From the second edition (1989):
pregnant, a.2 (n.)
(ˈprɛgnənt) Also 5 -ante, 5–6 -aunt, pringnant, 6 preignant, -aunt. [ad. L. prægnāns, -ānt-em with child, pregnant; cf. F. prégnant (prégnante fem. in Rabelais 1550).
The OF. word was preins, preigne = It. pregno, L. type *prægnus; but in Eng. pregnaunt was used in 1413, and was app. common in the 15th c. in the transf. sense 3. It is remarkable that this should appear so much earlier than the literal sense. L. prægnāns has generally been explained as a ppl. form, from præ before + root gna- of gnāscor, gnātus to be born, a derivation favoured by the cognate prægnātio a making pregnant or being with child, and late L. prægnāre to be pregnant, prægnātus pregnant, and prægnātus (u-stem) pregnancy. On the other hand this does not explain the early collateral form prægnās, -ātem, (Plautus), and the connexion with root gna- is disputed by some: see Walde Latein. Etymol. Wörterbuch s.v.]

I. 1. That has conceived in the womb; with child or with young; gravid. Const. with, of (the offspring), by (the male parent).

1545 T. Raynalde Byrth Mankynde ii. vii. 86 Hypocrates sayth: The pregnant [edd. 1552–65 pregnaunt, ed. 1598 pregnate] Woman whiche hath Tenasmum for the most part aborteth. 1656 Blount Glossogr., Pregnant‥, great with child or young. 1665–6 Phil. Trans. I. 388 Pregnant Bitches‥at certain times of their gravidation. 1667 Milton P.L. ii. 779 My womb Pregnant by thee, and now excessive grown Prodigious motion felt. 1774 Goldsm. Nat. Hist. (1776) IV. 176 We are not certainly informed how long the females [seals] continue pregnant. a1827 Ld. Eldon in Powell's Devises (ed. 3) II. 360 The child with which A. M. is now pregnant. 1844 H. H. Wilson Brit. India II. 441 The widow of Ladhuba‥was pregnant at the time of her husband's assassination. 1899 Allbutt's Syst. Med. VIII. 298 Mental changes are common in pregnant women.

b. fig. (or in figurative context).

c1630 Milton Passion 56 And I‥Might think th'infection of my sorrows loud, Had got a race of mourners on som pregnant cloud. 1641 Hinde J. Bruen xxx. 93 One errour is a pregnant, and faithfull mother of many more. 1764 Goldsm. Trav. 138 The pregnant quarry teem'd with human form. 1873 Symonds Grk. Poets iii. 87 Cyrnus, this city is pregnant; but I fear that it will bring forth a man to chastise our evil violence.

c. fig. Big, laden, swelling; of a sail, bellying.

1648 Herrick Hesper., Oberon's Feast 23 A pure seed~pearle of infant dew, Brought and besweetned in a blew And pregnant violet. a1687 Cotton Winter x, With all her pregnant sails atrip.

2. transf. a. Of a plant or seed: Fertilized, capable of germinating; fruitful. Obs.

1669 Worlidge Syst. Agric. (1681) 329 Pregnant, full as a Bud, or Seed, or Kernel ready to sprout. 1759 tr. Duhamel's Husb. i. xv. (1762) 80 May prevent the grains being render'd pregnant. 1762–9 Falconer Shipwr. i. 361 There, rich with nectar, melts the pregnant vine.

b. Of the soil, etc.: Fertile, fruitful; prolific, teeming. Const. with. Obs.

1615 G. Sandys Trav. ii. 97 The fat and pregnant slime which it [the Nile] leaueth behind it. 1715 tr. Pancirollus' Rerum Mem. I. iv. xix. 231 An Isle‥call'd Marmora, very pregnant with Metals. 1762–9 Falconer Shipwr. ii. 161 The clouds, with ruin pregnant, now impend. 1789 Mrs. Piozzi Journ. France II. 68 This horrible volcano‥seems pregnant with wonders. 1796 Morse Amer. Geog. I. 614 Virginia is the most pregnant with minerals and fossils of any state in the Union.

