preterm Labor Labor that occurs before 37 weeks of pregnancy is considered preterm. Babies born prematurely can have serious health problems. The diagnosis of preterm labor is usually obvious. Measures such... read more or a premature baby Preterm (Premature) Newborns A preterm newborn is a baby delivered before 37 weeks of gestation. Depending on when they are born, preterm newborns have underdeveloped organs, which may not be ready to function outside of... read more
Structural abnormalities include a double uterus, fibroids Uterine Fibroids A fibroid is a noncancerous tumor of the uterus that is composed of muscle and fibrous tissue. Uterine fibroids are very common, occurring in approximately 70% of White women and 80% of Black... read more 
in the uterus, and a weak (incompetent) cervix (cervical insufficiency Cervical Insufficiency Cervical insufficiency is painless opening of the cervix that results in delivery of the baby during the 2nd trimester of pregnancy. Connective tissue disorders that are present at birth and... read more 
) that tends to open (dilate) as the fetus grows. Fibroids occasionally cause the placenta to be mislocated (called placenta previa Placenta Previa Placenta previa is attachment (implantation) of the placenta over the opening of the cervix, in the lower rather than the upper part of the uterus. Women may have painless, sometimes profuse... read more ), labor to begin too early (preterm labor Preterm Labor Labor that occurs before 37 weeks of pregnancy is considered preterm. Babies born prematurely can have serious health problems. The diagnosis of preterm labor is usually obvious. Measures such... read more ), and miscarriages to occur. Cervical insufficiency increases the risk that a baby will be delivered too soon (preterm delivery).
Problems in a Previous Pregnancy
Women who have had a problem in one pregnancy are more likely to have a problem, often the same one, in subsequent pregnancies. Such problems include having had any of the following:
A baby that weighed more than 10 pounds (large-for-gestational age Large-for-Gestational-Age (LGA) Newborns A newborn who weighs more than 90% of newborns of the same gestational age at birth (above the 90th percentile) is considered large for gestational age. Newborns may be large because the parents... read more )
A history of several pregnancy losses
Rh incompatibility Hemolytic Disease of the Fetus and Newborn Rh incompatibility occurs when a pregnant woman has Rh-negative blood and the fetus has Rh-positive blood. Rh incompatibility can result in destruction of the fetus’s red blood cells, sometimes... read more that required a blood transfusion to the fetus
A fetus in an abnormal position Abnormal Position and Presentation of the Fetus Position refers to whether the fetus is facing rearward (toward the woman’s back—that is, face down when the woman lies on her back) or forward (face up). It’s important to check the baby’s... read more , such as buttocks first (breech)
A baby with an injury Nerve injuries Birth injury is damage that occurs as a result of physical pressure during the birthing process, usually during transit through the birth canal. Many newborns have minor injuries during birth... read more
that stretched the nerves in the baby's shoulder (brachial plexus injury) during delivery
Women may have a condition that tends to make the same problem recur. For example, women with diabetes are more likely to have babies that weigh more than 10 pounds at birth.
Women who had a baby with a genetic disorder or birth defect are more likely to have another baby with a similar problem. Genetic testing Genetic Screening Before Pregnancy Genetic screening is used to determine whether a couple is at increased risk of having a baby with a hereditary genetic disorder. Hereditary genetic disorders are disorders of chromosomes or... read more of the baby, even if stillborn, and of both parents may be appropriate before another pregnancy is attempted. If these women become pregnant again, tests such as high-resolution ultrasonography Ultrasonography Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more , chorionic villus sampling Chorionic Villus Sampling Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more , and amniocentesis Amniocentesis Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more may help determine whether the fetus has a genetic disorder or birth defect. These women may be referred to a specialist.
Having had five or more pregnancies increases the risk of very rapid labor and excessive bleeding after delivery.
Having had twins or more fetuses in one pregnancy increases the risk of the following:
Underweight babies
Birth defects
Stillbirth or death of the newborn
Disorders Present Before Pregnancy
Before becoming pregnant, women may have a disorder that can increase the risk of problems during pregnancy. These disorders include
Problems with the fallopian tubes Infertility Problems With the Fallopian Tubes and Abnormalities in the Pelvis If a fallopian tube is blocked or damaged, women may have fertility problems. A blocked or damaged fallopian tube can prevent the sperm from reaching the egg or prevent the egg or fertilized... read more
Women who have one of these disorders should talk with a doctor and try to get in the best physical condition possible before they become pregnant. After they become pregnant, they may need special care, often from an interdisciplinary team. The team may include an obstetrician (who may also be a specialist in the disorder), a specialist in the disorder, and other health care practitioners (such as nutritionists).
Disorders During Pregnancy
During pregnancy, a problem may occur or a disorder may develop to make the pregnancy high risk.
