Embryonic, foetal and placental development in the Common marmoset monkey (Callithrix jacchus)

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Abstract
Embryonic. foetal and placental samples were taken at hysterotomy from timed and estimated stages of pregnancy. Timed pregnancies were sampled at least every 10 days, between days 30 and 140 of the 144‐day gestationTwo placental discs of similar size were present in all cases. Placental growth followed a sigmoid curve with the most rapid growth being found between 60 and 90 days. Placentae from triplet pregnancies were larger and heavier than those from twin pregnancies. A description of the external characteristics of embryos and foetuses showed clear‐cut differences between each 10‐day interval. Foetal body weight was measured after day 70 and the body weight increased most rapidly after day 100. Twins were heavier than triplets during late pregnancy and at birth. The major organs were weighed after day 80 and the largest increase in weight gain was usually found between days 120 and 140. Fifty percent of the birth (is. 140‐day) weight was achieved by day 70–80 for the placenta and by day 120–130 for the body and organ weights. With the exception of the brain and adrenals, the body and organ weights at birth were 10–20° of their ultimate adult weight. The crown‐rump length (C.R.L.) was measured after day 50. The maximum increments in growth were found between days 70 and 110 and there was no difference between twins and triplets during pregnancy or at birth. Nineteen other trunk, limb and head measurements were taken after day 90 of pregnancy and the maximum increments in growth were found between 90 and 120 days. At birth, the trunk and limb measurements were 40° and the head was 68° of the adult size. In all weight and linear measurements, the rate of growth, which is the increment per unit of weight or length. was most rapid during the earliest time‐period measured.