II. In various mental or non-physical uses.

3. a. Of a person or his mind: Teeming with ideas, fertile, imaginative, inventive, resourceful, ready. Const. of, in, or to with inf. arch. or Obs.

1413 Pilgr. Sowle (Caxton 1483) iii. x. 57 Adam was pregnaunt of vnrightwisnesse and sool disbeysaunte. 1432–50 tr. Higden (Rolls) III. 467 Þe mynde of man is pregnante in a feire day, and feynte in a clowdy day. 1513 Bradshaw St. Werburge ii. 1204 Famous in victorye, preignant in wysdome. Ibid. 2024 Fyrst to maister Chaucer, and Ludgate sentencious, Also to preignaunt Barkley, nowe beyng religious, To inuentiue Skelton and poet laureate. a1591 H. Smith Serm. (1637) 509 Very pregnant to devise nevv shifts to keep in their almes. 1624 R. Skynner in Ussher's Lett. (1686) 352 The Jews have always been so ready and pregnant in the Scriptures, as that they need not cite the Book, Chapter, or Verse. 1632 Lithgow Trav. viii. 371 The exquisit ingeniosity of their best styles, and pregnant inuention. 1711 Steele Spect. No. 136 ⁋4 A Person of so pregnant a Fancy, that he cannot be contented with ordinary Occurrences. 1853 M. Arnold Scholar Gypsy iv. 34 The story of that Oxford scholar poor Of pregnant parts and quick inventive brain.

b. in pregnant wit, common in 16–17th c. arch.

1494 Fabyan Chron. vii. 652 A marchaunt, of pregnaunt wytte, and of good maner and speche. 1519 Interl. Four Elem. in Hazl. Dodsley I. 7 Divers pregnant wits be in this land. 1549 Chaloner Erasmus on Folly Mij, Who is he so pregnant witted that might grope out these misteries? [1572 Satir. Poems Reform. xxx. 71 Pringnant of wit, of policie but peir. 1589 Nashe Pref. Greene's Menaphon (Arb.) 17 His pregnant dexteritie of wit.] 1634 Heywood Maidenhead Lost i. Wks. 1874 IV. 106 Come, come, I know you haue a pregnant wit. c1660 South Serm., John vii. 17 (1715) I. 241 Nor did ever the most pregnant Wit in the World bring forth any Thing great,‥without some Pain and Travail.

c. esp. of young persons, or their faculties: Apt to conceive or apprehend, quick-witted, of unusual capacity, full of promise, promising. Obs.

1557 Order of Hospitalls Cviij, Suche of the children as be pregnant and very apt to learninge. 1612 Drayton Polyolb. vi. 223 Her apt and pregnant Youth sent hither yeere by yeere, Instructed in our Rites with most religious feare. 1635 R. Brathwait Arcad. Pr. ii. 180 Whom we no lesse truly than properly call the Muses minion, the conceits pregnantest darling. a1661 Fuller Worthies (1662) i. 239 She was a very pregnant Lady above her age, and died in her infancy when not full four years old. 1707 Chamberlayne Pres. St. Eng. iii. 425 Some of the most pregnant Lads are so good Proficients‥that they are sent to the University.

d. Apt to receive or be influenced; receptive; disposed, inclined, ready. Obs. (chiefly in Shakes.).

1601 Shakes. Twel. N. iii. i. 100 My matter hath no voice, Lady, but to your owne most pregnant and vouchsafed eare. 1602 —— Ham. iii. ii. 66 And crooke the pregnant Hindges of the knee. 1608 —— Per. iv. Prol. 44 And cursed Dioniza hath The pregnant instrument of wrath Prest for this blow. 1628 Donne Serm. xxix. (1640) 290 Christ places the Comfort of this Comforter, the Holy Ghost, in this, that he shall worke upon that pregnant faculty, the Memory.

e. Of hearing: Keen, sharp, acute. Obs. rare.

