28 weeks pregnant: fetal development

Medically reviewed by Joseph Aquilina, Consultant obstetrician and gynaecologist

Good news – you're now in your third trimester! Your baby weighs just over 1kg, about the same as an eggplant, and is at least 37.6cm long (Hill 2019).

Your baby's eyes are now ringed with delicate lashes (Moore et al 2019a, Visembryo nda). Soon, the muscle fibres (Lowth nd) that form your baby's irises will develop colour and pattern (Hill 2017, Visembryo ndb). But the final colour of her eyes won't be revealed until at least a few weeks after she's born (Daugman nd, Visembryo ndc).

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A white, fatty substance called myelin is slowly wrapping around your baby's spinal cord and the nerves that branch out from it (Moore et al 2019b). This process is called myelination, and it will continue during pregnancy and throughout your baby's first year (Daugman nd, Moore et al 2019b).

Myelin is important, as it helps to speed up messages between your baby's brain and the nerves around her body (Dangond 2019, Nave and Werner 2014). It also acts as a protective layer (Dangond 2019). The nerves that support your baby's movement are sheathed in myelin first, before the nerves that serve her senses (Moore et al 2019b).

Discover how pregnancy can affect your body and your life at 28 weeks pregnant.

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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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Sources

BabyCenter's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organisations, professional groups of doctors and other experts, and published studies in peer-reviewed journals. We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies.

Dangond F. 2019. Myelin sheath damage and multiple sclerosis (MS). emedicine health. www.emedicinehealth.comOpens a new window [Accessed March 2020]

Daugman J. nd. Anatomy, physiology, and development of the iris. University of Cambridge. www.cl.cam.ac.ukOpens a new window [Accessed March 2020]

Hill MA. 2017. The development of the human iris. University of New South Wales, Embryology. embryology.med.unsw.edu.auOpens a new window [Accessed March 2020]

Hill MA. 2019. Fetal development. University of New South Wales, Embryology. embryology.med.unsw.edu.auOpens a new window [Accessed March 2020]

Lowth M. nd. Anatomy of the eye. Patient, Health Info. patient.infoOpens a new window [Accessed March 2020]

Moore KL, Persaud TVN, Torchia MG. 2019a. Fetal period: ninth week to birth. Chapter 6 in The developing human: clinically oriented embryology. 11th ed. Elsevier

Moore KL, Persaud TVN, Torchia MG. 2019b. Nervous system. Chapter 17 in The developing human: clinically oriented embryology. 11th ed. Elsevier

Nave KA, Werner HB. 2014. Myelination of the nervous system: mechanisms and functions. Annu Rev Cell Dev Biol 30:503-33

Visembryo. nda. 26 wks post ovulation: lungs begin to produce surfactant. The Visible Embryo. www.visembryo.comOpens a new window [Accessed March 2020]

Visembryo. ndb. 30 wks post ovulation: lungs begin to produce surfactant. The Visible Embryo. www.visembryo.comOpens a new window [Accessed March 2020]

Visembryo. ndc. 32 wks post ovulation: fetus begins to develop immune system. The Visible Embryo. www.visembryo.comOpens a new window [Accessed March 2020]

Megan Rive

Megan Rive is a communication, content strategy and project delivery specialist. She was Babycenter editor for six years.

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