Congratulations on your pregnancy!
4 weeks is very early to learn of your pregnancy, and at 4 weeks gestation, your baby is just a tiny ball of cells known as a blastocyst – and is smaller than a poppy seed.
How is gestation calculated?
Calculation of gestation can be confusing. In obstetric terms, 4 weeks gestation means 4 weeks from your last menstrual period and 2 weeks from conception – when the egg meets the sperm in the Fallopian tube. This is assuming you have a regular 28 day menstrual cycle.
So, it follows that from 0 weeks of gestation to 2 weeks gestation you were not yet pregnant. This calculation for gestation convention began a long time ago, before pregnancy tests, before ultrasound examinations and before we even understood about fertilisation and embryology!
So, at 0 weeks gestation up until 3 ½ weeks gestation the pregnancy test will be negative, and by 4 weeks gestation it might just be faintly positive.
Is it necessary to have an ultrasound at 4 weeks gestation?
At 4 weeks, the blastocyst is splitting into an embryo and placenta, and an ultrasound of your uterus will only show what looks like a tiny dot called the gestational sac, and will not show a pregnancy until it is further advanced. Your pregnancy needs to be at least 5 weeks for it to be seen with even the most advanced transvaginal ultrasound equipment and the most experienced sonographer operating the equipment.
Sometimes in early gestation, the Ultrasound Care team can get hints of a pregnancy on ultrasound as we can see which ovary has ovulated by looking for the corpus luteum. This is a cyst which forms on the ovary releasing hormones to keep the uterus lining stable until the pregnancy is big enough to produce its own hormones. The lining of the uterus will be thick and bright, reflecting changes made to the lining by the hormones released by the ovary and your natural cycle.
Pregnancy check list at 4 weeks gestation
Even though it is early, you can still get started on preparing for your baby. Start with:
- Scheduling an appointment with your doctor for your first prenatal visit. This might not be available for the next couple of weeks so arrange to book in. Your doctor will then be able to arrange for a urine or blood test to confirm your pregnancy.
- If you’re not already taking a pregnancy vitamin or folic acid supplement – get started!
- Adopt healthy diet and lifestyle habits. Stop smoking and drinking alcohol, opt for healthy food choices and drink lots of water.
Next steps for your first pregnancy ultrasound
Speak to your doctor about arranging for your first ultrasound visit to check on your pregnancy. Ultrasound Care recommends the first ultrasound scan be undertaken at 6-7 weeks gestation for high risk pregnancies and otherwise at 8-10 weeks gestation.
If you would like to find out more about your first ultrasound scan or dating scan and what is involved and can be seen, please click here to visit our Dating Scan page or call us at a location of your choice to arrange for an appointment.