What Causes Implantation Cramping?

By BSc, MSc (embryologist) and BA, MA (fertility counselor).
Last Update: 08/19/2015

Implantation occurs when the egg –once fertilised by the sperm– attaches itself to the uterine wall. There, the development of the placenta will take place, which purpose is to provide blood and nourishment to the developing fetus.

The different sections of this article have been assembled into the following table of contents.

When does implantation occur?

Once the egg has been fertilised by the sperm, the developed zygote begins a journey down the Fallopian tubes to the uterus, where it will remain attached to the uterine wall. In case fertilisation does not occur, the egg will travel to the uterus, but it will be expelled during the menstrual period. Implantation occurs approximately seven days after ovulation.

Cramps when pregnant

Cramps are an early and completely normal symptoms. They are a sign that the body is preparing for the nine months of pregnancy and should not include fever or excessive bleeding. If the woman has a history of miscarriages or if the cramps persist for longer than usual, a doctor should be consulted.

Cramping may occur at any stage of pregnancy. At each stage, however, its meaning may vary.

Cramping during implantation

These cramps happen during the first weeks of pregancy and are often  accompanied by bleeding, usually referred to as implantation bleeding. Some women usually describe implantation bleeding as an unimportant period; nonetheless, others see it as the colour of “old blood”. These kind of cramps indicate that the fetus has attached itself to the uterine walls and, therefore, the woman is pregnant. Approximately, only one in every four women bleeds during implantation.

It consists of a lower abdominal pain. Indeed, it begins as soon as the egg is fertilised by the sperm rather than when implantation within the uterine wall occurs. These cramps should not be felt for more than one or two days at most. If the cramps presist, the woman should consult a doctor in order to dismiss the possibility of a miscarriage, an ectopic pregnancy, placental abruption, pre-eclampsia, urinary tract infection, preterm birth

Cramping in early pregnancy

Many women tend to think that these cramps indicate that miscarriage is on its way. However, they are, most of the time, the continuation of implantation cramping. They occur because, when the zygote attaches itself to the uterine wall the uterus starts to grow in order to carry the baby for 9 months.

Round Ligament Pain (RLP)

This type of pain is connected with cramps felt in later pregnancy stages. It usually consists of a light and continuous pain, especially after changing position.

It occurs because the muscle located under the uterus expands itself and grows in order to support the weight of the baby as it grows up.

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Authors and contributors

 Clara Miret Lucio
Clara Miret Lucio
BSc, MSc
Embryologist
Bachelor's Degree in Pharmacy from the University of Valencia (UV). Master's Degree in Biotechnology of Human Assisted Reproduction from the UV. Experience as a pharmacist and embryologist specialized in Reproductive Medicine at Valencian Infertility Institute (IVI), and currently at Equipo Juana Crespo (Valencia, Spain). More information about Clara Miret Lucio
Adapted into english by:
 Sandra Fernández
Sandra Fernández
BA, MA
Fertility Counselor
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández

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