Some disorders that occur during pregnancy are related to (are complications of) pregnancy. Other disorders are not directly related to pregnancy (see Pregnancy Complicated by Disease Overview of Disease During Pregnancy During pregnancy, having a disorder can increase the risk of problems. The disorder may be one that Women had before they became pregnant (preexisting disorders) Develops during the pregnancy... read more ). Certain disorders are more likely to occur during pregnancy because of the many changes pregnancy causes in a woman's body.
Pregnancy complications are problems that occur during pregnancy. They may affect the woman, the fetus, or both and may occur at different times during the pregnancy. For example, complications such as a mislocated placenta (placenta previa Placenta Previa Placenta previa is attachment (implantation) of the placenta over the opening of the cervix, in the lower rather than the upper part of the uterus. Women may have painless, sometimes profuse... read more ) or premature detachment of the placenta from the uterus (placental abruption Placental Abruption Placental abruption is the premature detachment of the placenta from the wall of the uterus, usually after 20 weeks of pregnancy. Women may have abdominal pain and tenderness and vaginal bleeding... read more ) can cause bleeding from the vagina during pregnancy Vaginal Bleeding During Late Pregnancy During late pregnancy (after 20 weeks), 3 to 4% of women have vaginal bleeding. Bleeding may be a signal that there is a risk of losing the baby or of bleeding excessively (hemorrhaging). In... read more . Women who have heavy bleeding are at risk of losing the baby or of going into shock and, if not promptly treated, of dying during labor and delivery.
Other pregnancy complications include
Problems with amniotic fluid Problems With Amniotic Fluid Amniotic fluid is the fluid that surrounds the fetus in the uterus. The fluid and fetus are contained in membranes called the amniotic sac. Problems with amniotic fluid include Too much amniotic... read more (the fluid that surrounds the fetus in the uterus)
A weak cervix (cervical insufficiency Cervical Insufficiency Cervical insufficiency is painless opening of the cervix that results in delivery of the baby during the 2nd trimester of pregnancy. Connective tissue disorders that are present at birth and... read more
) that tends to open (dilate) as the fetus growsAn infection of the tissues around the fetus, such as the amniotic fluid (intra-amniotic infection Intraamniotic Infection Intraamniotic infection is infection of the tissues around the fetus, such as the fluid that surrounds the fetus (amniotic fluid), the placenta, the membranes around the fetus, or a combination... read more )
A previous miscarriage Miscarriage A miscarriage is the loss of a fetus before 20 weeks of pregnancy. Miscarriages may occur because of a problem in the fetus (such as a genetic disorder or birth defect) or in the woman (such... read more or stillbirth Stillbirth Stillbirth is death of a fetus after 20 weeks of pregnancy. Stillbirth may result from a problem in the woman, placenta, or fetus. Doctors do blood tests to try to identify the cause of a stillbirth... read more
Preeclampsia Preeclampsia and Eclampsia Preeclampsia is new high blood pressure or worsening of existing high blood pressure that is accompanied by excess protein in the urine and that develops after the 20th week of pregnancy. Eclampsia... read more (a type of high blood pressure that develops during pregnancy)
Rh incompatibility Hemolytic Disease of the Fetus and Newborn Rh incompatibility occurs when a pregnant woman has Rh-negative blood and the fetus has Rh-positive blood. Rh incompatibility can result in destruction of the fetus’s red blood cells, sometimes... read more (when a pregnant woman has Rh-negative blood and the fetus has Rh-positive blood)
Exposures During Pregnancy
During pregnancy, being exposed to the following can increase the risk of having a baby with a birth defect:
Certain infections
Certain drugs Drug Use During Pregnancy More than 50% of pregnant women take prescription or nonprescription (over-the-counter) drugs or use social drugs (such as tobacco and alcohol) or illicit drugs at some time during pregnancy... read more (such lithium, azithromycin, erythromycin, and antidepressants called selective serotonin reuptake inhibitors)
Radiation Radiation and children Radiation injury is damage to tissues caused by exposure to ionizing radiation. Large doses of ionizing radiation can cause acute illness by reducing the production of blood cells and damaging... read more and certain chemicals (such as carbon monoxide Lead Poisoning Lead poisoning affects many parts of the body, including the brain, nerves, kidneys, liver, and blood. Children are particularly susceptible because their nervous system is still developing... read more , lead Lead Poisoning Lead poisoning affects many parts of the body, including the brain, nerves, kidneys, liver, and blood. Children are particularly susceptible because their nervous system is still developing... read more , gasoline Hydrocarbon Poisoning
, and mercury Mercury in seafood Some risk factors are present before women become pregnant. These risk factors include Certain physical characteristics, such as age and weight Problems in a previous pregnancy, including the... read more )
These substances and conditions are called teratogens.
