Risk Factors for High-Risk Pregnancy - 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 (a type of high blood pressure that develops during pregnancy)
- Preterm labor
- Anemia
Adolescents can have babies who are born underweight (small-for-gestational age). 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. 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 or diabetes
- Problems related to the pregnancy, such as preeclampsia, gestational diabetes (diabetes that develops during pregnancy), chromosomal abnormalities in the fetus, and stillbirth
- Complications during labor, such as difficult labor or a placenta that detaches too soon (placental abruption) or is mislocated (placenta previa)
Children of women aged 35 or older are more likely to have birth defects, such as heart defects. a narrowed esophagus (esophageal atresia), a defect of the urethra called hypospadias, or a defect of the skull called craniosynostosis.
As women age, genetic evaluation for chromosomal abnormalities becomes more important. In older pregnant women, ultrasonography may be done to help determine whether the fetus has birth defects,
Weight
Very thin women—with a body mass index (BMI) of less than 19.8 (see table Determining Body Mass Index)—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), which may be difficult to deliver
- Babies who are born underweight (small-for-gestational age)
- Babies with birth defects
- Miscarriages and stillbirth
- Gestational diabetes
- Gestational hypertension (high blood pressure that first develops after 20 weeks of pregnancy)
- Preeclampsia (gestational hypertension accompanied by protein in the urine)
- A pregnancy that lasts 42 weeks or longer (postterm pregnancy)
- Need for a cesarean delivery
Height
Women shorter than 5 feet are more likely to have a small pelvis, which may move 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. Also, short women are more likely to have preterm labor and a baby who is born underweight (small-for-gestational age).
Reproductive abnormalities
Structural abnormalities in the uterus or cervix increase the risk of the following:
- A difficult labor
- A miscarriage during the 2nd trimester and preterm labor
- A fetus in an abnormal position
- Preterm labor or a premature baby
- Need for a cesarean delivery
Structural abnormalities include a double uterus, fibroids in the uterus, and a weak (incompetent) cervix (cervical insufficiency) that tends to open (dilate) as the fetus grows. Fibroids occasionally cause the placenta to be mislocated (called placenta previa), labor to begin too early (preterm labor), 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: