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

check_icon Research-backed

Image : Shutterstock


An ultrasound may show placental lakes in 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 growth and development.

Having one or two smaller placental lakes is not a cause of concern. However, many women may have them in the third trimester. The OBG/GYN recommends 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.

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).

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).

Are Placental Lakes Harmful During Pregnancy?

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

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 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.

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.

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, eat healthily, and take care of yourself and the baby.


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
The following two tabs change content below.

Dr. Sangeeta Agrawal

Dr. Sangeeta Agrawal worked in Royal London, St. Bartholomew’s, North Middlesex and Barnet General hospitals in London. Currently, she runs her own clinic in Mumbai. She is also attached to Bhatia Hospital, Breach Candy Hospital, Wockhardt Hospital, and Global Hospital. Her areas of expertise include obstetrics and gynecology, involving teenage care, antenatal, intrapartum, post-natal care, painless labor, fertility control, menopause... more

Dr Bisny T. Joseph

Dr. Bisny T. Joseph is a Georgian Board-certified physician. She has completed her professional graduate degree as a medical doctor from Tbilisi State Medical University, Georgia. She has 3+ years of experience in various sectors of medical affairs as a physician, medical reviewer, medical writer, health coach, and Q&A expert. Her interest in digital medical education and patient education made... more