Having chronic hypertension that starts before pregnancy or during the first 20 weeks of pregnancy can cause complications. Chronic hypertension can have harmful effects on a fetus, and it also increases the risk of developing other diseases in pregnancy. Between 1 and 5 percent of pregnant women have chronic hypertension, the U.S. Department of Health and Human Services reports. Women with this condition can have healthy babies, especially if they're aware of the possible risks and complications.
Intrauterine Growth Retardation
High blood pressure in a pregnant woman causes decreased blood flow through the placenta to the growing fetus. Since the fetus is dependent on the nutrients in maternal blood to grow, women with chronic hypertension may have babies with intrauterine growth retardation, or IUGR. Despite the somewhat frightening name, babies with this condition are not mentally retarded. They are smaller than normal for their gestational age and lack normal fat deposits under the skin. IUGR babies can have problems maintaining their temperature, low blood sugar, low oxygen levels and low Apgar scores, used to assess a baby's well being at birth, according to the Children's Hospital of Pittsburgh.
Medication Risks
A class of anti-hypertensive medications called ACE inhibitors may increase the risk of birth defects in infants whose mothers have chronic hypertension if given in the second or third trimesters of pregnancy. Kidney problems, underdeveloped lungs, skull deformity and fetal death can occur. Other medications such as lebetolol and atenolol may cause IUGR. The U.S. Department of Health and Human Services discovered this while reviewing research on anti-hypertensive medications. Older classes of blood pressure medications are safe for use in pregnancy.
Superimposed Pre-eclampsia
Women with chronic hypertension may also develop pre-eclampsia, a pregnancy condition characterized by elevated blood pressure, protein in the urine and swelling of the hands and face. Pre-eclampsia can lead to maternal kidney, liver and blood clotting problems, seizures and death. Fetal premature delivery or death may also occur. Since chronic hypertension doesn't cause proteinuria, a 24-hour urine collection can help diagnose superimposed pre-eclampsia in chronic hypertensives, according to the consumer information website GYN[OB].com.
Placental Abruption
Chronic hypertension can cause addition risk of developing placental abruption, a condition in which the placenta loosens prematurely from the uterine wall, the University of Virginia Health System states. Placental abruption can lead to maternal hemorrhage and fetal death if a large portion of the placenta detaches.
Preterm Delivery
Pre-eclampsia, placental abruption and IUGR can all lead to preterm delivery in cases of maternal hypertension. Babies born prematurely are at increased risk for a number of complications including breathing problems, infection and premature death.
References
- Agency for Health Research and Quality: Management of Chronic Hypertension in Pregnancy
- University of Virginia Health System: Chronic Hypertension
- GYN[OB].com: Hypertension in Pregnancy
- Children's Hospital of Pittsburgh: Intrauterine Growth Retardation
- University of Washington: Dr. Rose's Peripheral Brain; Eric Rose, M.D.
