Human Placental Lactogen — Explained by Medical Evidence, Not Myths

Human placental lactogen, often shortened to hPL, is a normal pregnancy hormone produced by the placenta. It helps direct nutrients toward the developing baby and contributes to the natural insulin resistance that occurs later in pregnancy.

What Is Human Placental Lactogen?

Human placental lactogen is a hormone made by the placenta, the temporary organ that supplies oxygen and nutrients to the developing baby during pregnancy. It is also called human chorionic somatomammotropin, or hCS. The hormone becomes detectable early in pregnancy and generally increases as the placenta enlarges.

hPL has effects that resemble, in part, those of growth hormone and prolactin. Its main role is not to signal that something is wrong or right with a pregnancy on its own. Instead, it is one component of the complex hormonal system that helps the pregnant person’s body adapt to supporting fetal development.

Online discussions can sometimes portray hPL as a simple measure of placental health, fetal health, or diabetes risk. Medical evidence is more nuanced. While hPL reflects placental activity, its value varies widely between individuals and is not usually used as a standalone test for monitoring a normal pregnancy.

What Does hPL Do During Pregnancy?

One important function of hPL is to help shift maternal metabolism so that a steady supply of nutrients is available to the fetus. In particular, it contributes to reduced sensitivity to insulin, especially in the second half of pregnancy. This means the mother’s body may keep more glucose circulating in the blood, making it available for placental transfer.

hPL also promotes the use of stored fat for energy. This metabolic adjustment can help preserve glucose and amino acids for the developing baby. These changes are normal adaptations of pregnancy, although they can reveal a tendency toward high blood sugar in people who are already susceptible to diabetes.

The hormone may also contribute to breast development in preparation for breastfeeding. However, milk production after birth depends on several hormones and on the delivery of the placenta. hPL should therefore not be viewed as a direct predictor of whether a person will be able to breastfeed.

How hPL Levels Change Through Pregnancy

hPL levels usually rise progressively throughout pregnancy. The concentration is related broadly to the amount of functioning placental tissue, so levels tend to be higher later in pregnancy than in the first trimester. A single result must always be interpreted in the context of gestational age, laboratory methods, symptoms, ultrasound findings, and the overall clinical picture.

Reference ranges may differ between laboratories, and normal values overlap considerably. For this reason, an hPL result cannot reliably estimate a baby’s size, predict a baby’s health, or confirm that placental function is normal by itself. A result outside an expected range does not automatically mean that there is a pregnancy complication.

In selected clinical or research settings, clinicians may consider placental hormones alongside other assessments. In day-to-day maternity care, ultrasound evaluation, blood pressure monitoring, fetal growth assessment, and established blood tests are generally more informative for specific concerns.

hPL, Insulin Resistance, and Gestational Diabetes

Pregnancy naturally becomes more insulin-resistant as it progresses. hPL is one of several placental hormones involved in this process. Insulin resistance helps ensure that glucose remains available to the fetus, but the pancreas must produce more insulin to keep the pregnant person’s blood glucose within a healthy range.

If the body cannot make enough additional insulin, blood glucose may rise and gestational diabetes can develop. hPL contributes to this normal physiological shift, but it is not the sole cause of gestational diabetes. Family history, previous gestational diabetes, polycystic ovary syndrome, body weight, age, ethnicity, and other factors can also influence risk.

Testing for gestational diabetes is performed with established glucose-based screening and diagnostic tests, commonly during the second trimester or earlier when risk is higher. Measuring hPL is not a replacement for these tests. People with concerns about glucose results should follow the plan recommended by their maternity care team.

Is Human Placental Lactogen Testing Needed?

Most pregnant people do not need an hPL blood test. It is not part of routine prenatal screening in many healthcare systems because it has limited ability to diagnose or rule out common pregnancy concerns when used alone. Modern prenatal care relies on tests that have clearer roles for particular clinical questions.

