Real‐time ultrasonography as a clinical and management tool to monitor pregnancy in a chimpanzee breeding colony

Abstract

Accurate assessment of gestational age, date of parturition, and evaluation of placental abnormalities are essential to monitor obstetrical and fetal complications in captive chimpanzee (Pan troglodytes) breeding colonies. Since ultrasonography is a safe and noninvasive technique for monitoring chimpanzee pregnancies, we have developed a technique to estimate the date of parturition using the fetal biparietal diameter (BPD) of the skull from real-time ultrasonographic measurements. A formula for determining gestational age was based on analysis of data obtained from 62 pregnancies over an %year period. From this formula an estimated gestational age was calculated and compared with menstrual cycle data from the period near the time of the estimated date of conception (EDC). If the data from the scan and cycle history were in agreement within 7 days, the estimate date of conception was corrected to be 3 days prior to detumescence of the sex cycle phase. Lastly, the estimated date of parturition (EDP) was predicted to be 240 days after the EDC. To evaluate the utility of this prediction, we subsequently examined 13 chimpanzee pregnancies using the above technique and compared it to the actual date of parturition (ADP). Nine of the 13 chimpanzees delivered within 2 weeks of the EDP. In addition to estimating gestational age, ultrasonography may be a useful tool for evaluating fetal growth and placental abnormalities and assessing third trimester complications in chimpanzee pregnancies.

Fetal ultrasonography: biometric data from four African primate species

“…Interestingly, the shift observed between the curve drawn by Lee and by the authors may be explained by a different gestation length (240 days for Lee, 229 days for CIRMF). As our data are in accordance with those already published, BPD seems to be a good index of gestational age in chimpanzees, as in humans and baboons [9]. However, because of the flattening of the curve and the wider dispersion of values toward the end of pregnancy, BPD seems less predictive at the end than at the beginning of pregnancy [2].…”

“…However, the human curve has a steeper slope and clearly diverges from the chimpanzee and gorilla curves after 20 weeks of pregnancy. Struthers et al [16] and Lee et al [9] reported a linear increase in BPD in chimpanzees, while we obtained a polynomial curve. Also, the curve reported by Lee seemed slightly shifted relative to ours, while that of Struthers was almost entirely superposable (Fig.…”

“…The animals were aged from 10 to 37 years and parity ranged from 0 to six. The date of conception was known for eight gestations, for the others, the time of fecundation was calculated from the mean duration of gestation observed in the colony [15] (229 days) which is in concordance with the data of Keeling and Roberts [8] (227 days), Lee et al [9] (230 days) and Tutin [17] (228 days).…”

“…In contrast, even though it also requires anesthesia, ultrasonography is both safe and non‐invasive. It can be used to determine the date of conception and gestational age, to estimate the date of parturition, and to detect placental and fetal abnormalities [9]. Ultrasonographic measurement of fetal biometric parameters, a routine procedure in humans, has been applied to many non‐human primate species such as macaques [13], baboons [3, 6] and apes [9, 16, 18].…”

Fetal load and the evolution of lumbar lordosis in bipedal hominins

“…Because these features have a fundamental role in resisting shear force 14 , similar patterns of lumbar dimorphism in Australopithecus and Homo indicate that spinal shear was also a major challenge in australopiths in general, and especially for gravid females. Similarities in body size and life history between australopiths and chimpanzees suggest that term mass and duration of gestation for australopiths was chimpanzee-like (1,590 g at 230 days) 17,18 rather than human-like (3,200 g at 290 days) 19,20 . Even so, term mass of the australopithecine fetus would easily have exceeded the 40% load trigger of 1,200 g in human pregnancy for a substantial period of pregnancy, approximately the last trimester (Supplementary Information).…”