​Pregnancy Week 3: Baby is a Zygote

Baby is only a single cell zygote at pregnancy week 3.

Although fertilisation may have taken place, your "baby" is technically only a single cell big and is called a zygote. It will continue to divide and grow and will be generally known as an embryo until the 10th week of pregnancy.

At pregnancy week 3, the embryo will remain in your fallopian tubes for 3-4 days, multiplying. At the same time, the embryo will move along your tubes in the direction of your uterus. This migration takes 3-7 days.

Boy or girl? Baby’s sex depends on winning sperm’s chromosome

The sex of your child will be determined by the combination of both yours and your partner's genetic blueprint. Specifically, it depends on whether the "winning" sperm carried an X or Y chromosome. Mother's chromosome always gives an X. Therefore you would require an XX to make a girl and XY for a boy.



Contributed by

Related Articles

Public Events

02 Jul 2025
Programmes KKH Antenatal Programme
1-Day Intensive Course KKH Patient: $306 Non-KKH Patient: $326; 4-Week Course KKH Patient: $240 Non-KKH Patient: $296 Learn More
03 Jul 2025
Talks Health Talk: Nutrition Demonstration @ SHP-Bedok
​Free, no registration required. Please walk in to clinic at specified date and time. Learn More
04 Jul 2025
Talks Health Talk: Weaning Diet @ SHP-Tampines North
​Free, no registration required. Please walk in to clinic at specified date and time. Learn More
05 Jul 2025
Workshop KKH Child and Infant CPR Workshop
On-site  •  $25 per pax for KK Parenting Club Member; $35 per pax for Non-member Learn More