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NIH MedlinePlus the Magazine, Trusted Health Information from the National Institutes of Health

Understanding Pregnancy and Birth Issues

What is a High-Risk Pregnancy?

All pregnancies involve a certain degree of risk to both mother and baby. But factors present before pregnancy or that develop during pregnancy can place the mother and baby at higher risk for problems. Women with high-risk pregnancies may need care from specialists or a team of health care providers to help promote healthy pregnancy and birth.

Factors present before pregnancy that can increase risk may include:

  • Being very young or old
  • Being overweight or underweight
  • Having had problems in previous pregnancies, such as miscarriage, stillbirth, or preterm labor or birth
  • Pre-existing health conditions, such as high blood pressure or diabetes
  • During pregnancy, problems may also develop even in a woman who was previously healthy. These may include such conditions as gestational diabetes or preeclampsia/eclampsia (dangerously high blood pressure). (Read more about gestational diabetes on page 10.)

Pregnancy Research at NICHD

NICHD conducts and supports research on topics related to the health of children, adults, families, and various populations. Among them are the following:


NICHD has been conducting and supporting research on preeclampsia, trying to zero in on the condition's cause. Finding the cause could help lead to a cure or to preventing preeclampsia from occurring in the first place.

A team of researchers from NIH and Beth Israel Deaconess Medical Center conducted recent studies on preeclampsia. The researchers found high levels of two proteins in the blood of pregnant women that appear to point to the later development of preeclampsia. The proteins also suggest the development of high blood pressure during pregnancy.

Preterm Birth

Among the main goals of NICHD research is finding a way to prevent births from occurring before an infant is strong enough to survive outside the womb. Women who have one preterm birth are considered to be at high risk for another preterm birth. Investigators have focused their attention on trying to prevent preterm birth among these high-risk women.

Researchers have had success using a treatment of a specific type of progesterone—called 17P. Progesterone is a hormone that the body makes to support pregnancy. An NICHD Maternal-Fetal Medicine Units (MFMU) Network study found that for women carrying one baby and with a history of preterm delivery, injections of 17P reduced preterm birth by one-third.

What Is Preeclampsia?

Preeclampsia is the development of high blood pressure, and protein in the urine of pregnant women. Preeclampsia is estimated to complicate from three to five percent of all pregnancies. Untreated, severe preeclampsia can lead to eclampsia. Eclampsia is dangerously high blood pressure and convulsions, which may result in disability or death for the mother. The only treatment for severe preeclampsia is immediate delivery of the baby.

In the United States, where treatments are available, few women die from preeclampsia itself. But, complications (such as kidney failure, hemorrhage, and stroke) from preeclampsia can lead to ongoing health problems. (Read about NICHD preeclampsia research in the sidebar.)

Preterm Birth

Preterm (premature) birth is birth before the baby is 37 weeks old. In 2003, one out of every eight infants born was preterm. (You may have heard them referred to as "preemies.")

Preterm infants are at high risk for a variety of disorders, including mental retardation, cerebral palsy, and vision impairment. These infants are also at high risk for long-term health issues, including heart attack, stroke, high blood pressure, and diabetes.


A C-section, also called a Cesarean delivery, is the birth of a baby through a surgical incision in the abdomen. The surgery is performed electively, or when a vaginal birth is not possible or is not safe for the mother or child.

Due to a variety of medical and social factors, C-sections have become fairly common. About 30 percent of all births in the United States in 2005 were C-sections.

Recently, there has been a lot of interest in C-sections to prevent complications that may arise with childbirth, notes NICHD's Dr. Spong. She explains that while the data clearly support an uncomplicated vaginal delivery as the safest way to give birth, it is important for women to know the risks and benefits of having a C-section. "The difficulty is that you don't know who is going to have an uncomplicated delivery," she adds.

Some of the main reasons for C-section instead of vaginal delivery include such conditions as abnormal development, abnormal positioning in the uterus, multiple babies, extreme maternal illness, and other situations that may threaten the welfare of the mother or baby.

Nowadays, C-sections are very safe procedures. Dr. Spong stresses that for women electing to have a C-section it is especially important to understand the risks and impacts a C-section may have on future pregnancies and the long-term health of the mother and child. This discussion is less critical for women who need a Cesarean delivery for maternal or fetal reasons. "Doctors should have a critical discussion with their patients about why they are interested in a C-section, what their concerns are, and what they are hoping to prevent."

Winter 2008 Issue: Volume 3 Number 1 Pages 22 - 23