Birth defects Overview of Birth Defects Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. They are usually obvious within the first year of life. The cause of many birth... read more are most likely to result if women are exposed to a teratogen 2 to 8 weeks after they become pregnant (4 to 10 weeks after their last menstrual period) because the fetus's organs are forming during this time. The risk of having a miscarriage Miscarriage A miscarriage is the loss of a fetus before 20 weeks of pregnancy. Miscarriages may occur because of a problem in the fetus (such as a genetic disorder or birth defect) or in the woman (such... read more is also increased.
Infections that are particularly dangerous during pregnancy include
Infections with cytomegalovirus Cytomegalovirus (CMV) Infection Cytomegalovirus infection is a common herpesvirus infection with a wide range of symptoms: from no symptoms to fever and fatigue (resembling infectious mononucleosis) to severe symptoms involving... read more , coxsackievirus, or parvovirus B19 Erythema Infectiosum (Parvovirus B19 Infection) Erythema infectiosum is a contagious viral infection. In children, it causes a blotchy or raised red rash on areas of the body and a slapped-cheek red rash on the face along with mild illness... read more
Drugs that may increase the risk of birth defects include
Some prescription drugs (see table Some Drugs That Can Cause Problems During Pregnancy Some Drugs That Can Cause Problems During Pregnancy*
)
Exposure to high temperatures (for example, in a sauna) during the 1st trimester has been linked to the development of spina bifida Neural Tube Defects and Spina Bifida Neural tube defects are a certain type of birth defect of the brain, spine, and/or spinal cord. Neural tube defects can result in nerve damage, learning disabilities, paralysis, and death. The... read more .
Mercury in seafood
Consuming too much mercury in seafood may harm the fetus. However, seafood contains nutrients that are important for growth and development of the fetus and breastfed infants. Thus, the Food and Drug Administration (FDA) recommends the following for women who are pregnant, who may become pregnant, or who are breastfeeding:
Do not eat tilefish from the Gulf of Mexico, shark, swordfish, big-eye tuna, marlin, orange roughy, and king mackerel.
Limit the amount of albacore tuna eaten to 4 ounces (one average meal) a week.
Before eating fish caught in local lakes, rivers, and coastal areas, check local advisories about the safety of such fish, and if mercury levels in the fish are not known to be low or if no advice is available, limit the amount eaten to 4 ounces (one average meal) a week and do not eat other high-mercury seafood during that week.
Each week, eat 8 to 12 ounces (2 or 3 average meals) of a variety of seafood that is lower in mercury.
Tilefish from the Gulf of Mexico have the highest levels of mercury of all fish (as tested by the U.S. Food and Drug Administration (FDA), but tilefish from the Atlantic Ocean can be safely eaten.
Seafood that is lower in mercury includes flounder, shrimp, canned light tuna, salmon, pollock, tilapia, cod, and catfish (see Advice about Eating Fish For Those Who Might Become or Are Pregnant or Breastfeeding and Children Ages 1–11 Years). Some authorities (Consumer Reports: Choose the Right Fish To Lower Mercury Risk Exposure) advise against eating any tuna during pregnancy.
More Information
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
Centers for Disease Control and Prevention (CDC): Sexually Transmitted Diseases During Pregnancy: This web site provides links to a fact sheet about pregnancy and sexually transmitted infections (STIs), statistics (including links to the prevalence of different STIs and their effect on pregnant women and their infants), and links to treatment of different STIs. It also provides links to general information about pregnancy and STIs.
U.S. Food and Drug Administration (FDA): Advice about Eating Fish For Those Who Might Become or Are Pregnant or Breastfeeding and Children Ages 1–11 Years: This web site provides information that can help pregnant women (as well as other women and parents of young children) choose fish that are nutritious and safe to eat.
Consumer Reports: Choose the Right Fish To Lower Mercury Risk Exposure: This web site identifies which fish are low in mercury and which are not. It also discusses how much mercury is too much.
Drugs Mentioned In This Article
| Generic Name | Select Brand Names |
|---|---|
lithium |
Eskalith, Eskalith CR, Lithobid |
azithromycin |
Azasite, Zithromax, Zithromax Powder, Zithromax Single-Dose , Zithromax Tri-Pak, Zithromax Z-Pak, Zmax, Zmax Pediatric |
erythromycin |
A/T/S, Akne-mycin, E.E.S., Emcin Clear , EMGEL, E-Mycin, ERYC, Erycette, Eryderm , Erygel, Erymax, EryPed, Ery-Tab, Erythra Derm , Erythrocin, Erythrocin Lactobionate, Erythrocin Stearate, Ilosone, Ilotycin, My-E, PCE, PCE Dispertab , Romycin, Staticin, T-Stat |
cocaine |
GOPRELTO, NUMBRINO |