In the past, hPL testing was sometimes considered in the assessment of suspected placental insufficiency or fetal growth concerns. However, changes in hPL may occur for many reasons, and results do not provide enough certainty to guide care independently. Ultrasound-based growth monitoring, Doppler studies when appropriate, fetal surveillance, and maternal assessment are generally more useful tools.

If a clinician has ordered an hPL test, it is reasonable to ask why it was selected, what result range the laboratory uses, and how the result will be considered with other findings. Test interpretation should be individualized rather than based on information from online charts or non-medical sources.

Common Myths and Evidence-Based Facts

Myth: A high hPL result means a person has gestational diabetes. hPL can contribute to insulin resistance, but a high or low level does not diagnose gestational diabetes. Glucose testing is needed to assess blood sugar regulation accurately.

Myth: Low hPL always means the placenta is failing. A result may prompt a clinician to consider the wider clinical context, but it cannot confirm placental problems alone. Pregnancy dating, laboratory variation, placental size, multiple pregnancy, and many other factors can affect hormone levels.

Myth: hPL predicts breastfeeding success. hPL participates in breast development during pregnancy, but breastfeeding outcomes depend on many factors, including milk removal after birth, infant feeding ability, support, health conditions, and access to lactation guidance. A hormone measurement during pregnancy cannot predict the whole breastfeeding experience.

When to Seek Medical Care

Pregnant people should contact their maternity care team promptly if they notice vaginal bleeding, fluid leakage, severe or persistent abdominal pain, severe headache, visual changes, sudden swelling of the face or hands, shortness of breath, fever, or a clear reduction in fetal movements after movements have become regularly noticeable. These symptoms require clinical assessment and should not be attributed to hormones without medical advice.

A person should also discuss symptoms that may be associated with high blood glucose, such as unusual thirst or frequent urination, especially if they have been advised that they are at increased risk of gestational diabetes. These symptoms are not specific, and many people with gestational diabetes have no symptoms, which is why routine recommended screening remains important.

For questions about hormone testing, pregnancy symptoms, fetal growth, or diabetes screening, an obstetrician, midwife, or maternal-fetal medicine specialist can provide individualized guidance. Acibadem International’s multidisciplinary specialists and JCI-accredited hospitals also assess and treat pregnancy-related health concerns for international patients.

Frequently asked questions

Is human placental lactogen the same as hCG?

No. Human placental lactogen and human chorionic gonadotropin, or hCG, are different hormones made by the placenta. hCG is the hormone detected by most pregnancy tests, while hPL mainly helps regulate metabolism and supports pregnancy-related breast development.

What is another name for human placental lactogen?

Human placental lactogen may also be called human chorionic somatomammotropin, abbreviated hCS. Both terms refer to the same placental hormone. Healthcare professionals may use either name in laboratory information or medical literature.

Can hPL cause gestational diabetes?

hPL contributes to the normal insulin resistance of pregnancy, which can make gestational diabetes more likely in susceptible individuals. However, it is only one of several hormones and risk factors involved. Gestational diabetes is diagnosed using blood glucose testing, not an hPL level.

Is a human placental lactogen blood test routine?

No, hPL testing is not routinely included in standard prenatal blood tests in many settings. Its result is difficult to interpret alone and does not replace ultrasound, fetal monitoring, or glucose screening. A clinician may occasionally request it in a specific context.

Do low hPL levels mean there is a problem with the baby?

Not necessarily. hPL levels vary by gestational age and laboratory method, and a single value cannot determine fetal well-being. If there is a concern, clinicians usually review the result together with ultrasound findings, pregnancy dating, maternal health, and other assessments.

Does hPL affect breastfeeding after delivery?

hPL helps prepare breast tissue during pregnancy, but it is not the only hormone involved in lactation. After delivery, changes in progesterone and estrogen, along with regular milk removal, are especially important for milk production. An hPL result cannot predict breastfeeding success.

References

• American College of Obstetricians and Gynecologists
• National Institute of Diabetes and Digestive and Kidney Diseases
• Merck Manual Professional Edition
• World Health Organization

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.