1 week pregnant: Changes for mum and baby

Changes for mum

In the week after your menstrual bleeding begins, you are in what is known as the follicular phase of your menstrual cycle, which lasts for 10-14 days. The follicular phase lasts until week 2 when ovulation occurs, that is, when your ovaries release a mature egg.

During the follicular phase, your ovaries begin preparing an egg for fertilisation, stimulated by a hormone your body produces called follicle stimulating hormone (FSH). The ovaries contain thousands of follicles and each follicle contains a single, immature egg (oocyte). FSH stimulates the follicles to enable the eggs to mature.

Typically one follicle becomes dominant in the first week (by day 5-7) following the beginning of your last menstrual bleeding. The dominant follicle is the one which receives the greatest supply of blood and produces the greatest amount of oestrogen and granulosa aromatase, an enzyme which helps convert androgens (such as the hormone testosterone) to oestrodial (a form of oestrogen).

The single egg that the dominant follicle contains is typically the only egg to fully mature and be released into the fallopian tubes for fertilisation (day 10-14). However, sometimes more than one follicle becomes dominant, and it is at these times that a woman may conceive a multiple pregnancy, that is, twins, triplets or a greater number of babies. The oestrogen produced by the dominant follicle triggers the production of another hormone, luteinising hormone (LH), 5-7 days after the start of your menstrual bleeding. This is the hormone responsible for the final maturation of the single egg in the dominant follicle, in preparation for ovulation.

At the same time, the changing hormone levels stimulate changes in the lining of your womb, known as the endometrium. It becomes 2-3 times thicker and holds 2-3 times more water about 9 days after your menstrual bleeding.

Changes for baby

Your baby has not started growing yet as the single egg which will mature in this menstrual cycle remains in your ovaries, where it is maturing. Only once the egg is released from the ovaries by ovulation in week two, typically 10-14 days after your menstrual bleeding began, can it be fertilised and begin the process of growing into a beautiful little boy or girl.

References

More information on the 1^st week of pregnancy

For more information on the first week of pregnancy, see 1 week pregnant.

For more information about preparing your body for pregnancy with healthy eating and exercise, see Women’s health and lifestyle tips for getting pregnant this week.

For more information about optimising your health before pregnancy, see Doctor appointments and tests this week.

For more information about how to improve the chances of getting your partner pregnant, see Men’s health and lifestyle tips to boost fertility and sperm health this week.

For more information about the key points of the first week of pregnancy, see Key points this week.