You are 17 weeks and 2 days

The tiny embryo was once dwarfed by the placenta, but now your baby has outgrown it and will keep doing so.

159 days until your due date

In early pregnancy, the placenta grew much faster than your baby. Now your baby has caught up and from here on will be bigger than the placenta.

The placenta's structure will change over the next few weeks as its second wave of cells moves into the spiral arteries of the uterus. It's at its thickest now, but as it keeps growing, more slowly for a while, it will thin out.

Because your baby is growing faster, at 2.5 oz (70 g) she's now heavier than the placenta, and by full term she'll weigh six or seven times as much. Nutrients from the placenta give her energy to grow, but her growth is partly controlled by her own insulin and insulin-like growth factors. She has fairly high levels of growth hormone, which drives growth after birth, but it doesn't seem to play an important role before birth.

Explainer

A typical position

The baby lies in a typical curled position with feet and elbows bent. The well-developed ear is still a little low on the side of the head, and the blood vessels show up well.

Focus on

Health: Tackling heartburn

If you're struggling with the burning feeling and sour taste of heartburn, try these:

Eat smaller meals and chew your food well.
Avoid foods that make it worse, such as spicy, rich, and fatty dishes.
Don't smoke or drink alcohol.
Drink milk.
Wear loose clothing.
Chew gum after eating, but not mint flavors.
Stay upright after meals, because bending can make it worse.
Don't eat in the 2–3 hours before bed.
Raise the head of your bed by 6 in and lie on your left side.

This is general information based on NHS guidance, not medical advice, and every pregnancy is different. Talk to your midwife or GP about anything that worries you. If your baby's movements slow down or change, or you have bleeding, severe pain or leaking fluid, call your maternity unit straight away. In an emergency, call 999.