1607 Topsell Four-f. Beasts (1658) 209 Their hearing is most pregnant; for the Egyptians when they signifie hearing, picture a Hare; and for this cause we have shewed you already that their ears are long like horns.

4. Of words, symbolic acts, etc.: Full of meaning, highly significant; containing a hidden sense, implying more than is obvious, suggestive; also, †full of, replete with (something significant).

c1450 Pol. Poems (Rolls) II. 227 Discusse it with diligens, and telle iff hit be, This pagent is pringnant, sir Pilat, pardé. c1480 Henryson Test. Cres. 270 In breif sermone ane pregnant sentence wryte. a1626 Bacon Confess. Faith Wks. 1879 I. 338/2 The continual history of the old world, and church of the Jews‥is‥pregnant of a perpetual allegory and shadow of the work of the redemption to follow. 1659 Pearson Creed (1839) 104 The best of the Latins thought the Greek word so pregnant and comprehensive, that the Latin tongue had no single word able to express it. a1661 Fuller Worthies (1662) i. 133 His Epithetes were pregnant with Metaphors. 1838–9 Hallam Hist. Lit. III. iii. vii. §41. 378 The style is what was called pregnant, leaving much to be filled up by the reader's reflection. 1860 Westcott Introd. Study Gosp. vi. (ed. 5) 318 St. Mark compresses into this one pregnant sentence the central lesson of the trial. 1879 Farrar St. Paul II. 188 It is impossible I think in fewer words to give the full interpretation of this pregnant thesis.

b. Phrases.
pregnant construction, in Gram. or Rhet., a construction in which more is implied than the words express. pregnant negative, in Logic [L. propositio categorica negativa prægnans in Paulus Nicolettus Venetus, 15th c., Prantl IV. 129, note 545]: see quot. 1890. negative pregnant, in Law, a negative implying or involving an affirmative.

1607 Cowell Interpr., Negatiue pregnant,‥is a negatiue implying also an affirmatiue. As if a man being impleaded, to haue done a thing vpon such a day, or in such a place, denyeth that he did it modo & forma declarata: which implyeth neuer the lesse, that in some sort he did it. 1657 Burton's Diary (1828) II. 265 You put a negative pregnant upon a man, to say that sitting at the door is more profane than standing. 1818 Cruise Digest (ed. 2) IV. 552 This general denial amounts only to a denial of personal notice to herself, and is a kind of negative pregnant. 1890 Cent. Dict. s.v., Pregnant negative, a negative proposition affected by a reduplicative, exceptive, or other expression requiring special treatment in logic: thus, ‘no man, qua man, ever sleeps’ is a pregnant negative.

5. Fertile or fruitful in results; big with consequences; containing important issues; momentous.

1591 Florio 2nd Fruites Ep. Ded. 1 In this stirring time and pregnant prime of inuention when euerie bramble is fruitfull. a1674 Clarendon Surv. Leviath. (1676) 255 Error is naturally pregnant, and the more desperate it is, the more fruitful. 1783 Gouv. Morris in Sparks Life & Writ. (1832) I. 252 A critical business,‥pregnant with dangerous consequences. 1820 Combe Consol. (Chandos) 160 They hold a pregnant lie well told, Is worth at least its weight in gold.

b. Resultant, produced. Obs. nonce-use.

1596 Bacon Max. & Use Com. Law i. viii. (1636) 34 Any accessary before the fact is subject to all the contingencies pregnant of the fact, if they be pursuances of the same fact.

B. as n. A pregnant woman. rare.

1654 Whitlock Zootomia 284 Humane Policy‥forbeareth execution of a condemned Pregnant (or woman with Child). 1864 in Webster [citing Dunglison, who, however, in his entry app. intends the adj.]; and in mod. Dicts.

Hence †ˈpregnant v. trans., to render pregnant.

1652 Sparke Prim. Devot. (1660) 407 Pray'r‥Sometime descending, Pregnanteth the Womb Of Teeming Earth.