Moms, ketika kandungan Moms mencapai minggu ke 21, janin sudah tumbuh dengan baik dan bahkan kondisi fisiknya semakin proporsional mendekati sempurna.
Seperti yang dituliskan di baby2see.com, Moms. Dari kepala hingga tumit, janin memiliki panjang 27 cm, dan berat sekitar 360 gram.
Kalau Moms membaca artikel yang membahas perkembangan janin di minggu-minggu sebelumnya, Moms pasti tahu kalau sejak minggu ke 18, bertambahnya ukuran janin tidak begitu pesat. Setiap minggunya, berat janin hanya bertambah sekitar 10 gram. Moms tahu kenapa?
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Di situs lainnya, webmd.com, alasan pertumbuhan janin yang terlihat melambat itu adalah terjadinya pendewasaan organ-organ dalam janin. Di minggu ke 21, organ pencernaan janin berkembang lebih baik, dan sel darah merah mulai diproduksi di sumsum tulang belakangnya.
Perlu Moms ketahui bahwa di minggu ke 21, produksi sel darah merah oleh janin bisa jadi kabar baik sekaligus kabar buruk. Kabar buruknya, jika Moms memiliki sel darah merah golongan RH negatif, dan sel darah janin RH positif, lalu keduanya bertemu, maka Sel darah Moms akan mengira darah janin sebagai organisme invasif, dan menghancurkannya.
Untungnya, ada sebuah lapisan pemisah di antara janin dan sistem peredaran darah Moms.
Kesimpulannya, Moms. Pertumbuhan janin di minggu ke 21 terpusat pada penyempurnaan sistem metabolisme tubuh. Bertambahnya panjang serta berat badan kini tak lagi menjadi prioritas.
Oleh: Sahirul Taufiqurahman
(vem/rsk)

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