Your baby is about 14.2cm from head to bottom (crown to rump), almost the size of a capsicum, and weighs up to 190g (Hill 2019).
She looks more like a tiny human each day. Her head is smaller relative to her body size, and her legs have lengthened (Moore et al 2019a). The outer shells of her ears are clearly visible and are in their final position (Moore et al 2019a, Visembryo nd).
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Your baby is maturing inside her body, too. In her lungs, the main branching tubes are starting to develop tinier tubes at their tips. By the end of your second trimester, these tiny tubes will have sprouted air sacs (alveoli) (Moore et al 2019b). By the time your baby is born at full term, alveoli are laced with fine vessels through which blood flows to pick up oxygen, ready to circulate to her organs and tissues (Moore et al 2019b).
Your mid-pregnancy ultrasound scan (anomaly scan) is offered between 18 and 21 weeks (DH 2018, NHS 2017). So you'll soon get a glimpse of your baby kicking, flexing, reaching or even rolling (de Vries and Fong 2006).
During the anomaly scan, a sonographer will assess your baby's growth and development in detail. If you want to find out, and if your baby is in the right position, your sonographer may also be able to tell you your baby's sex (NHS 2017).
If you're having a girl, your baby's uterus (womb) is in place, and her vagina and fallopian tubes are developing (Moore et al 2019c). If you're having a boy, his penis will be distinct – it's growing rapidly now (Moore et al 2019c).
Check out our pregnancy guide to see what changes could be happening to you at 18 weeks pregnant.
Note: Every baby develops differently. This page is designed to give you a general idea of how a fetus grows in the uterus.
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de Vries JIP, Fong BF. 2006. Normal fetal motility: an overview. Ultrasound Obstet Gynecol 27(6):701-11
DH. 2018. Pregnancy care: clinical practice guidelines. Updated June 2019. Department of Health. Canberra: Department of Health. www.health.gov.auOpens a new window [Accessed March 2020]