Question

Describe the hormonal changes that occur as a result of implantation, including production of human chorionic gonadotropin (HCG) to maintain the corpus luteum and increased production of progesterone by the corpus luteum

Answer 1

When the fertilized egg implants itself in the uterus, around one-third of women will notice light bleeding or spotting, which is called implantation bleeding.

This spotting typically lasts only a day or two and is very light in flow. Implantation bleeding is one of the earliest signs of pregnancy since it happens around the time the woman becomes pregnant.

However, even when a woman notices bleeding around the time of implantation, they may still not get a positive pregnancy test. They may have a very early miscarriage called a chemical pregnancy, or the bleeding might be due to something else.

At implantation, the body begins producing a pregnancy hormone called human chorionic gonadotropin (hCG). Known as the pregnancy hormone, hCG — along with progesterone and estrogen — is responsible for early pregnancy symptoms. It is also the hormone that pregnancy tests identify.

However, it can take several days for hCG to reach to a detectable level, so pregnancy tests may not pick up the hormone, and symptoms may not develop immediately.

A few days after implantation, hCG levels may be high enough to cause early pregnancy symptoms. However, this is also the phase of the menstrual cycle when a woman is most likely to experience symptoms that mean they are about to get their period.

Women who are aware of how their body behaves each month might be better able to identify whether their symptoms are due to pregnancy or regular menstruation.

Some other symptoms of early pregnancy include:

• darkening in the color of the nipples
• fatigue
• food cravings or increased hunger
• increased need to use the bathroom
• gastrointestinal changes, such as cramping or diarrhea

Some of the most common include:

• dizziness or lightheadedness due to hormonal shifts and changes in the blood pressure and heart rate
• nausea, especially when hungry
• vomiting
• strong aversions to certain foods or smells
• changes in the sense of smell
• fatigue
• bloating and water retention.

Women will not experience any pregnancy symptoms during the earliest part of the luteal phase. This is because pregnancy does not occur until the fertilized egg implants into the wall of the uterus.

During the luteal phase, the body produces more progesterone, which is a hormone that helps sustain an early pregnancy. The levels of progesterone peak at 6–8 days after ovulation, even when a woman does not become pregnant.

Progesterone levels can affect a woman’s mood and body — this means that after a week or so, they may experience similar symptoms in early pregnancy as they do before a period.

When a fertilized egg reaches the uterus, it implants itself into the wall of the uterus. This is called implantation and marks the start of pregnancy. Implantation typically happens 6–12 days after fertilization.