What is A Placental Lake And How Does It Affect Pregnancy?

✔ Research-backed

An ultrasound may show placental lakes during pregnancy; these are enlarged blood-filled spaces in the placenta. Placental lakes can be visible on the ultrasound image as one or several black areas. The placenta nourishes the unborn baby, and it is essential to have a healthy placenta for optimal fetal growth and development.

Having one or two smaller placental lakes is not a cause of concern for maternal health. However, many women may have them in the third trimester. The obstetric/gynecology specialists recommend the following step based on your gestational age, fetus size, and the size of the placental lakes present. Read on to know more about placental lakes in pregnancy, when it is a concern and how it affects the pregnancy.

In This Article

What Are Placental Lakes?

Placental lakes or placental venous lakes are spaces within the placenta filled with maternal blood. A placental lake could contain small dilated veins with maternal blood flowing through them (1) (2).

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Areas in the placenta that appear dark on ultrasound examination are referred to as placental lakes, placental venous lakes, placental lacunae or placental caverns (8).

How Common Are Placental Lakes?

Placental lakes are less common. A few studies indicate that placental lakes can have an occurrence rate of 2.2% to 17.8% (3).

What Causes Placental Lakes?

The causes of placental lakes are not entirely known. It is usually believed that they are avillous vascular spaces, that is, spaces within the placenta with no placental tissue but only blood vessels flowing through (3). Placental lakes may occur when the placenta is a bit thicker than usual (4).

Dr. Michael Green, MD, the site director for OBHG at Northridge Medical Center in Northridge, CA, informs, “According to a 2012 medical study, larger placental lakes were linked to small-for-gestational-age status.”

Are Placental Lakes Harmful During Pregnancy?

Placental lakes generally do not cause fetal anomalies.

Image: Shutterstock

The occurrence of a placental lake is a normal feature, and seldom a point of concern for any fetal distress. Experts state that placental lakes have little to no clinical significance (5).

Dr. Green confirms, “Placental lakes are usually not a cause for concern during pregnancy. In fact, some of them reduce in size before ultimately disappearing altogether.”

Research has found no difference in the pregnancies of women with placental lakes and those without placental lakes. There was no adverse event during the pregnancy due to placental lakes. No anomalies in the baby’s gestational age and birth weight were observed (6).

When Can Placental Lakes Be Dangerous?

Placental lakes can be of concern in the first trimester.

Image: Shutterstock

Placental lakes can be of concern in the following situations (4) (7).

  • They occur early, in the first trimester or early second trimester
  • Presence of more than three placental lakes
  • The diameter is more than two centimeters
  • Large placental lakes with a diameter greater than five centimeters

protip_icon Research finds
As per a study, large placental lakes were found to have correlation with small for gestational age fetal status (9).

In such cases, Dr. Green advises, “If placental lakes persist or become larger, it’s important to keep up with doctor’s visits to ensure everything is going smoothly. However, most pregnancies remain healthy despite the presence of placental lakes.”

Complications Of Placental Lakes

Placental lakes can be a complication only if they are affecting the growth of the fetus.

The problems caused by them may or may not happen, and you may even give birth to a healthy baby. Therefore, do not panic if you have placental lakes. Any complication related to the pregnancy is quite likely to be detected and treated early if you visit the doctor for a regular ultrasound examination.

Can Placental Lakes Be Treated?

There is no specific treatment for placental lakes. If your doctor finds a placental lake during a routine ultrasound, then your pregnancy may be monitored more closely through a doppler ultrasound.

Do Placental Lakes Go Away?

A study monitoring placental lakes in pregnant women found that some lakes tend to decrease in size, some disappear, while some remain (7). Any changes to the size and presence of placental lakes will be detected during your routine ultrasound examination.

Frequently Asked Questions

1. Can placental lakes cause preterm labor?

No correlation or association has been reported between the presence of placental lakes and preterm labor.

2. Can placental lakes cause miscarriage?

No correlation or association has been reported between the presence of placental lakes and miscarriage.

3. What are the differences between placental lakes and other placental abnormalities?

The differences between placental lakes and other placental abnormalities lie in their associated complications. Placenta previa, which occurs when the placenta partially or wholly covers the cervix, and placenta accreta, increta, or percreta, which happen when the placenta attaches too deeply inside the uterine walls, can result in adverse pregnancy outcomes such as bleeding, the need for cesarean delivery before the due date, or surgical treatment of the uterus (10). However, placental lakes are seldom associated with such complications.

Placental lakes during pregnancy are seldom a cause for concern and do not trigger any complications for the mother or the baby. But suppose these pools of blood are seen during the early stages of pregnancy or are more than five centimeters in diameter; they might be harmful and require immediate medical intervention. Thus, do not get worried if your ultrasound has reported the presence of a small placental lake. They will dissolve on their own. Get enough rest and eat healthily for optimum prenatal care and health of the baby.

Infographic: What Conditions Are Associated With Placental Lakes?

Placental lake in early pregnancy can be an indication of underlying conditions. Large-sized placental lakes in the last trimester can be a cause for concern. Early management of the reasons may prevent adverse outcomes in some cases. Go through the infographics to learn more about the conditions associated with placental lakes in pregnancy.

conditions associated with placental lakes (infographic)

Illustration: Momjunction Design Team

Key Pointers

  • Placental lakes are black areas visible on ultrasound, representing enlarged blood-filled spaces in the placenta.
  • The incidence of placental lakes is reported to range from 2.2% to 17.8%, making them less common.
  • Placental lakes may be due to a villous vascular space and can occur when the placenta is thicker than usual, but their exact origin is unknown.
  • If there are more than three placental lakes in the first trimester, they may be a cause for concern.
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MomJunction's articles are written after analyzing the research works of expert authors and institutions. Our references consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.

1. Zaidi S.F. et al., Comprehensive imaging review of abnormalities of the placenta; Ultrasound quarterly
2. Fadl S. et al., Placental imaging: normal appearance with review of pathologic findings; Radiographics
3. B.D. Kulas et al., An Unusual Prenatal Ultrasound Image of Placental Lake in High Risk Pregnancy; Nepal Journal of Obstetrics and Gynaecology
4. Thompson M.O. et al., Are placental lakes of any clinical significance?; National Center for Biotechnology Information
5. Holzman J. et al., Ultrasound of the  Placenta; Donald School Journal of Ultrasound in Obstetrics and Gynaecology
6. N.S.V. Reis et al., Placental lakes on sonographic examination: correlation with obstetric outcome and pathologic findings; Journal of Clinical Ultrasound
7. H.S. Hwang et al., The clinical significance of large placental lakes; European Journal of Obstetrics & Gynecology and Reproductive Biology
8. Déborah Gavanier et al.; Vesicules or placental lakes in ultrasonography, determining the correct etiology; Journal of Gynecology, Obstetrics and Human Reproduction

9. Han Sung Hwang et al.; The clinical significance of large placental lakes; European Journal of Obstetrics & Gynecology and Reproductive Biology
10. Types of Placental Disorders; New England Center for Placental Disorders
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Dr. Sangeeta Agrawal
Dr. Sangeeta AgrawalFRCOG, MD, DNB, DGO
Dr. Sangeeta Agrawal is an obstetrician and gynecologist with around 29 years of experience in the field. She worked in Royal London, St. Bartholomew’s, North Middlesex, and Barnet General hospitals in London and currently runs her clinic in Mumbai.

Read full bio of Dr. Sangeeta Agrawal