External fetal monitoring and internal fetal monitoring during labor

In many hospitals, a baby's heartbeat is monitored throughout labor with external fetal monitoring and internal fetal monitoring. Fetal monitoring enables doctors to detect problems early.
External fetal monitoring can be done before your membranes rupture. A belt with a recorder is strapped to your abdomen to pick up the baby's heartbeat. Internal fetal monitoring monitors the baby more precisely. An electrode is placed on the fetal scalp to measure the fetal heart rate.

Fetal Blood Sampling during Labor

Fetal blood sampling is another way to evaluate how well a baby is tolerating the stress of labor. Before the test can be performed, your membranes must be ruptured and your cervix must be dilated at least 2 em (about an inch). The physician passes an instrument into the vagina and through the dilated cervix to the top of the baby's head, where it makes a small nick in the baby's scalp. The baby's blood is collected in a small tube, and its pH ( acidity) is checked.
Knowing the baby's pH level helps doctors determine if the baby is having trouble and is under stress. The test helps the physician decide whether labor can continue or if a Cesarean delivery is needed.

Evaluating Fetal Lung Maturity
The respiratory system is the last fetal system to mature. Premature infants commonly experience respiratory difficulties because their lungs are not yet mature. Knowing how mature the baby's lungs are helps your doctor make a decision about early delivery, if that must be considered.
If there are reasons the baby needs to be delivered early, fetal lung maturity tests can determine whether the baby will be able to breathe without assistance. The two tests used most often to evaluate a baby's lungs before birth are the L-S ratio and the phosphatidyl glycerol (PC) tests. Fluid for the tests is obtained by amniocentesis.

A New Test to Determine Oxygen Levels
We can now monitor baby's oxygen inside the womb, before birth. A new technology uses light to measure the oxygen level in fetal blood, providing accurate answers as to whether baby's oxygen levels are in a safe range. This approach, called OxiFirst fetal oxygen monitoring, is used during labor. A probe is placed inside the womb on baby's skin to measure the baby's oxygen level. It is not widely available at this time.