Pregnancy week 3
Week 3 of pregnancy is a time of anticipation, if a woman is trying to get pregnant, or of utter ignorance. Signs and symptoms during week 3 of pregnancy are not readily apparent. Although the baby is growing at an exponentially rapid speed, most women have not yet missed a period and think nothing of the slight bleeding that occurs during implantation, when the egg embeds itself into the uterine lining. A cramp-like pain on one side of the abdomen is the biggest indicator of conception at week 3. Also, a more than usual discharge of clear vaginal fluid can be a sign. Usually at week 3 of pregnancy the egg is fertilized. If more than one egg is fertilized by two sperm, the result is fraternal twins. Identical twins result when one egg divides into two. In this case, both are of the same genetic makeup and will have the same physical characteristics.
At 3 weeks pregnant, the baby is only about .006 inches long, or around the size of the head of a pin. During this week, amniotic fluid accumulates around the tiny embryo within a space that will ultimately develop into the amniotic sac, which cushions the baby for the entire pregnancy term. Although the placenta will not begin developing until week 4, the baby cleverly ensures itself all the nutrients it needs. The embryo, although just a ball of cells, employs a circulatory system which uses tubes that are attached to the uterine wall.
Most women will find that they are ovulating during week 3. This causes bloating and can be an early indicator of pregnancy. As soon as the notion of having conceived crosses a woman’s mind, she should take pains to take care of herself, watch her diet, and make healthy choices until she is sure. Modified forms of usual exercise are a great way to stay in shape during a pregnancy and can help women stay healthy. Testing for pregnancy will have to wait another 10 days from this point, or until around 2 or 3 days from when a period is expected.
Current guidance (today's medical sources): In week three the egg is usually fertilised; if two eggs are fertilised the result is fraternal twins, while one egg dividing produces identical twins. The baby is only about 0.006 inch long — roughly the head of a pin — and amniotic fluid begins to gather around the embryo in the space that becomes the amniotic sac. The placenta does not develop until week four, but the embryo already draws nutrients through tubes attached to the uterine wall. Signs are seldom obvious; a cramp-like pain on one side of the abdomen or extra clear discharge can be early clues. A pregnancy test is usually not reliable for another ten days or so.
Contact your healthcare provider promptly about heavy vaginal bleeding, severe or persistent abdominal pain, a high fever, severe or sudden headache, vision changes, or fainting. Seek urgent care if you are worried — these can be signs that need medical attention.
Sources: NHS — Pregnancy weeks 1–3; MedlinePlus (NIH/NLM) — Prenatal Care; Mayo Clinic — Fetal development: The 1st trimester. Informational only. See our sources & medical-review policy.
Frequently asked questions
How many months is 3 weeks pregnant?
Week 3 falls in the first trimester. Pregnancy is usually counted in weeks (about 40 in total) rather than months, because weeks are more precise.
What is happening to the baby at 3 weeks?
The fertilised egg multiplies into a ball of cells called a blastocyst and begins to implant in the uterine lining.
What symptoms are common at week 3?
Symptoms are rarely apparent; a one-sided cramp-like pain, light implantation bleeding, or extra clear discharge may occur. Symptoms vary a lot from person to person; discuss anything that worries you with your healthcare provider.
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See the week-by-week guide →Informational only — not medical advice. Pregnancy Week to Week is a general educational reference. It is not a substitute for professional medical care, diagnosis, or treatment. Every pregnancy is different: always consult your doctor, midwife, or other qualified healthcare provider about your own pregnancy, and never disregard or delay professional advice because of something you read here. In an emergency, contact your maternity unit or local emergency number immediately.