Marie, during my 21-week ultrasound, my doctor told me I have a “venous lake.” He said it very quickly and didn’t really explain it, and I went back home. Now I have tons of questions! Is this serious for my baby? Where’s this lake? Is it likely that I will bleed more? Are there risks during childbirth?

I figure he would have told me if it was dangerous, but faced with this unknown situation, I am somewhat concerned. I would like to know what is happening to me. Thanks for any information you can give me, and for everything you do for us. Rosanna

Hello Rosanna,

That’s an excellent question, and you are right to ask for more information to get reassurance.

In fact, venous lakes are seen frequently during ultrasounds, especially during the last trimester, but few doctors will tell you because it will not change the way you handle your daily activities. There may be one or many lakes. 

Venous lakes are also called placental lakes, or blood clots in the placenta. These terms refer to an accumulation of blood in certain parts of the placenta, thus why they are called lakes. This doesn’t mean that you will bleed more, or that the placenta will separate, the baby will lack blood for their growth, have a higher risk for premature birth or hemorrhage after childbirth. A venous lake is not a risk for you or your baby. 

When the radiologist or ultrasound technician sees this phenomenon, they only make sure that the rest of your parameters are normal, and if so, the rest of your pregnancy will go as usual. If the venous lake seems more substantial than average, the doctor may request a control ultrasound to verify the baby’s growth. 

The causes of venous lakes are unknown, but it may be associated with a placenta that is rooted deeper in the uterus, which is called accrete (see my article called Let’s Talk Placenta). It may also be associated with women who have had uterine surgery.

Rosanna, I hope my answer has reassured you a bit.


The Baby Expert