Human placental lactogen is a hormone that’s released by the placenta during pregnancy. The placenta is a structure in the uterus that provides nutrients and oxygen to a fetus.

As the fetus grows, human placental lactogen levels gradually rise. After the pregnancy, human placental lactogen levels drop.

If you’re expecting, you’ll probably hear about your human placental lactogen levels occasionally. Here’s what you need to know about this hormone, including its function and how your levels are tested.

The placenta starts to produce human placental lactogen around the second week of pregnancy. By the third to the sixth week, human placental lactogen circulates throughout your body. Around week six, it’s detectable by a blood test.

Human placental lactogen levels continue to slowly rise throughout your pregnancy. If you’re carrying twins or other multiples, you’ll probably have higher human placental lactogen levels than those carrying a single fetus.

During a pregnancy, human placental lactogen plays these key roles:

  • Metabolism regulation. Human placental lactogen helps to regulate your metabolism, which is the use of fats and carbohydrates for energy. This helps to break down fats from foods more efficiently, allowing them to be used as energy. It also helps to free up glucose (sugar) for the fetus.
  • Insulin resistance. Human placental lactogen also makes your body less sensitive to the effects of insulin, a hormone that moves glucose from the bloodstream into the cells. This also leaves more glucose available in your bloodstream to nourish the fetus.

Although human placental lactogen has some effect on lactation, its exact role in stimulating milk glands in the breasts is unclear and doesn’t seem to be a major factor.

A human placental lactogen test is done just like any other blood test. Your doctor uses a needle to draw a small sample of blood from a vein in your arm. In most cases, you don’t need to do anything to prepare for the test.

Your doctor might order this test for a variety of reasons, especially if:

  • you had an unusual ultrasound
  • the amount of amniotic fluid surrounding the fetus drops
  • your doctor thinks there may be a problem with the placenta
  • you have high blood pressure
  • you may be having a miscarriage
  • you’re at risk of developing gestational diabetes

If your doctor is ordering a human placental lactogen test and you’re not sure why, don’t hesitate to ask them about it.

Your human placental lactogen levels can tell you a range of things about your pregnancy. But it’s important to walk through your results with your doctor. They’ll take into account your overall health, any underlying health conditions, and other blood test results to better understand what your human placental lactogen test results indicate.

Results showing a high level of human placental lactogen may be a sign of:

Results showing a low level of human placental lactogen may be a sign of:

Again, it’s important to remember that your human placental lactogen levels don’t indicate much on their own. Instead, doctors use it to check for signs of any potential issues that might require further testing or treatment.

A human placental lactogen test is just one of the tests your doctor may order during your pregnancy. It’s a good way to monitor the placenta and ensure the fetus is developing on schedule. It can also help to identify potential complications early on in your pregnancy.